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Alcohol consumption in Cameroon is approximately twice the African average, and Makenene is a hotspot of Schistosoma mansoni infection in the country. Considering that both schistosomiasis mansoni and alcohol abuse can induce liver pathology, this study aimed to investigate the prevalence and risk factors of S. mansoni and alcohol abuse comorbidity in Makenene, Cameroon. A cross-sectional survey was conducted in Makenene, including 431 adults from four communities. Schistosoma mansoni was diagnosed using Kato-Katz (KK) and point-of-care circulating cathodic antigen (POC-CCA) tests. Participants were considered S. mansoni-positive if either test was positive. The Alcohol Use Disorders Identification Test (AUDIT) was used to determine the alcohol dependence score (ADS). Sociodemographic, behavioral, and environmental factors were also recorded. The prevalence of S. mansoni was 19.6% (95% CI: 15.7–24.0) by KK and 66.1% (95% CI: 58.8–73.3) by POC-CCA, yielding a prevalence of 34.6% (95% CI: 30.2–39.0) in the study population. The prevalence of alcohol abuse was 54.3% (95% CI: 49.4–58.7). S. mansoni infection and alcohol abuse comorbidity prevalence was 17.4% (95% CI: 13.9–21.1). Independent predictors of this comorbidity included the community of residence, with the risk being nearly fivefold higher in Baloua (AOR = 4.99; 95% CI: 2.36–10.56; p < 0.001) and over twofold higher in Carrière (AOR = 2.37; 95% CI: 1.19–4.70; p = 0.013). Furthermore, regular consumption of palm wine (AOR = 2.72; 95% CI: 1.39–5.34; p = 0.003) and beer (AOR = 2.00; 95% CI: 1.06–3.80; p = 0.032), as well as being aged 18–39 years (AOR = 1.88; 95% CI: 1.02–3.46; p = 0.042), were also identified as significant independent factors. This study confirms S. mansoni endemicity in Makenene and reveals a high prevalence of alcohol misuse, highlighting the comorbidity. These findings call for integrated interventions targeting both schistosomiasis transmission and harmful alcohol use.

Background: Schistosoma mansoni infection and chronic alcohol consumption are major public health concerns that predominantly affect the liver, yet their combined hepatic effects remain insufficiently understood. This study aimed to investigate the pathophysiological mechanisms associated with this co-exposure in an endemic setting in Cameroon. Methods: A cross-sectional analytical study was conducted in Makenéné, Cameroon, including 310 adults stratified by parasitic status and level of alcohol exposure. Infection was diagnosed using Kato-Katz and POC-CCA assays. Alcohol exposure was assessed using the Alcohol Use Disorders Identification Test (AUDIT). Hematological, liver function, oxidative, inflammatory, and fibrogenic profiles were evaluated. Results: Compared with alcohol abuse alone, combined S. mansoni infection and alcohol abuse was associated with reduced erythrocyte and platelet indices (p < 0.05), elevated activities of AST (p < 0.001), ALP (p < 0.01), GGT (p < 0.05), AST/ALT ratio (p < 0.001), and protein concentration (p < 0.001). Relative to schistosomiasis alone, the comorbidity was associated with higher ALT and AST (p < 0.01) and GGT (p < 0.05), but lower total protein (p < 0.05). Both schistosomiasis and alcohol abuse, independently, induced oxidative stress, evidenced by increased malondialdehyde levels (p < 0.001) and decreased catalase activity, GSH, and nitrite levels. This oxidative imbalance was exacerbated in co-exposed individuals who exhibited the lowest catalase activity (p < 0.01) and GSH concentration (p < 0.05). The comorbidity was also characterized by the lowest TNF-α levels (p < 0.05) and the highest TGF-β1 levels (p < 0.001). Procollagen type III N-terminal peptide (P3NP) peaked during S. mansoni infection (p < 0.001) but was less expressed during the comorbidity (p < 0.05). Both S. mansoni infection intensity and alcohol abuse correlate positively with transaminases and malondialdehyde, but negatively with nitrite, catalase, and TNF-α. Infection correlates positively with proteins, TGF-β1, IL-10, and P3NP, while alcohol abuse negatively correlates with IL-10 and SOD. Conclusion: S. mansoni infection and alcohol abuse comorbidity exacerbates liver injury beyond either condition alone, with increased liver enzymes, oxidative stress, immune imbalance, and fibrogenesis, highlighting the need for integrated public health strategies to reduce liver-related morbidity in endemic settings.

Ethnopharmacological relevance: Ozoroa pulcherrima Schweinf. (syn.: Heeria pulcherrrima Schweinf.) is a small shrub belonging to the family Anacardiaceae. In Africa, the stem and the leaves are used to treat dystocia, hyperthermia, and conjunctivitis, while the root is used to treat dysmenorrhea and intestinal helminthiasis. Aim of the study: The aim of this study was to assess the schistosomicidal, antioxidant and anti-inflammatory effects of the ethyl acetate fraction from O. pulcherrima roots methanolic extract (EAOp) on S. mansoni-induced liver pathology in mice. Additionally, its phytochemical composition was elucidated. Material and methods: The phytochemical characterization of EAOp was carried out by High-Performance Liquid Chromatography-Mass spectrometry (HPLC-MS). Total phenolic and flavonoid contents were also quantified in the fraction. S. mansoni-infected mice received daily and per os, for 28 days, EAOp at 200 or 400 mg/kg, starting from the 36th day post-infection. Praziquantel was used as reference drug. Uninfected-untreated, uninfected-treated and infected-untreated mice served as controls. At the 65th day post-infection mice were sacrificed and parasitological burden monitored. Transaminases, total bilirubin, and total proteins levels were determined in the plasma. Malondialdehyde (MDA), nitrites, superoxide dismutase (SOD), catalase (CAT) and reduced glutathione (GSH) levels were measured in the liver as biomarkers of the oxidative stress. Liver histology and morphometric analysis of granulomas were also conducted. Results: The HPLC-MS analysis data of EAOp revealed the presence of four triterpenes namely oleaterminaloic acid, hydroxyoleanolic acid, moronic acid, and oleanolic acid; a flavonoid dipentoxybenzoic acid and two alkaloids. Its total phenolic content was 76.46 ± 0.01 mg GAE/g and total flavonoid content 6.26 ± 0.31 mg rutin equivalent/g. The reductions of worm burden (48.89 and 75.56%), fecal egg count (77.76 and 69.52%) and egg load in the liver (65.33 and 77.18%) and intestine (78.06 and 84.63%) were significant after EAOp treatment. EAOp at all doses significantly (p < 0.001) reversed the increasing transaminases activities and total bilirubin level induced by the infection. A normalization of total proteins concentration was also recorded. Treatment of S. mansoni-infected mice with EAOp at 200 or 400 mg/kg resulted in a significant reduction (p < 0.001) of MDA concentration by 73.20% and 67.78% respectively. The level of nitrites which was reduced by the infection significantly increased after the treatment. EAOp significantly increased by 4.67 and 5.69-fold the CAT activity and by 126.67% the GSH level. Histologically, a significant reduction of the number (66.39 and 57.82%) and the volume (52.25 and 34.81%) of liver inflammatory granulomas was recorded after EAOp treatment at all doses. Conclusions: These results suggest that the liver pathology in S. mansoni infection is improved by EAOp which disclosed good schistosomicidal, antioxidant and anti-inflammatory activities. Its effects on the liver dysfunction and the hepatic oxidative stress were comparable to that of praziquantel. These findings justified the traditional use of O. pulcherrima for the treatment of intestinal helminthiasis. This fraction can be considered as a promising source for schistosomicidal agents.

Paragonimiasis, human lung fluke disease, is a foodborne anthropozoonosis caused by the trematodes assigned to Paragonimus and is regarded by the World Health Organization as a Neglected Tropical Disease (NTD). The life cycle of this medically important parasite centres on a complex freshwater biological community that includes two intermediate hosts: a mollusc and a decapod, usually a brachyuran. Although there is a perception that the biology, symptoms, diagnosis and treatment of Paragonimus is well understood, in reality, this is not the case, especially in Africa. Much remains unknown concerning the life-cycle of the parasite, its transmission, the current epidemiology of the disease, diagnosis and the effectiveness of treatment. Furthermore, cases of paragonimiasis may be misdiagnosed as resistant tuberculosis (TB) because of the similar pulmonary symptoms and no remission after anti TB therapy. The endemic foci of human paragonimiasis in Africa have been reported mainly in the forest zones of Upper Guinea (Liberia, Guinea and Ivory Coast) and Lower Guinea (Nigeria, Cameroon, Equatorial Guinea and Gabon). Despite the perceived medical importance of paragonimiasis, relatively little attention has been paid to this NTD since its discovery in Africa in the 1960s. This review focuses on the current understanding of the life cycle and transmission of Paragonimus in Africa, discusses its diagnosis and public health importance and highlights many outstanding gaps in the knowledge that still exist for this NTD.

In Cameroon, there is a national programme engaged in the control of schistosomiasis and soil-transmitted helminthiasis. In certain locations, the programme is transitioning from morbidity control towards local interruption of parasite transmission. The volcanic crater lake villages of Barombi Mbo and Barombi Kotto are well-known transmission foci and are excellent context-specific locations to assess appropriate disease control interventions. Most recently they have served as exemplars of expanded access to deworming medications and increased environmental surveillance. In this paper, we review infection dynamics through time, beginning with data from 1953, and comment on the short- and long-term success of disease control. We show how intensification of local control is needed to push towards elimination and that further environmental surveillance, with targeted snail control, is needed to consolidate gains in preventive chemotherapy as well as empower local communities to take ownership of interventions.

Background: The macerate of Sida pilosa aerial parts is used empirically for the treatment of intestinal helminthiasis. Previous studies have shown that Sida pilosa aqueous extract (SpAE) has schistosomicidal, antioxidant, anti-inflammatory and anti-fibrotic activities in Schistosoma mansoni infection. This study was designed to evaluate the effect of SpAE on the granulomatous inflammation induced by S. mansoni in the liver and the intestine of mice by histomorphometry; as well as on the gastrointestinal motility. Methods: To study the effect of SpAE on the liver and intestine histomorphometry and on the gastrointestinal motility, SpAE was administered at 200 mg/kg per os to S. mansoni-infected mice for 4 weeks. Praziquantel was used as reference drug. Prior to carrying out sacrifice, a batch of mice was subjected to gastrointestinal transit evaluation with 3% charcoal meal. After sacrifying another batch of mice, we performed histological and morphometric analyses of the liver and the ileum. We measured the following: total proteins, transaminases, malondialdehyde, nitrites, superoxide dismutase, catalase and reduced glutathione. The effect of SpAE (4, 8, 16 and 32 mg/mL) on the ileum contractile activity was evaluated either in the absence or in the presence of pharmacological blockers. Results: SpAE induced a significant reduction of hepatosplenomegaly and intestine enlargement. The number of granulomas was reduced by 52.82% in the liver and 52.79% in the intestine, whereas the volume of hepatic granulomas decreased by 48.76% after SpAE treatment. SpAE also reduced (p < 0.001) the ileal muscular layer thickness. The levels of total proteins, transaminases, malondialdehyde, nitrites, superoxide dismutase, catalase and reduced glutathione were restored after treatment of infected mice with SpAE. A normalization of the gastrointestinal transit was also recorded after SpAE treatment. The effect of SpAE on intestinal motility was mediated via intracellular and extracellular calcium mobilization. Conclusion: Our findings provide evidence that SpAE improves granulomatous inflammation induced by S. mansoni both in the liver and in the intestine, as well as it re-establishes normal gastrointestinal transit. SpAE may be used for the development of alternative medicine against S. mansoni infection.

Ethnopharmacological relevance: Ozoroa pulcherrima Schweinf. (syn.: Heeria pulcherrrima Schweinf.) is a small shrub belonging to the family Anacardiaceae. In Africa, the stem and the leaves are used to treat dystocia, hyperthermia, and conjunctivitis, while the root is used to treat dysmenorrhea and intestinal helminthiasis. Aim of the study: The aim of this study was to assess the schistosomicidal, antioxidant and anti-inflammatory effects of the ethyl acetate fraction from O. pulcherrima roots methanolic extract (EAOp) on S. mansoni- induced liver pathology in mice. Additionally, its phytochemical composition was elucidated. Material and methods: The phytochemical characterization of EAOp was carried out by High-Performance Liquid Chromatography-Mass spectrometry (HPLC-MS). Total phenolic and flavonoid contents were also quantified in the fraction. S. mansoni-infected mice received daily and per os, for 28 days, EAOp at 200 or 400 mg/kg, starting from the 36th day post-infection. Praziquantel was used as reference drug. Uninfected-untreated, uninfected-treated and infected-untreated mice served as controls. At the 65th day post-infection mice were sacrificed and parasitological burden monitored. Transaminases, total bilirubin, and total proteins levels were determined in the plasma. Malondialdehyde (MDA), nitrites, superoxide dismutase (SOD), catalase (CAT) and reduced glutathione (GSH) levels were measured in the liver as biomarkers of the oxidative stress. Liver histology and morphometric analysis of granulomas were also conducted. Results: The HPLC-MS analysis data of EAOp revealed the presence of four triterpenes namely oleaterminaloic acid, hydroxyoleanolic acid, moronic acid, and oleanolic acid; a flavonoid dipentoxybenzoic acid and two alkaloids. Its total phenolic content was 76.46 ± 0.01 mg GAE/g and total flavonoid content 6.26 ± 0.31 mg rutin equivalent/g. The reductions of worm burden (48.89 and 75.56%), fecal egg count (77.76 and 69.52%) and egg load in the liver (65.33 and 77.18%) and intestine (78.06 and 84.63%) were significant after EAOp treatment. EAOp at all doses significantly (p < 0.001) reversed the increasing transaminases activities and total bilirubin level induced by the infection. A normalization of total proteins concentration was also recorded. Treatment of S. mansoni-infected mice with EAOp at 200 or 400 mg/kg resulted in a significant reduction (p < 0.001) of MDA concentration by 73.20% and 67.78% respectively. The level of nitrites which was reduced by the infection significantly increased after the treatment. EAOp significantly increased by 4.67 and 5.69-fold the CAT activity and by 126.67% the GSH level. Histologically, a significant reduction of the number (66.39 and 57.82%) and the volume (52.25 and 34.81%) of liver inflammatory granulomas was recorded after EAOp treatment at all doses. Conclusions: These results suggest that the liver pathology in S. mansoni infection is improved by EAOp which disclosed good schistosomicidal, antioxidant and anti-inflammatory activities. Its effects on the liver dysfunction and the hepatic oxidative stress were comparable to that of praziquantel. These findings justified the traditional use of O. pulcherrima for the treatment of intestinal helminthiasis. This fraction can be considered as a promising source for schistosomicidal agents.

Adult schistosomes live in the blood vessels and cannot easily be sampled from humans, so archived miracidia larvae hatched from eggs expelled in feces or urine are commonly used for population genetic studies. Large collections of archived miracidia on FTA cards are now available through the Schistosomiasis Collection at the Natural History Museum (SCAN). Here we describe protocols for whole genome amplification of Schistosoma mansoni and Schistosome haematobium miracidia from these cards, as well as real time PCR quantification of amplified schistosome DNA. We used microgram quantities of DNA obtained for exome capture and sequencing of single miracidia, generating dense polymorphism data across the exome. These methods will facilitate the transition from population genetics, using limited numbers of markers to population genomics using genome-wide marker information, maximising the value of collections such as SCAN.

The mainstay of current schistosomiasis control is preventive chemotherapy (PC) with praziquantel, targeted toward school-aged children, based on the disease endemicity within a subset of surveyed schools, which are classified using parasitological prevalence and intensity of infections. However, it is well known that the current conventional mapping design for schistosomiasis has shown several limitations and may lead to several uncertainties and misclassification of some districts and their eligibility for PC. These inaccuracies prevent successful PC coverage of all populations that need treatment and, therefore, jeopardise the achievement of schistosomiasis elimination. Our recent studies have revealed that precision mapping of schistosomiasis is an essential requirement to move from disease control toward interruption of schistosome transmission in sub-Saharan Africa. As schistosomiasis is a focal disease geographically, having a high-resolution map is necessary if current or future interventions are to be targeted accordingly. Precision mapping is defined as conducting sampling at a much finer geographical resolution, potentially examining all schools within every subunit in each implementation unit in order to eliminate the errors caused by missing the focal variation in schistosomiasis prevalence. Conclusion: Precision mapping of schistosomiasis gives high-resolution information at the local level. By increasing the map granularity and spatial resolution, precision mapping provides the best evidence-based data to guide intensified interventions in targeted transmission zones and allows for a better and rational utilization of the donated praziquantel and available resources. We therefore believe that it is a promising and innovative tool to shrink the map of schistosomiasis and accelerate the move toward the elimination of schistosomiasis.

Background: Barombi Kotto, Cameroon serves as a reference location for assessing intervention strategies against Schistosoma haematobium. Methods: As part of a pilot study, the whole community was treated with praziquantel, inclusive of pre-school-age children (PSAC) and their mothers. One year later, egg-patent infections were reassessed and water contact patterns of 12 pairs of PSAC and their mothers were measured with global positioning system (GPS) data loggers. Results: A substantial reduction in general infection prevalence, from 44.8% to 12.2%, was observed but certain PSAC and mothers continued to have egg-patent infections. Analysis of GPS data demonstrated similar water contact levels between the child and mother groups, although certain individuals were numerical outliers. Conclusions: This study shows the potential of GPS data loggers to clarify the at-risk status of PSAC and mothers.

Aim: The schistosomicidal activity of C. umbellatum leaves aqueous extract has been previously demonstrated. The present study was performed to establish the acute and sub-chronic oral toxicity profile of C. umbellatum leaves aqueous extract in mice. Methods: For acute oral toxicity study, C. umbellatum leaves aqueous extract (CuAE) was administered per os to female mice at a single dose of 2000 mg/kg. Animals were observed for 14 days in order to identify signs of toxicity or death. In the repeated dose 28-day oral toxicity study, the extract was administered daily and per os to female and male mice at doses of 200, 400 and 800 mg/kg for 28 consecutive days. A satellite group was also set up. Body weight was measured weekly. Hematological, biochemical and histopathological parameters were analyzed. Results: CuAE at 2000 mg/kg produced no sign of toxicity or mortality. In the sub-chronic toxicity study, no mortality, no significant change of the body weight, the relative organ weights and the hematological parameters were recorded in all treated mice. CuAE at 400 mg/kg significantly increased transaminases activities in male mice. Except for creatinine and HDL-cholesterol which concentrations increased after administration of CuAE at 800 mg/kg, the levels of others biochemical markers didn't change. Histopathological abnormalities found in the kidneys were reversible. Conclusion: These results indicated that the LD50 of CuAE is greater than 2000 mg/kg and CuAE, therefore, belongs to the category five of relatively non-toxic substances. From the sub-chronic toxicity study, the no-observed-adverse-effect level (NOAEL) of CuAE for both male and female mice was considered to be 200 mg/kg/day.

Schistosomiasis affects over 200 million people worldwide and accounts for an estimated 1.9 million disability-adjusted life years (DALYs) annually, with 90% of the burden currently concentrated in Africa. The last decade has witnessed an extraordinary surge of advocacy and funding for neglected tropical diseases (NTDs), including schistosomiasis. Large-scale schistosomiasis control is now implemented in 30 countries in Africa, funded primarily through support from USAID and DFID, private philanthropic funds from the END Fund and through GiveWell recommendations, and leveraging praziquantel donations from Merck KGaA. However, the number of people still requiring treatment remains daunting. The aim of current public health strategies for schistosomiasis is to decrease morbidity through preventive chemotherapy (PC). Periodic large-scale administration of the drug praziquantel focusing on the school-aged population and high-risk adults aims to reduce the prevalence and intensity of infection. Refocus on morbidity control: It is timely to refocus schistosomiasis programs (both intestinal and urogenital, caused by Schistosoma mansoni and S. haematobium, respectively) in Africa on improving strategies for long-term and sustainable morbidity control until a decision to pursue elimination can be made. With realistic, evidence-based targets, programs can more readily measure progress and adapt approaches. Conclusion: Considerable financial and human resources and long-term political commitment will likely be needed to achieve elimination of schistosomiasis transmission in Africa. The current mainstay of schistosomiasis programs, PC, will need to be complemented by other control interventions such as increased access to clean water, improved sanitation and hygiene, communications to support behavior change, environmentally friendly snail control, and a vaccine. We recommend taking this opportunity to refocus on strategic investments in long-term morbidity control.

The aim of this study was to determine the influence of steeping of cassava tubers on the structure of Benthic Macroinvertebrates (BM) community in Central African Republic (CAR) in relation to the physicochemical quality of the water of Pala stream. The data were collected from May 2015 to April 2016 on a monthly frequency in 5 selected sampling stations of the upstream towards the downstream on the river. The physicochemical analyses were carried out using standard methods while the benthic macro fauna was collected using a net with a mesh size of 150 m on a total surface of approximately 6 m2 per station. The physicochemical analyses revealed a satisfactory water quality of the stations not located downstream from the point of steeping of the cassava tubers and a deterioration of the ecological quality in the stations located downstream from the point of steeping. A total of 2982 Benthic Macroinvertebrates, belonging to 79 taxa were identified and counted. Arthropods were the most diversified with 54 taxa and more abundant (53.11 %), followed by Molluscs (23 taxa, 37.79 % of abundance) and Annelids (2 taxa, 9.10 % of abundance). The station P5 in the potamal area, which is the only station not directly located downstream from the steeping of the cassava tubers harbours the majority of Arthropods, dominated by Insects. In fact, the presence of oligotrophic characteristic crustaceans is confirming the auto purification capacity of the river due to a weak disturbance related to anthropic activities. In the rhythral and potamal stations downstream from the steeping of the cassava tubers, the strong abundance of Molluscs and the presence of Annelids, all polluotolerants, indicate the water quality degradation due to this practice of steeping.

Rubella virus (RV) infection is responsible of an unresolved clinical complication that affects newborns and children. During the first trimester of pregnancy, it often causes severe birth defects known as congenital rubella syndrome (CRS). This study reports the seroprevalence of the RV-specific IgM and IgG antibodies, its relationship with the duration of pregnancy and past history of abortion in pregnant women at Yaoundé in order to help strategies to eliminate rubella and to prevent Congenital Rubella Syndrome (CRS) in Cameroon. Four Hundred (400) pregnant women were screened for rubella immunoglobulins G (IgG) and M (IgM), using the chemiluminescent microparticle immunoassay for the detection of IgG and IgM antibodies on the ARCHITECT i system at the Laboratory of Medical Analysis of Pasteur Institute, Senegal. Out of the 400 pregnant women tested, 367 (91.75%) were positive for RV-IgG while only 5 (1.25%) were positive for RV-IgM. A higher number of pregnant women in the first trimester of pregnancy tested positive for IgG (91.8%). None of the possible risk factors were significantly associated with infection. The presence of rubella RV-IgM and RV-IgG in pregnant women predisposes babies to CRS and emphasizes on the initiation of a vaccination policy of those who are susceptible in Cameroon.

Introduction: Worldwide, millions of individuals are affected by neglected tropical diseases (NTDs). They are frequently the poorest and most marginalised members of society. Their living conditions, among other things, make them susceptible to such diseases. Historically, several large-scale treatment programmes providing mass drug administrations (MDAs) were carried out per single disease but over the last decade there has been an increasing trend towards co-implementation of MDA activities given the resources used for such programmes are often the same. The COUNTDOWN multicountry studies focus on scaled-up implementation of integrated control strategies against four diseases: lymphatic filariasis, onchocerciasis, schistosomiasis and soil-transmitted helminthiasis. The objective of the COUNTDOWN economic study is to assess the multicountry implementation of control interventions in terms of equity, impact and efficiency. Methods: The health economic study uses different analytical methods to assess the relationship between NTDs and poverty and the cost-effectiveness of different large-scale intervention options. Regression analysis will be used to study the determinants of NTD occurrence, the impact of NTDs on poverty, factors that hinder access to MDAs and the effect of NTDs on quality-of-life of those affected, including disability. Cost-effectiveness analyses of various integration methods will be performed using health economic modelling to estimate the cost and programme impact of different integration options. Here, cost-effectiveness ratios will be calculated, including multivariate sensitivity analyses, using Bayesian analysis. Ethics and dissemination: Ethics approval has been received both at the Liverpool School of Tropical Medicine and in all participating countries. Results of the various substudies will be presented for publication in peer-reviewed journals.

On 29 September 2017, the World Health Organization (WHO) published a new Guideline on the implementation of preventive chemotherapy (PC) programmes for the control of soil-transmitted helminthiasis (STH) infections. The document supersedes two WHO publications that, in addition to STH, simultaneously addressed the control of schistosomiasis, onchocerciasis, and lymphatic filariasis (LF) by the coordinated implementation of regular, systematic, large-scale interventions. With recent advances in understanding of the epidemiology of STH and the changing funding landscape, the NTDs community has eagerly awaited new guidance from WHO on PC, to set and safeguard the public health stage beyond the original targets defined by the WHO NTD roadmap of 2012. Regrettably, the opportunity to build on the previous momentum has been missed. We have identified five critical areas where the 2017 WHO guideline does not provide the necessary leadership: (i) absence of guidance on the most urgent current issues (school-based vs community-wide PC, drug combinations, new diagnostics, monitoring anthelminthic resistance, new prevalence thresholds, morbidity vs elimination end-game targets); (ii) no mention of the need to accurately monitor drug coverage and individual compliance; (iii) insufficient discussion of available deworming data; (iv) absence of WHO recommendations for schistosomiasis, onchocerciasis, and LF, as the new guideline only considers STH; (v) inadequate pragmatic guidance for programme managers on implementation, monitoring, and evaluation of PC STH programmes. Conclusions: The new 2017 guideline is, in our view, a disappointing return to the past pre-2004 instead of looking at the future beyond 2020. We suggest that WHO urgently sets up a working group to produce a second edition of the 2006 PC in human helminthiasis manual for health professionals and programme managers. Until such time, we advise the NTD community to continue to implement the 2006 manual and 2011 guide.

Schistosomiasis is a waterborne parasitic disease in sub-Saharan Africa, particularly common in rural populations living in impoverished conditions. With the scale-up of preventive chemotherapy, national campaigns will transition from morbidity- to transmission-focused interventions thus formal investigation of actual or expected declines in environmental transmission is needed as 'end game' scenarios arise. Surprisingly, there are no international or national guidelines to do so in sub-Saharan Africa. Our article therefore provides an introduction to key practicalities and pitfalls in the development of an appropriate environmental surveillance framework. In this context, we discuss how strategies need to be adapted and tailored to the local level to better guide and support future interventions through this transition. As detection of egg-patent infection in people becomes rare, careful sampling of schistosome larvae in freshwater and in aquatic snails with robust species-specific DNA assays will be required. Appropriate metrics, derived from observed prevalence(s) as compared with predetermined thresholds, could each provide a clearer insight into contamination- and exposure-related dynamics. Application could be twofold, first to certify areas currently free from schistosomiasis transmission or second to red-flag recalcitrant locations where extra effort or alternative interventions are needed.

Schistosomiasis is a water borne parasitic disease of global importance and with ongoing control the disease endemic landscape is changing. In sub-Saharan Africa, for example, the landscape is becoming ever more heterogeneous as there are several species of Schistosoma that respond in different ways to ongoing preventive chemotherapy and the inter-sectoral interventions currently applied. The major focus of preventive chemotherapy is delivery of praziquantel by mass drug administration to those shown to be, or presumed to be, at-risk of infection and disease. In some countries, regional progress may be uneven but in certain locations there are very real prospects to transition from control into interruption of transmission, and ultimately elimination. To manage this transition requires reconsideration of some of the currently deployed diagnostic tools used in surveillance and downward realignment of existing prevalence thresholds to trigger mass treatment. A key challenge will be maintaining and if possible, expanding the current donation of praziquantel to currently overlooked groups, then judging when appropriate to move from mass drug administration to selective treatment. In so doing, this will ensure the health system is adapted, primed and shown to be cost-effective to respond to these changing disease dynamics as we move forward to 2020 targets and beyond.

Background
Onchocerciasis and lymphatic filariasis (LF) are endemic in Equatorial Guinea with notable variations in disease incidence between island and mainland regions. Historically, efforts to control and map these diseases were concentrated in Bioko Island, where loiasis is absent, allowing for targeted onchocerciasis interruption strategies. With the cessation of onchocerciasis transmission on Bioko and no reported cases on Annobon island, assessing the transmission status in the previously unaddressed mainland region has become imperative. Mapping efforts in mainland Equatorial Guinea have proven low to moderate level of transmission for LF and onchocerciasis, although the results so far have not been very conclusive. The current study aims to update the prevalence estimates for onchocerciasis and LF in mainland Equatorial Guinea using various diagnostic techniques.
Methods
This is the first cross-sectional study carried out to estimate the prevalence of onchocerciasis and LF in the mainland area of Equatorial Guinea, from September to December 2019, based on the combination of skin snip biopsies, thick blood smears, laboratory serological tests (ELISA tests for the detection of IgG4 antibodies against Onchocerca volvulus recombinant antigen Ov16 and Wuchereria bancrofti recombinant antigen Wb123) and molecular laboratory tests. Frequencies and prevalence rates, along with 95% confidence intervals for interval estimation of a binomial proportion, were computed.
Results
The overall onchocerciasis seroprevalence calculated for the study was 0.3% (95% CI: 0.1 to 0.5%). Microscopic examination of skin biopsies from the eight individuals seropositive for Ov16, out of the 3951 individuals initially tested, revealed no O. volvulus microfilariae. However, DNA extracted from one skin snip was successfully amplified, with subsequent sequencing confirming the presence of O. volvulus. Among the 3951 individuals, 182 were found to have anti-Wb123 antibodies, suggesting exposure to W. bancrofti, with an estimated seroprevalence of 4.6% (95% CI: 4.0 to 5.3%). Microscopy and Filaria-real time-PCR (F-RT-PCR) analysis for W. bancrofti were negative across all samples.
Conclusions
The findings indicate that onchocerciasis may no longer constitutes a public health problem in Equatorial Guinea, positioning the country on the verge of achieving elimination. Additionally, the mapped prevalence of LF will facilitate the formulation of national strategies aimed at eradicating filariases countrywide.

Schistosomiasis remains an important public health issue, with a large number of cases reported across sub-Saharan Africa, and parts of Asia and Latin America. China was once highly endemic, but has made substantial progress and is moving towards elimination of schistosomiasis. Meanwhile, despite long-term, repeated, school-based chemotherapy in many African countries, more than 90% of all schistosomiasis cases are concentrated in Africa, and hence, this continent constitutes the key challenge for schistosomiasis control. Opportunities and issues for international collaboration in the fight against schistosomiasis are outlined with a focus on China's experiences, including the role of public health authorities and intersectoral collaboration, use of new and effective snail control approaches and diagnostic tools adapted to the specific stage of control, as well as the strengthening of risk mapping and surveillance-response mechanisms. Training courses targeting African governmental officials and professionals, coupled with field visits of African scientists and control programme managers to China, and vice versa, are considered important for improved schistosomiasis control and elimination. The crucial question remains whether the Chinese experience can be translated and applied in African countries to improve the effectiveness of health interventions and scale-up.

Ethnopharmacological relevance: Sida pilosa Retz (Malvaceae) is a plant used in Africa for the treatment of intestinal helminthiasis, lower abdominal pains and dysmenorrhea. Aim of the study: In order to determine the potential use of S. pilosa in the treatment of schistosomiasis mansoni, we evaluated the schistosomicidal, antioxidant and anti-fibrotic properties of the aqueous extract and the n-butanol fraction of its aerial parts. Material and methods: S. pilosa aqueous extract (SpAE) at 100, 200 and 400 mg/kg and n-butanol fraction (SpBF) at 50, 100 and 200 mg/kg were administered per os to Schistosoma mansoni-infected mice for 4 weeks. Praziquantel (100 mg/kg × 5 days) was used as reference drug. After sacrifice, worm burden and egg count, transaminases and proteins levels were evaluated. Malondialdehyde (MDA), lipid hydroperoxydes (LOOH), catalase (CAT), superoxide dismutase (SOD), eosinophil peroxidase (EPO) and myeloperoxidase (MPO) were also measured. The anti-fibrotic effect of the plant was evaluated by the determination of hydroxyproline and γ-interferon (IFN-γ). Results: The treatment of S. mansoni-infected mice by SpAE or SpBF resulted in a moderate reduction of worm burden and egg load in the liver and intestine. Both SpAE and SpBF significantly reversed the increasing liver proteins, MDA, LOOH and CAT levels induced by the infection. Moreover, SOD activity was improved by SpAE and SpBF. Schistosomiasis mansoni considerably increased the EPO (p<0.001) and MPO activities (p<0.001). SpAE treatment significantly reduced EPO and MPO activities at all doses. SpBF failed to reduce the increasing MPO and decreased EPO only at the highest dose. S. mansoni-infection induced an increase in hydroxyproline content (p<0.001) and a decrease in IFN-γ level (p<0.001). Both SpAE and SpBF significantly reduced hepatic hydroxyproline content, while only SpAE (p<0.05) improved IFN-γ level. Conclusion: These results suggest that the liver pathology in schistosomiasis mansoni is improved by S. pilosa aqueous extract, which disclosed a moderate schistosomicidal, but strong antioxidant and anti-fibrotic activities. The n-butanol fraction was however less active than the aqueous extract.

Among the species of schistosomes infecting humans, Schistosoma haematobium is responsible for the largest number of infections in sub-Saharan Africa with an estimated 112 million people infected with this species. Schistosoma haematobium has been shown to be able to interbreed with its closely related sister species, resulting in hybridisation affecting the epidemiology of these parasites. Schistosoma haematobium, Schistosoma mansoni, Schistosoma guineensis and Schistosoma bovis have all been reported in Cameroon. In this study, S. haematobium samples from 8 villages in Cameroon were molecularly analysed to identify hybrid schistosomes. Methods: PCR-RFLP analyses of the second internal transcribed spacer (ITS-2) of ribosomal DNA (rDNA) were carried out on schistosomes worms which had been isolated from 8 villages; Bessoum, Ouro-Doukoudje, Djalingo-Kapsiki, Gounougou, Njombe, Penja, Loum and Mbafam. Results: An ITS-2 DNA fragment of 501 bp was amplified from all the isolates of S. haematobium group and analysed. The TaqI enzymatic digestion of the ITS-2 DNA fragment revealed 3 different band profiles: Profile A (typical of S. haematobium) which constituted of 2 bands (158 bp and 199 bp); Profile B (typical of S. bovis and S. guineensis) which constituted of 2 bands (199 bp and 230 bp); and Profile C (probably an intermediate form) which contained all 3 bands (158 bp, 199 bp and 230 bp). One isolate from naturally infected snail (Bulinus globosus) collected from the rice field in Bessoum shown profile C. Tree worms from isolates collected from Mbafam and Djalingo-Kapsiki presented profile B, characteristic of probable hybrids. All other isolates presented with profile A, corresponding to the naturally occurring Schistosoma haematobium species. Conclusions: Our data provides an indication of hybrid S. haematobium group occurring in Cameroon and could serve as a reminder to inform control programs. Such findings highlight the constant need for the continued monitoring of the geographic spread and emergence of such hybrid forms.

Background: Schistosomiasis affects more than 200 million individuals, mostly in sub-Saharan Africa, but empirical estimates of the disease burden in this region are unavailable. We used geostatistical modelling to produce high-resolution risk estimates of infection with Schistosoma spp and of the number of doses of praziquantel treatment needed to prevent morbidity at different administrative levels in 44 countries. Methods: We did a systematic review to identify surveys including schistosomiasis prevalence data in sub-Saharan Africa via PubMed, ISI Web of Science, and African Journals Online, from inception to May 2, 2014, with no restriction of language, survey date, or study design. We used Bayesian geostatistical meta-analysis and rigorous variable selection to predict infection risk over a grid of 1 155 818 pixels at 5 × 5 km, on the basis of environmental and socioeconomic predictors and to calculate the number of doses of praziquantel needed for prevention of morbidity. Findings: The literature search identified Schistosoma haematobium and Schistosoma mansoni surveys done in, respectively, 9318 and 9140 unique locations. Infection risk decreased from 2000 onwards, yet estimates suggest that 163 million (95% Bayesian credible interval [CrI] 155 million to 172 million; 18·5%, 17·6–19·5) of the sub-Saharan African population was infected in 2012. Mozambique had the highest prevalence of schistosomiasis in school-aged children (52·8%, 95% CrI 48·7–57·8). Low-risk countries (prevalence among school-aged children lower than 10%) included Burundi, Equatorial Guinea, Eritrea, and Rwanda. The numbers of doses of praziquantel needed per year were estimated to be 123 million (95% CrI 121 million to 125 million) for school-aged children and 247 million (239 million to 256 million) for the entire population. Interpretation: Our results will inform policy makers about the number of treatments needed at different levels and will guide the spatial targeting of schistosomiasis control interventions. Funding: European Research Council, China Scholarship Council, UBS Optimus Foundation, and Swiss National Science Foundation.

Background: Interest is growing in predictive risk mapping for neglected tropical diseases (NTDs), particularly to scale up preventive chemotherapy, surveillance, and elimination efforts. Soil-transmitted helminths (hookworm, Ascaris lumbricoides, and Trichuris trichiura) are the most widespread NTDs, but broad geographical analyses are scarce. We aimed to predict the spatial and temporal distribution of soil-transmitted helminth infections, including the number of infected people and treatment needs, across sub-Saharan Africa. Methods: We systematically searched PubMed, Web of Knowledge, and African Journal Online from inception to Dec 31, 2013, without language restrictions, to identify georeferenced surveys. We extracted data from household surveys on sources of drinking water, sanitation, and women's level of education. Bayesian geostatistical models were used to align the data in space and estimate risk of hookworm, A lumbricoides, and T trichiura over a grid of roughly 1 million pixels at a spatial resolution of 5 × 5 km. We calculated anthelmintic treatment needs on the basis of WHO guidelines (treatment of all school-aged children once per year where prevalence in this population is 20–50% or twice per year if prevalence is greater than 50%). Findings: We identified 459 relevant survey reports that referenced 6040 unique locations. We estimate that the prevalence of hookworm, A lumbricoides, and T trichiura among school-aged children from 2000 onwards was 16·5%, 6·6%, and 4·4%. These estimates are between 52% and 74% lower than those in surveys done before 2000, and have become similar to values for the entire communities. We estimated that 126 million doses of anthelmintic treatments are required per year. Interpretation: Patterns of soil-transmitted helminth infection in sub-Saharan Africa have changed and the prevalence of infection has declined substantially in this millennium, probably due to socioeconomic development and large-scale deworming programmes. The global control strategy should be reassessed, with emphasis given also to adults to progress towards local elimination.

Background: The intensive use of Praziquantel for the treatment of schistosomiasis has raised concerns about the possible emergence of drug-resistant schistosomes. As drug treatment is an important feature of schistosome control programs, the search for alternative drugs is therefore a priority. The aim of this study was to assess the schistosomicidal, hepatoprotective and antioxidant activities of the methanolic fraction from Clerodendrum umbellatum Poir leaves aqueous extract. Methods: A phytochemical screening of the fraction of C. umbellatum was conducted. The fraction was administered orally and daily to Schistosoma mansoni-infected mice (BALB/c) from the 36th day post-infection for 28 days at 100, 200 and 400 mg/kg. Praziquantel (500 mg/kg) was used as reference drug. Non-infected and infected-untreated mice served as controls. All mice were sacrificed at 65th day post-infection. Body weight, liver/body and spleen/body weights, as well as worm burden, fecal egg count, liver and intestine egg load were determined. In the plasma, levels of total protein, transaminases (ALT, AST), alkaline phosphatase and total bilirubin were monitored to assess the possibility of liver damage. Malondialdehyde (MDA), catalase (CAT) and glutathione (GSH) levels were measured in the liver as biomarkers of the oxidative stress. Results: The phytochemical analysis of the fraction from C. umbellatum aqueous leaves extract revealed the presence of alkaloids, flavonoids, cardiac glycosides, phenols, saponins, tannins and terpenoids. The worm burden, fecal egg count and egg load in the liver and intestine of infected mice treated with the fraction were significantly (p < 0.001) fewer than in infected-untreated mice. Only the highest-fraction dose reduced the worm and egg burdens in a similar way as praziquantel. Hepatosplenomegaly induced by S. mansoni infection was reduced by the treatment. The liver function on infected mice was ameliorate after administration of the fraction by significant reduction of ALT activity (35.43 to 45.25%) and increase of total protein level (44.79 to 70.03%). The methanolic fraction of C. umbellatum prevents the elevated MDA level induced by the infection while significant increase in catalase activity (297.09 to 438.98%) and glutathione level (58.23 to 95.88%) were observed after treatment. Conclusions: This study disclosed the schistosomicidal, hepatoprotective and antioxidant activities of the methanolic fraction from C. umbellatum leaves aqueous. These fraction's activities were similar to those of praziquantel. This fraction can be considered as a promising source for schistosomicidal agents.

Urinary schistosomiasis and geohelminths are endemic in Cameroon and continues to pose public health challenges especially in inhabitants of rural areas. This study was conducted in an attempt to re-assess the epidemiological data (prevalence and intensity of infection) of the prevalence of urinary schistosomiasis and geohelminths among school children in Kekem, local government areas, West-Cameroon. The study was carry out in 4 schools and, in each of the selected schools, stool and urine samples were collected from 180 school children. Single Kato-Katz technique was employed to determine presence of geohelminth; urine filtration technique was employed to determine presence of Schistosoma haematobium eggs in urine. An overall prevalence of 1.7% for urinary schistosomiasis was observed among the 180 children examined. No significant difference in prevalence was observed between school, sex and across age group examined (p>0.05). The prevalence rates of urinary schistosomiasis in each school were 6.5% in Kekem 44; 2% in Mbafam and 0% in Mboebo and Plateau B. This shows that there is a significant decrease, due to previous treatments which took place in this area. This provided the positive intervention of the schistosomiasis control. An overall prevalence rates of Soil Transmitted Helminths were 17.8% for Ascaris lumbricoïdes, 17.2% for Trichuris trichiura and 1.7% for Necator americanus. For each parasite, no significant difference in prevalence was observed between school, sex and across age group.

The regular administration of the anthelminthic drug praziquantel (PZQ) to school-aged children (and other high-risk groups) is the cornerstone of schistosomiasis control. Whilst the performance of PZQ against single schistosome species infections is well-known, performance against mixed species infections is less so, as are patterns of re-infection following treatment. To address this, a study using a double treatment with PZQ, administered at 40 mg/kg spaced by 3 weeks, took place in two mixed intestinal-urogenital schistosomiasis foci in northern Cameroon (Bessoum and Ouro-Doukoudje) and in one single intestinal schistosomiasis infection focus (Makenene). A total of just under 1000 children were examined and the Schistosoma-infected children were re-examined at several parasitological follow-ups over a 1-year period posttreatment. Overall cure rates against Schistosoma spp. in the three settings were good, 83.3% (95% confidence interval (CI)=77.9-87.7%) in Bessoum, 89.0% (95% CI=79.1-94.6%) in Ouro Doukoudje, and 95.3% (95% CI=89.5-98.0%) in Makenene. Interestingly, no case of mixed schistosome infection was found after treatment. Cure rates for S. mansoni varied from 99.5% to 100%, while that for S. haematobium were considerably lower, varying from 82.7% to 88.0%. Across transmission settings, patterns of re-infection for each schistosome species were different such that generalizations across foci were difficult. For example, at the 6-month follow-up, re-infection rates were higher for S. haematobium than for S. mansoni with re-infection rates for S. haematobium varying from 9.5% to 66.7%, while for S. mansoni, lower rates were observed, ranging between nil and 24.5%. At the 12-month follow-up, re-infection rates varied from 9.1% to 66.7% for S. haematobium and from nil to 27.6% for S. mansoni. Alongside these parasitological studies, concurrent malacological surveys took place to monitor the presence of intermediate host snails of schistosomiasis. In the two northern settings, three species of Bulinus (intermediate host snail of S. haematobium) were collected; i.e. Bulinus truncatus, B. globosus and B. senegalensis, however, Biomphalaria pfeifferi (intermediate host snail of S. mansoni) was much rarer despite repeated and intensive searching and was suggestive of limited local transmission potential of S. mansoni during this time. While this study highlights that performance of PZQ was satisfactory in this region, with somewhat greater impact upon intestinal than urogenital schistosomiasis, the dynamics of local transmission are shown, however, to be complex.

Like many African cities affected by urban schistosomiasis, Maroua in the Far North Region of Cameroon has a moderate level of schistosomiasis transmission, as indicated by human infections. This study was designed to identify and map some potential transmission sites of schistosomiasis in Maroua. Water ponds were surveyed for snail intermediate host of schistosome and mapped using a handheld Global Positioning Systems (GPS). Snail status was assessed via cercaria shedding procedure. The vegetation cover, human water contact activities and some physico-chemical characteristics of the water including pH, temperature, salinity, total dissolve solute (TDS) were measured and documented. Twenty two water ponds were surveyed and 21 of them were found to have at least one of the two identified schistosome snail host species. A total of 658 specimens of snails were collected: 57.45% B. senegalensis and 42.55% B. globosus. Eleven water ponds were found to have both snail host and the 10 other have single species (8 with B. senegalensis and 2 with B. globosus). Ten (1.56%) of the 642 snails were found to shed Schistosoma cercariae: 2.21% in B. senegalensis and 0.71% in B. globosus and they were not significantly different (χ² = 1.431, p = 0.232). The presence of B. senegalensis and B. globosus (two known intermediate snail host of S. haematobium) snail and their infections with Schistosoma suggest possible local transmission of human schistosomiasis in Maroua. Exposure to these water environments may pose infection risk to general population, in particular children who seem to have greater water contact.

Background: Robust reference values for fecal egg count reduction (FECR) rates of the most widely used anthelmintic drugs in preventive chemotherapy (PC) programs for controlling soil-transmitted helminths (STHs; Ascaris lumbricoides, Trichuris trichiura, and hookworm) are still lacking. However, they are urgently needed to ensure detection of reduced efficacies that are predicted to occur due to growing drug pressure. Here, using a standardized methodology, we assessed the FECR rate of a single oral dose of mebendazole (MEB; 500 mg) against STHs in six trials in school children in different locations around the world. Our results are compared with those previously obtained for similarly conducted trials of a single oral dose of albendazole (ALB; 400 mg). Methodology: The efficacy of MEB, as assessed by FECR, was determined in six trials involving 5 830 school children in Brazil, Cambodia, Cameroon, Ethiopia, United Republic of Tanzania, and Vietnam. The efficacy of MEB was compared to that of ALB as previously assessed in 8 841 school children in India and all the above-mentioned study sites, using identical methodologies. Principal findings: The estimated FECR rate [95% confidence interval] of MEB was highest for A. lumbricoides (97.6% [95.8; 99.5]), followed by hookworm (79.6% [71.0; 88.3]). For T. trichiura, the estimated FECR rate was 63.1% [51.6; 74.6]. Compared to MEB, ALB was significantly more efficacious against hookworm (96.2% [91.1; 100], p<0.001) and only marginally, although significantly, better against A. lumbricoides infections (99.9% [99.0; 100], p = 0.012), but equally efficacious for T. trichiura infections (64.5% [44.4; 84.7], p = 0.906). Conclusions/significance: A minimum FECR rate of 95% for A. lumbricoides, 70% for hookworm, and 50% for T. trichiura is expected in MEB-dependent PC programs. Lower FECR results may indicate the development of potential drug resistance.

We evaluated a commercial point-of-care circulating cathodic antigen (POC-CCA) test for assessing Schistosoma mansoni infection prevalence in areas at risk. Overall, 4,405 school-age children in Cameroon, Côte d'Ivoire, Ethiopia, Kenya, and Uganda provided urine for POC-CCA testing and stool for Kato-Katz assays. By latent class analysis, one POC-CCA test was more sensitive (86% versus 62%) but less specific (72% versus ~100%) than multiple Kato-Katz smears from one stool. However, only 1% of POC-CCA tests in a non-endemic area were false positives, suggesting the latent class analysis underestimated the POC-CCA specificity. Multivariable modeling estimated POC-CCA as significantly more sensitive than Kato-Katz at low infection intensities (< 100 eggs/gram stool). By linear regression, 72% prevalence among 9–12 year olds by POC-CCA corresponded to 50% prevalence by Kato-Katz, whereas 46% POC-CCA prevalence corresponded to 10% Kato-Katz prevalence. We conclude that one urine POC-CCA test can replace Kato-Katz testing for community-level S. mansoni prevalence mapping.

Schistosoma mansoni is a widespread human helminth and causes intestinal schistosomiasis in 54 countries, mainly across Africa but also in Madagascar, the Arabian Peninsula and the neotropics. The geographical range of this parasite relies on the distribution of certain species of freshwater pulmonate snails of the genus Biomphalaria. Whilst S. mansoni is known to exhibit high population diversity the true extent of this diversity is still to be fully elucidated as sampling of this taxon progressively accrues. Here a DNA 'barcoding' approach is taken using sequence analysis of a 450bp region within the mitochondrial cox1 gene to assess the genetic diversity within a large number of S. mansoni larval stages collected from their natural human hosts across sub-Saharan Africa. Five hundred and sixty one individual parasite samples were examined from 22 localities and 14 countries. Considerable within-species diversity was found with 120 unique haplotypes splitting geographically into five discrete lineages. The highest diversity was found in East Africa with samples forming three of the five lineages. Less diversity was found in the Far and Central Western regions of Africa with haplotypes from the New World showing a close affinity to the Far Western African S. mansoni populations supporting the hypothesis of a colonisation of South America via the West African slave trade. The data are discussed in relation to parasite diversity and disease epidemiology.

We conducted the first meta-analysis of ten Schistosoma haematobium (one published and nine unpublished) and eight Schistosoma mansoni (two published and six unpublished) microsatellite datasets collected from individual schistosome-infected school-children across six sub-Saharan Africa countries. High levels of genetic diversity were documented in both S. haematobium and S. mansoni. In S. haematobium populations, allelic richness did not differ significantly between the ten schools, despite widely varying prevalences and intensities of infection, but higher levels of heterozygote deficiency were seen in East than in West Africa. In contrast, S. mansoni populations were more diverse in East than West African schools, but heterozygosity levels did not vary significantly with geography. Genetic structure in both S. haematobium and S. mansoni populations was documented, at both a regional and continental scale. Such structuring might be expected to slow the spread to new areas of anti-schistosomal drug resistance should it develop. There was, however, limited evidence of genetic structure at the individual host level, which might be predicted to promote the development or establishment of drug resistance, particularly if it were a recessive trait. Our results are discussed in terms of their potential implications for the epidemiology and evolution of schistosomes as well as their subsequent control across sub-Saharan Africa.

The geographical ranges of most species, including many infectious disease agents and their vectors and intermediate hosts, are assumed to be constrained by climatic tolerances, mainly temperature. It has been suggested that global warming will cause an expansion of the areas potentially suitable for infectious disease transmission. However, the transmission of infectious diseases is governed by a myriad of ecological, economic, evolutionary and social factors. Hence, a deeper understanding of the total disease system (pathogens, vectors and hosts) and its drivers is important for predicting responses to climate change. Here, we combine a growing degree day model for Schistosoma mansoni with species distribution models for the intermediate host snail (Biomphalaria spp.) to investigate large-scale environmental determinants of the distribution of the African S. mansoni-Biomphalaria system and potential impacts of climatic changes. Snail species distribution models included several combinations of climatic and habitat-related predictors; the latter divided into "natural" and "human-impacted" habitat variables to measure anthropogenic influence. The predictive performance of the combined snail-parasite model was evaluated against a comprehensive compilation of historical S. mansoni parasitological survey records, and then examined for two climate change scenarios of increasing severity for 2080. Future projections indicate that while the potential S. mansoni transmission area expands, the snail ranges are more likely to contract and/or move into cooler areas in the south and east. Importantly, we also note that even though climate per se matters, the impact of humans on habitat play a crucial role in determining the distribution of the intermediate host snails in Africa. Thus, a future contraction in the geographical range size of the intermediate host snails caused by climatic changes does not necessarily translate into a decrease or zero-sum change in human schistosomiasis prevalence.

Background: The three major soil-transmitted helminths (STH) Ascaris lumbricoides, Trichuris trichiura and Necator americanus/Ancylostoma duodenale are among the most widespread parasites worldwide. Despite the global expansion of preventive anthelmintic treatment, standard operating procedures to monitor anthelmintic drug efficacy are lacking. The objective of this study, therefore, was to define the efficacy of a single 400 milligram dose of albendazole (ALB) against these three STH using a standardized protocol. Methodology/Principal Findings: Seven trials were undertaken among school children in Brazil, Cameroon, Cambodia, Ethiopia, India, Tanzania and Vietnam. Efficacy was assessed by the Cure Rate (CR) and the Fecal Egg Count Reduction (FECR) using the McMaster egg counting technique to determine fecal egg counts (FEC). Overall, the highest CRs were observed for A. lumbricoides (98.2%) followed by hookworms (87.8%) and T. trichiura (46.6%). There was considerable variation in the CR for the three parasites across trials (country), by age or the pre-intervention FEC (pre-treatment). The latter is probably the most important as it had a considerable effect on the CR of all three STH. Therapeutic efficacies, as reflected by the FECRs, were very high for A. lumbricoides (99.5%) and hookworms (94.8%) but significantly lower for T. trichiura (50.8%), and were affected to different extents among the 3 species by the pre-intervention FEC counts and trial (country), but not by sex or age. Conclusions/Significance: Our findings suggest that a FECR (based on arithmetic means) of >95% for A. lumbricoides and >90% for hookworms should be the expected minimum in all future surveys, and that therapeutic efficacy below this level following a single dose of ALB should be viewed with concern in light of potential drug resistance. A standard threshold for efficacy against T. trichiura has yet to be established, as a single-dose of ALB is unlikely to be satisfactory for this parasite.

Background: The Kato-Katz thick smear (Kato-Katz) is the diagnostic method recommended for monitoring large-scale treatment programs implemented for the control of soil-transmitted helminths (STH) in public health, yet it is difficult to standardize. A promising alternative is the McMaster egg counting method (McMaster), commonly used in veterinary parasitology, but rarely so for the detection of STH in human stool. Methodology/Principal Findings: The Kato-Katz and McMaster methods were compared for the detection of STH in 1,543 subjects resident in five countries across Africa, Asia and South America. The consistency of the performance of both methods in different trials, the validity of the fixed multiplication factor employed in the Kato-Katz method and the accuracy of these methods for estimating 'true' drug efficacies were assessed. The Kato-Katz method detected significantly more Ascaris lumbricoides infections (88.1% vs. 75.6%, p<0.001), whereas the difference in sensitivity between the two methods was non-significant for hookworm (78.3% vs. 72.4%) and Trichuris trichiura (82.6% vs. 80.3%). The sensitivity of the methods varied significantly across trials and magnitude of fecal egg counts (FEC). Quantitative comparison revealed a significant correlation (Rs >0.32) in FEC between both methods, and indicated no significant difference in FEC, except for A. lumbricoides, where the Kato-Katz resulted in significantly higher FEC (14,197 eggs per gram of stool (EPG) vs. 5,982 EPG). For the Kato-Katz, the fixed multiplication factor resulted in significantly higher FEC than the multiplication factor adjusted for mass of feces examined for A. lumbricoides (16,538 EPG vs. 15,396 EPG) and T. trichiura (1,490 EPG vs. 1,363 EPG), but not for hookworm. The McMaster provided more accurate efficacy results (absolute difference to 'true' drug efficacy: 1.7% vs. 4.5%). Conclusions/Significance: The McMaster is an alternative method for monitoring large-scale treatment programs. It is a robust (accurate multiplication factor) and accurate (reliable efficacy results) method, which can be easily standardized.

Schistosomiasis is a water-based disease that is believed to affect over 200 million people with an estimated 97% of the infections concentrated in Africa. However, these statistics are largely based on population re-adjusted data originally published by Utroska and colleagues more than 20 years ago. Hence, these estimates are outdated due to large-scale preventive chemotherapy programs, improved sanitation, water resources development and management, among other reasons. For planning, coordination, and evaluation of control activities, it is essential to possess reliable schistosomiasis prevalence maps. We analyzed survey data compiled on a newly established open-access global neglected tropical diseases database (i) to create smooth empirical prevalence maps for Schistosoma mansoni and S. haematobium for individuals aged ≤20 years in West Africa, including Cameroon, and (ii) to derive country-specific prevalence estimates. We used Bayesian geostatistical models based on environmental predictors to take into account potential clustering due to common spatially structured exposures. Prediction at unobserved locations was facilitated by joint kriging. Our models revealed that 50.8 million individuals aged ≤20 years in West Africa are infected with either S. mansoni, or S. haematobium, or both species concurrently. The country prevalence estimates ranged between 0.5% (The Gambia) and 37.1% (Liberia) for S. mansoni, and between 17.6% (The Gambia) and 51.6% (Sierra Leone) for S. haematobium. We observed that the combined prevalence for both schistosome species is two-fold lower in Gambia than previously reported, while we found an almost two-fold higher estimate for Liberia (58.3%) than reported before (30.0%). Our predictions are likely to overestimate overall country prevalence, since modeling was based on children and adolescents up to the age of 20 years who are at highest risk of infection. We present the first empirical estimates for S. mansoni and S. haematobium prevalence at high spatial resolution throughout West Africa. Our prediction maps allow prioritizing of interventions in a spatially explicit manner, and will be useful for monitoring and evaluation of schistosomiasis control programs.

Soil-transmitted helminthiasis (STH) occur throughout the developing world and remain a major public health problem in the poorest communities with enormous consequences on health and development of school-aged and preschool children. The extent of the problem has long been neglected because these diseases rarely kill at a young age, due to their insidious and chronic nature. Today there exists a momentum and an unprecedented opportunity for a cost-effective control of these neglected tropical diseases. The control of these diseases has become a priority on the agenda of many governments, donors and international agencies, which provides important funding opportunities for STH control through integration and co-implementation of control interventions. In the era of preventive chemotherapy, the intensification of mass administration of anthelminthic drugs will result in epidemiological changes of STH transmission levels, with a rapid increase of light infections as far as control programmes are successful. As consequence, the current diagnostic tools may not be always appropriate and may therefore require adaptation or development of alternative assays adapted to the stage of control. This paper reviews aspects relevant to diagnosis and appropriate tools for accurate surveillance and monitoring of STH control programmes and drug efficacy. Prospects, opportunities and challenges for the control are discussed.

Clerodendrum umbellatum Poir (Verbenaceae) is traditionally used in Cameroon for the treatment of many diseases including intestinal helminthiasis. This study was undertaken to assess the in vivo antischistosomal activity of its leaves aqueous extract on a Schistosoma mansoni mice model and to determine the most effective dose of this extract. Mice showing a patent infection of S. mansoni were daily treated with C. umbellatum leaves aqueous extract at the doses of 40, 80 or 160 mg/kg body weight for 14 days. Seven days after administration of the extract, schistosomicidal activity was evaluated on the liver and spleen weights, faecal eggs releasing, liver egg count and worm burden. Treatment using C. umbellatum leaves aqueous extract resulted in an important reduction in faecal egg output by 75.49% and 85.14% for 80 mg/kg and 160 mg/kg of the extract respectively. These reduction rates did not differ significantly from the 100% obtained in the group of infected mice treated with 100 mg/kg of praziquantel. C. umbellatum leaves aqueous extract was lethal to S. mansoni worm. A 100% reduction rate was recorded in the group of infected mice treated with 160 mg/kg of the extract, as well as in praziquantel-treated mice. An amelioration of the hepatosplenomegaly was noticed in both the extract-treated mice and the praziquantel-treated mice. From these results, we can conclude that C. umbellatum leaves aqueous extract demonstrated schistosomicidal properties in S. mansoni model at doses of at least 80 mg/kg body weight.

The objective of this study was to evaluate the antischistosomal activity of the aqueous extract of Sida pilosa Retz (Malvaceae) on Schistosoma mansoni-infected mice and its toxicity profile. Sixty days post infection, animals were treated orally with the extract at 40, 80 and 160 mg/kg/day, for fourteen consecutive days. Unique administration of doses ranging from 4 to 20 g/kg were used to assess acute toxicity while doses of 400, 800 and 1600 mg/kg/day for 8 weeks were used for sub-acute toxicity. One week after treatment, comparisons of body, liver and spleen weights, egg load and worm recovery were carried out between untreated and treated groups. Treatment with S. pilosa aqueous extract resulted in a significant reduction in egg-laying of at least 82% and in worms recovering of at least 88%. A significant reduction of hepatomegaly and splenomegaly (p < 0.001) were also seen in all treated-animals. The LD50 of S. pilosa aqueous extract was greater than 20 g/kg and neither haematological nor biochemical parameters were modified after administration of the extract for eight weeks. These results indicate that S. pilosa aqueous extract exhibits antischistosomal activity in S. mansoni-infected mice and is toxicologically safe.

Schistosomiasis and soil-transmitted helminthiasis occur throughout the developing world and remain a major public health problem in the poorest communities with enormous consequences for development. The extent of the problem has long been neglected because these diseases rarely kill at a young age and also because of their insidious nature. Today there exists a momentum and an unprecedented opportunity for a cost-effective control of these neglected tropical diseases. The control of these diseases has become a priority on the agenda of many governments, donors and international agencies. This paper highlights the progress made and future control activities in Cameroon and Côte d'Ivoire, where schistosomiasis and soil-transmitted helminthiasis control measures have been implemented over the past decade with limited budgets. In Cameroon, deworming activities were increased to encompass all ten regions in 2007 as a result of a co-ordinated effort of the Ministry of Health and the Ministry of Education with national and international partners. In Côte d'Ivoire, focal control activities were achieved with support from various partners. Prospects, opportunities and challenges for the control of neglected tropical diseases in these two countries are discussed.

Treatment with praziquantel (PZQ) has become virtually the sole basis of schistosomiasis control in sub-Saharan Africa and elsewhere, and the drug is reviewed here in the context of the increasing rate that it is being used for this purpose. Attention is drawn to our relative lack of knowledge about the mechanisms of action of PZQ at the molecular level, the need for more work to be done on schistosome isolates that have been collected recently from endemic areas rather than those maintained in laboratory conditions for long periods, and our reliance for experimental work mainly on Schistosoma mansoni, little work having been done on S. haematobium. There is no evidence that resistance to PZQ has been induced in African schistosomes as a result of its large-scale use on that continent to date, but there is also no assurance that PZQ and/or schistosomes are in any way unique and that resistant organisms will not be selected as a result of widespread drug usage. The failure of PZQ to produce complete cures in populations given a routine treatment should therefore solicit considerable concern. With few alternatives to PZQ currently available and/or on the horizon, methods to monitor drug-susceptibility in African schistosomes need to be devised and used to help ensure that this drug remains effective for as long a time as possible.

In Cameroon, schistosomiasis and geohelminthiases are important public-health problems (Tchuem Tchuenté et al., 2003), especially among school-aged children, who represent the most affected subpopulation (Ratard et al., 1990; Brooker et al., 2000). The highest prevalences of human infection with both Schistosoma haematobium and S. mansoni are observed in the three northern regions of the country whereas the geohelminths tend to be most common in the south (Ratard et al., 1990; Brooker et al., 2000). The last large-scale survey of the distribution of human schistosomiasis in Cameroon was carried out more than 20 years ago, in 1986 (Ratard et al., 1990). At that time, both urinary schistosomiasis caused by S. haematobium and intestinal schistosomiasis caused by S. mansoni were observed in the schoolchildren of the North region (Fig. 1), at prevalences of 32% and 16%, respectively (Ratard et al., 1990). In 2000, during a survey carried out in 10 schools in the Lagdo district of the North region (none of which was surveyed in 1986), 70.5% of the schoolchildren investigated had urinary schistosomiasis and 30.8% had the intestinal disease (Cunin et al., 2003). Many villagers investigated in the mid 1980s in this region of Cameroon (C. M. Ndamkou, unpubl. obs.) showed ‘ectopic’ excretion of schistosome eggs (i.e. they were found to be excreting S. haematobium eggs in their stools and/or S. mansoni eggs in their urine). Similarly, when Cunin et al. (2003) investigated 11 villages in the area of Bessoum in 1999–2001, 3% of the urine samples they investigated were positive for S. mansoni eggs. In most African countries affected by schistosomes and geohelminths, a general lack of resources is a serious obstacle to the systematic identification of those areas where interventions against such parasites would best be implemented. Unfortunately, field surveys of these infections are time- and staff-consuming activities, especially when they are based on a parasitological diagnosis and classical sampling methods. Use of lot quality-assurance sampling (LQAS), which is not intended to measure the prevalence of a character but only to decide whether or not a ‘lot’ is ‘acceptable’ (according to a pre-determined, threshold number of ‘defective’ individuals and a pre-determined level of risk), allows smaller sample sizes than those needed in traditional sampling schemes. In the measurement of the endemicity of schistosomiasis, the LQAS method has already been found reliable and easy to use, in communities in both Madagascar (Rabarijaona et al., 2003) and Uganda (Brooker et al., 2005). The main objective of the present study was to use the LQAS method in mapping the distribution of human schistosomiasis in the North province of Cameroon, to help identify the most effective control policy in this area.

Single-strand conformation polymorphism (SSCP) analysis of the second internal transcribed spacer (ITS2) of nuclear ribosomal DNA provides a molecular tool for the identification of Schistosoma haematobium, Schistosoma guineensis and the hybrids of these two species. This molecular tool was utilized to provide a detailed analysis of the interactions between S. haematobium and S. guineensis in hybrid zones of Loum, Littoral Province, Cameroon. Individual hybrid schistosomes were identified within the natural populations collected from Loum in 1990, 1999 and 2000, which would have been misidentified as S. haematobium using solely morphological and sequence criteria. This study indicates the complexities of the hybridization between S. haematobium and S. guineensis and emphasizes the importance of assessing morphological, biological and molecular data to gain insights into the interaction of these two species over time.

The relationship between habitat stability, demography, and population genetic structure was explored by comparing temporal microsatellite variability spanning a decade in two closely-related hermaphroditic freshwater snails from Cameroon, Bulinus forskalii and Bulinus camerunensis. Although both species show similar levels of preferential selfing, microsatellite analysis revealed significantly greater allelic richness and gene diversity in populations of the highly endemic B. camerunensis compared to those of the geographically-widespread B. forskalii. Additionally, B. camerunensis populations showed significantly lower spatial genetic differentiation, higher dispersal rates, and greater temporal stability compared to B. forskalii populations over a similar spatial scale. This suggests that a more stable demography and greater gene flow account for the elevated genetic diversity observed in this geographically-restricted snail. This contrasts sharply with a metapopulation model (which includes extinction/contraction, recolonization/expansion, and passive dispersal) invoked to account for population structuring in B. forskalii. As intermediate hosts for medically important schistosome parasites, these findings have ramifications for determining the scale at which local adaptation may occur in the coevolution of these snails and their parasites.

Schistosomiasis occurs throughout the developing world and remains a major public health problem in the poorest communities with enormous consequences for development. More than 200 million people are infected and this poverty-related disease is highly prevalent in sub-Saharan Africa. The extent of the problem has long been neglected because the disease rarely kills and due to its insidious nature, signs and symptoms are taken seriously only after permanent impairment has occurred. Moreover, as many other poverty-related communicable diseases, schistosomiasis has been overshadowed by other health priorities. Today schistosomiasis control is a priority on the agenda of many governments, donors and international agencies. A momentum as well as an unprecedented opportunity do exist for cost-effective action. Importantly, the renewed impetus for schistosomiasis control throughout sub-Saharan Africa reinforces the need for operational research to improve our understanding of the disease. The strengthening of the national capacity in endemic countries, a greater commitment of governments and communities from these developing countries, and an efficient stakeholder coordination are vital for a successful and durable control. The paper highlights the current opportunities and challenge for schistosomiasis control for the 21st century. By working all together, we have a great opportunity to take up the challenge and to improve the health of the poor.

Previously assumed to be monogamous, the mating system of schistosomes has been the subject of some debate since recent findings have shown that change of mate can occur among these parasites. Here, Louis-Albert Tchuem Tchuenté, Vaughan R. Southgate, Claude Combes and Joseph Jourdane review progress made in the understanding of the mating behaviour of schistosomes, and highlight the importance of mating systems in the dynamics of natural transmission of schistosomiasis

Malacological surveys carried out in the early 1970s in water bodies of the Kinshasa area, Lower Zaire (Democratic Republic of Congo), showed the appearance of a Biomphalaria species which was identified as Biomphalaria camerunensis. In 1976, other surveys confirmed the presence of the species in several sites and showed numerous infected snails with Schistosoma mansoni, demonstrating for the first time an active transmission of the parasite responsible of the intestinal schistosomiasis in this area. The most recent malacological sampling was carried out by one of us in 1994 in Mangungu River and revealed the presence of apparently the same snail species. However, conchological, anatomical and molecular studies showed that this snail may be considered as an introduced neotropical species, B. tenagophila. To our knowledge, this is the second example of the introduction of a neotropical snail host of schistosomes into Africa.

The hermaphroditic freshwater snail Bulinus forskalii acts as intermediate host for the trematode Schistosoma guineensis, an agent of human intestinal schistosomiasis. Despite the medical importance of this snail, little is known about its mating system, even though this influences the epidemiology of schistosomiasis. Therefore, a parent-offspring analysis was carried out to elucidate its mating system. Eleven highly polymorphic microsatellites generated multilocus genotypes, enabling parentage assignment to all of the 432 offspring reared from 28 pairs of laboratory-bred B. forskalii. Ninety percent of progeny were of uniparental origin, and only six pairs (21% of parents) produced mixed clutches of crossed and selfed progeny. No pair reproduced exclusively by outcrossing. These results provide compelling evidence that B. forskalii has a mixed mating system dominated by uniparental reproduction, in agreement with indirect assessments from studies of population genetic structure and inbreeding effects. This reproductive strategy may be pivotal to the persistence of B. forskalii in its patchy, temporally unstable habitats, as well as helping it to cope with its parasitic burden.

Schistosoma mansoni is the most widespread of the human-infecting schistosomes, present in 54 countries, predominantly in Africa, but also in Madagascar, the Arabian Peninsula, and the Neotropics. Adult-stage parasites that infect humans are also occasionally recovered from baboons, rodents, and other mammals. Larval stages of the parasite are dependent upon certain species of freshwater snails in the genus Biomphalaria, which largely determine the parasite's geographical range. How S. mansoni genetic diversity is distributed geographically and among isolates using different hosts has never been examined with DNA sequence data. Here we describe the global phylogeography of S. mansoni using more than 2500 bp of mitochondrial DNA (mtDNA) from 143 parasites collected in 53 geographically widespread localities. Considerable within-species mtDNA diversity was found, with 85 unique haplotypes grouping into five distinct lineages. Geographical separation, and not host use, appears to be the most important factor in the diversification of the parasite. East African specimens showed a remarkable amount of variation, comprising three clades and basal members of a fourth, strongly suggesting an East African origin for the parasite 0.30–0.43 million years ago, a time frame that follows the arrival of its snail host. Less but still substantial variation was found in the rest of Africa. A recent colonization of the New World is supported by finding only seven closely related New World haplotypes which have West African affinities. All Brazilian isolates have nearly identical mtDNA haplotypes, suggesting a founder effect from the establishment and spread of the parasite in this large country.

Approximately 80% of the 200 million people infected with schistosomiasis inhabit sub-Saharan Africa, and the annual mortality is estimated to be 280,000. Praziquantel is the drug of choice in the treatment of schistosomiasis and pregnant women may now be treated. It was agreed at the World Health Assembly in 2001 that at least 75% of school-aged children in high burden areas should be treated for schistosomiasis and soil-transmitted helminth infections by 2010 to reduce morbidity. A grant from the Bill and Melinda Gates Foundation to the Schistosomiasis Control Initiative, Imperial College of Science, Technology and Medicine, London has enabled control programmes to be initiated in Uganda, Tanzania, Zambia, Burkina Faso, Niger and Mali. Additional programmes have recently commenced in Zanzibar with a grant from the Health Foundation to The Natural History Museum, London and in Cameroon. Combination treatment for schistosomiasis, gastrointestinal helminths and filariasis reduces costs of control programmes. The EC Concerted Action Group on 'Praziquantel: its central role in the chemotherapy of schistosome infection' met in Yaoundé Cameroon in 2004 to discuss recent developments in laboratory and field studies. The use of standard operating procedures will enable data on drug action on schistosomes produced in different laboratories to be compared. With the ever increasing use of praziquantel there is a possibility of the development of resistance by schistosomes to the drug, hence the necessity to explore the activities of other compounds. Artemether, unlike praziquantel, is effective against immature schistosomes. The effectiveness of mirazid, an extract of myrrh, is controversial as data from different laboratories are equivocal. It is suggested that an independent body such as the World Health Organization should determine whether mirazid should be used in the treatment of schistosomiasis.

Interactions between schistosomes are complex with some different species being able to mate and hybridize. The epidemiology of schistosomiasis in specific areas of South West Cameroon has evolved remarkably over 30 years as a result of hybridization between Schistosoma guineensis and S. haematobium. Morphological and biological data suggest that S. haematobium replaced S. guineensis in areas of Cameroon through introgressive hybridization. Data are reported on the use of single stranded conformational polymorphism (SSCP) analysis of the nuclear ribosomal second internal transcribed spacer (ITS2) of individual schistosomes from hybrid zones of Cameroon. The data show that since 1990 S. haematobium has completely replaced S. guineensis in Loum, with S. haematobium and the recombinants still present in 2000. This study illustrates the complexities of the dynamics between S. haematobium and S. guineensis in South West Cameroon.

Despite the limited reports of praziquantel resistance, the relative success of chemotherapy-based control programmes for schistosomiasis has prompted overdue efforts to expand the use of cheap, generic, praziquantel in sub-Saharan Africa. The likely impact of such programmes on the development and spread of praziquantel resistance is uncertain, but this possibility reinforces the need for monitoring the spectrum of praziquantel sensitivity of schistosome populations and for an improved knowledge of the precise targets for the action of the drug. The search for alternatives to praziquantel and other tools for control of schistosomiasis must continue.

The dose of praziquantel required to kill 50% of adult worms in vivo (i.e. the ED50) was estimated for nine different isolates of Schistosoma mansoni in infected mice. Four of the isolates were selected because they had not knowingly been in contact with the drug (i.e. they were putatively praziquantel-susceptible). Five putatively praziquantel-resistant isolates were chosen because they had been selectively bred for drug-resistance in the laboratory and/or had previously been shown to be relatively resistant to praziquantel in the field. The work was performed in three laboratories in different countries using pre-agreed and comparable experimental protocols. All four praziquantel-susceptible isolates had ED50s estimated to be <100 mg/kg (mean=70±7 SD; median=68), while all five putatively praziquantel-resistant isolates had estimated ED50s >100 mg/kg (mean=209±48 SD; median=192). Thus, the five praziquantel-resistant isolates, including two that had been subjected to drug pressure during more than 20 passages in mice, had drug ED50s that were approximately three times as great as those of the praziquantel-susceptible isolates. Two of the five isolates in the putatively resistant group had previously been passaged 15 or more times in mice without administration of drug-pressure, but had ED50s consistent with the other three isolates in the group, indicating that the trait of praziquantel-resistance did not necessarily impair biological fitness during laboratory passage. The protocols used here to estimate the praziquantel ED50s of S. mansoni isolates should be useful for establishing and monitoring the drug susceptibility/resistance profiles of parasite isolates freshly obtained from endemic areas, particularly those in which increased usage of the drug is likely to occur.

A study was performed to determine the efficacy of praziquantel (PZQ) against Schistosoma haematobium. Children (n = 592) infected with S. haematobium received either a single treatment with PZQ (40 mg/kg) or two or three treatments with PZQ at three-week intervals after the initial treatment and efficacy was monitored for nine weeks. Cure rates at three-weeks post-treatment were low (< 50%), suggesting either that worms are killed very slowly or, more likely, that eggs continue to be released from tissues after worm death. Interestingly, a single dose of PZQ showed high efficacy (cure rate > 83% and egg reduction rate > 98%) when assessed from six weeks post-treatment onward. There were no significant differences in cure rates or intensity of infection between the three cohorts at any point in the study, despite the different treatment regimens. Since children were in contact with transmission sites during the study period, the results suggest good efficacy of PZQ against all stages of S. haematobium, including the immature worms.

In order to set up the present situation on schistosomiasis in the neighbourhoods around the University of Yaounde I campus, a malacological survey (collection of freshwater snails, their identification and tests on cercarial emergence) was carried out monthly over 12 months in 2 water sources, followed by a parasitological diagnosis of intestinal schistosomiasis in subjects who acknowledge having come into contact with the infested water course. The malacological survey revealed 4 freshwater gastropod species, two (Bulinus globosus and Biomphalaria pfeifferi) of which are intermediate hosts of schistosomes. Biomphalaria pfeifferi specimens from the former quarry pond of Ngoa-Ekelle neighbourhood showed an average infestation rate of 9.7%, and emitted schistosome cercariae throughout the whole period of study. The parasitological diagnosis included 112 (81.2%) out of the 138 individuals identified, including 55 males and 57 females; 27 out of the 112 subjects had S. mansoni eggs in stools, making a prevalence rate of 24.1%. These patients were composed of 21 males and 6 females. The prevalence of S. mansoni is therefore significantly higher in males. The average parasitic load for our sample was 248 eggs/g of stools. It was much higher for males (280 eggs/g stools) than for females (136 eggs/g stools). The differences of prevalences and parasitic loads between sex can be explained in part by the varying activities of interest according to the different groups in the infested watering places.

Isoelectric focusing of glucose-6-phosphate dehydrogenase (G6PD) produced clearly identifiable profiles for S. haematobium and S. intercalatum and their hybrids. To provide a more detailed analysis of the interactions of S. haematobium and S. intercalatum in South West Cameroon over the last 12 years, G6PD analyses were carried out on individual schistosomes collected in Kumba in 1990, Loum in 1990, 1999 and 2000 and Barombi Mbo and Barombi Kotto in 1999. Studies were also carried out on the two parental species S. haematobium Barombi Mbo, S. intercalatum Edea and subsequent generations of hybrids resulting from laboratory crosses of the two parental species. The isoenzyme analysis demonstrated that the 1990 isolate from Kumba, was a recombinant of S. intercalatum × S. haematobium, and that 30% of individual schistosomes collected in 1990 in Loum were also recombinants. The remainder gave data indicative of S. haematobium. In 1999, 12.5% of individuals from Loum showed recombination and 10% in 2000. Results from the most recent parasitological survey in October 2000 showed the persistence of the recombinant population in addition to that of S. haematobium. There was also evidence of recombination having taken place in Barombi Kotto but not Barombi Mbo. This study demonstrates how the situation has changed over the last 12 years, and emphasizes the importance of assessing morphological, biological and molecular data together to gain a true picture of the rapidly evolving situation.

Description de Schistosoma guineensis n. sp. In: Taxonomy, ecology and evolution of metazoan parasites. Tome II. Combes C. & Jourdane J. (eds). Presses Universitaires de Perpignan, 139-146.

In: Taxonomy, ecology and evolution of metazoan parasites. Tome II. Combes C. & Jourdane J. (eds). Presses Universitaires de Perpignan, 319-337.

Two recognized strains of Schistosoma intercalatum, one from the Democratic Republic of Congo (DRC), formerly Zaire, and the other from Cameroon, have been investigated using DNA sequences from 3 mitochondrial genes, cytochrome oxidase subunit 1 (cox1), NADH dehydrogenase subunit 6 (nad6) and the small ribosomal RNA gene (rrnS). In addition, partial DNA sequences from the nuclear large subunit ribosomal RNA gene (lsrDNA) were included within the study. Although partial lsrDNA alone reveals little taxonomic information, phylogenetic analysis of the mitochondrial data demonstrates a clear dichotomy between the 2 purported strains and it is proposed that they should be treated as distinct taxa. The 'original' S. intercalatum now falls relatively basal in the S. haematobium group, while the proposed new species is more derived and sister taxon to S. bovis and S. curassoni.

Despite the extremely wide distribution of both intermediate (snail) and definitive hosts, the species Schistosoma intercalatum has a highly restricted distribution in parts of West Africa (Cameroon, Equatorial Guinea, Gabon, Nigeria, Democratic Republic of Congo and São Tomé). Recent studies showed that the epidemiology of this species is very dynamic, including invasions and extinctions. This article reviews the epidemiology of S. intercalatum in Cameroon, where the species is endangered, and analyses its overall status in Africa. The possible reasons for the limited distribution of S. intercalatum are discussed.

Prevalence and abundance of Schistosoma haematobium and soil-transmitted helminths (STH) were assessed among a total of 1600 pupils (urine, n = 1190; faecal samples, n = 1454) attending five schools in Loum, Littoral Province, Cameroon, with the specific aim of assessing the extent of polyparasitism and the extent to which infections were focused in particular subsets of the study group. Prevalence of S. haematobium was 62.8% with an abundance (arithmetic mean of egg counts) of 54 eggs/10 ml urine. For the STH these were 47.7% and 619 eggs per gram of faeces (EPG) for Trichuris trichiura, 65.5% and 3636 EPG for Ascaris lumbricoides, and 1.4% and <0.1 EPG for hookworms. Most children (90.3%) were infected with at least one of these four species, the largest proportion (34.3%) carrying two species; 27.4% carried three and 1.1% carried concurrently all four species of parasites. The average number of species harboured increased with age, as did the prevalences of S. haematobium and T. trichiura but not that of A. lumbricoides. All STH showed marked differences in prevalence between the five schools but only T. trichiura varied significantly between sexes. Mean abundance of infection varied significantly between age classes, among schools and between the sexes, with females showing heavier mean EPGs for A. lumbricoides and S. haematobium infections in males. A highly significant association was detected between A. lumbricoides and T. trichiura, that was not context-dependent. This was confirmed in quantitative analyses after controlling for differences in abundance between schools, sexes and age classes. A weaker context-dependent association (prevalence data) was detected between S. haematobium and A. lumbricoides (sex- and age-dependent) but quantitative associations between these two species, as well as between S. haematobium and T. trichiura, were not convincing.

Objectives: To analyse the relationships between the frequency of ectopic localizations of Schistosoma haematobium and S. mansoni eggs. Methods: Studies were conducted in 11 villages in north Cameroon, around Bessoum, a village where an epidemic of bloody diarrhoea caused by S. mansoni occurred in 1997. Results: The results revealed infection prevalence rates of 70.5% for S. haematobium and 30.8% for S. mansoni. Interestingly, S. mansoni eggs were found in 14.5% of the urine samples and S. haematobium eggs in 3% of the stool samples. These ectopic eliminations of schistosome eggs resulted from sexual interactions between the two species of schistosomes, and from a spill-over of high infection loads. The clinical study showed that the morbidity was lower in individuals with mixed infections and high loads of S. haematobium than in those with S. mansoni infections only, suggesting a possible lowering effect of S. haematobium infection on S. mansoni morbidity. Discussion: The results obtained in human populations are discussed in relation to the known schistosome interspecific interactions in animal models.

Human helminth infections [intestinal nematode infections such as Ascaris lumbricoides, Trichuris trichiura, and hook-worm, and schistosome infections such as Schistosoma haematobium and S. mansoni] affect more than a quarter of the world's population, with potential consequences for the health and nutritional and educational development of infected individuals. The advent of broad-spectrum anthelminthic drugs that are cheap, safe, and simple to deliver has meant that control has become a viable option for many countries. Because helminth infections patterns are highly heterogeneous, methods to identify priority areas for intervention against intestinal nematode and schistosome will enhance the efficacy of control. This paper describes the use of NOAA-AVHRR data to develop logistic regression models that predict the probability of infection prevalence greater than 50 percent, and thus warrant mass treatment for intestinal nematodes and schistosomes, according to WHO'S criteria. Moreover, by overlaying the resulting risk maps on population surfaces, it is possible to estimate the school-aged population size requiring mass treatment and also provide an estimate of program costs.

Reciprocal crosses (Schistosoma intercalatum male Zaire×S. intercalatum female Cameroon: S. intercalatum female Zaire×S. intercalatum male Cameroon) were produced in 10 mice by exposing each mouse to 60 male cercariae of one isolate and 60 female cercariae of the other isolate, and vice versa. Hybrid generations originating from the two crosses were established. The infectivity of the F1, F2, F3 and F4 hybrid generations were evaluated after exposing snails individually to 5 miracidia. A comparative histological study of snails infected with F2 and F4 hybrid sporocysts from both crosses was made to assess abnormalities in the intramolluscan development of the hybrids. The worm recovery rate and fecundity were measured by comparing the fitness of the mid-parents with that of the hybrids. S. intercalatum Cameroon was compatible with Bulinus forskalii and incompatible with B. globosus whereas S. intercalatum Zaire was compatible with B. globosus and incompatible with B. forskalii. In the case of S. intercalatum male Cameroon×S. intercalatum female Zaire, hybrid miracidia develops in both B. forskalii and B. globosus in F1, F2 and F3 generations. The infection rate was much lower for B. globosus and F2 and F3 generations produced few cercariae (less than 30 cercariae in overall per snail) and F4 miracidia were only infective to B. forskalii again producing few cercariae. At 40 days post-infection the sporocyst contains masses of acidophilic granules originating from the breakup of pycnotic nuclei. Similarly the F1, F2 and F3 miracidia of the reciprocal cross (S. intercalatum male Zaire×S. intercalatum female Cameroon) exhibited a dual infectivity for B. forskalii and B. globosus, but cercarial productivity was low (less than 30 cercariae overall per snail for F2 and F3 generations). Histological studies demonstrated sporocyst degeneration in snails infected with F4 generation. In the definitive host, the F1 generation (both crosses) exhibited hybrid vigour in that the worm return was greater than that of the mid-parent, F2 and F3 generations. No significant difference in fecundity was demonstrated between the parental strains and the F1 and F2 generations, yet egg production of the F3 generation was significantly lower. It is apparent that there is a post-zygotic barrier in the crosses of S. intercalatum Zaire and S. intercalatum Cameroon from the F2 generations onwards, and sterility of the F4 hybrid sporocyst supports the concept of the existence of 2 distinct taxa.

Two treatments with praziquantel (PZQ) 40 mg/kg, 40 d apart, were given to individuals in a recently established (<6 years) Schistosoma mansoni focus in the Senegal River Basin (SRB). Efficacy of treatment was evaluated 4 weeks after each treatment. Among 130 individuals who provided stool samples on days 0, 118 and 153 and were treated on days 85 and 125, 113 (87%) were infected with S. mansoni before treatment. The overall geometric mean faecal egg count of the infected individuals was 478 eggs/g. Four weeks after the first treatment (day 118), the overall cure rate was only 42.5% and the overall reduction in intensity of infection was 70.7%. However, 4 weeks after the second treatment (day 153), the overall cure rate rose to 76.1% and the overall reduction in intensity was 88.1%. The greatest increase in cure rate between the 2 treatments was in those individuals who were initially the most heavily infected (>1000 eggs/g). There was no apparent difference in cure rate between younger (<20 years) and older individuals (>20 years). No evidence for the existence of a PZQ tolerant strain of S. mansoni was found. Two treatments of PZQ 40 mg/kg, 40 d apart, were sufficient to give an adequate cure rate and high reductions in the intensity of infection. As there was insufficient time for reinfection between treatment and follow-up to result in egg production, the low cure rate observed after one treatment was probably the result of a combination of high infection intensity and the maturation of pre-existing prepatent S. mansoni infections.

Prior to 1986, Loum, a small town situated 100 km inland from Douala, was the only place in Cameroon where hybridization between Schistosoma haematobium and S. intercalatum was known to occur. In 1986, Ratard & Greer provided clear evidence of a new focus of S. haematobium–S. intercalatum hybridization in Kinding Ndjabi, a small village located about 200 km north-west of Yaoundé, outside the historical hybrid zone of Loum, with overall infection rates of 19% for S. intercalatum and 12% for S. haematobium, and 37% of the 71 infected persons passing schistosome eggs in both stool and urine. Bulinus forskalii was the only snail found during extensive surveys in and around the village. Thirteen years later, as part of a study programme on the evolution of schistosomiasis in mixed infection foci in Cameroon, a parasitological survey of the total population of Kinding Ndjabi was conducted in December 1999. Of 257 persons registered (aged 1–70 years, mean 22 years), 203 stool and 241 urine samples were collected, giving compliance rates of 79% and 94%, respectively. Only 1 person (0.5%) was excreting terminal-spined eggs typical of S. intercalatum, and 4 (2%) were positive for S. mansoni; egg intensities were 192 eggs/g faeces for the single S. intercalatum case and 72 to 840 eggs/g (mean 348 eggs/g) for S. mansoni. Terminal-spined eggs typical of S. haematobium were found in only 1 (0.4%) of the 241 urine samples, at an intensity of 8 eggs/10 mL. All 6 infected individuals were young, and all were treated with praziquantel at 40 mg/kg bodyweight in a single dose. A malacological survey of 6 transmission sites, all previously known water-contact points, was carried out in October 1999 and February 2000. B. forskalii was the only aquatic snail found and was present in October at 2 of the 6 sites. These results document a marked decline in schistosomiasis transmission in the focus following the installation of a water pump in the village.

Le Bulletin de Liaison et de Documentation de l'OCEAC 34: 19-22.

Schistosoma intercalatum, which causes human rectal schistosomiasis in Africa, still presents a great interest for its imprecise taxonomic status and its puzzling distribution in Africa. Two geographically isolated strains of S. intercalatum are recognized, the Lower Guinea strain and the Congo strain, which differ from each other in a number of morphological, biological and biochemical characteristics. Recent molecular data using RAPD markers indicate high divergence between the two strains, with values of Nei and Li's similarity indice allowing recognition of two genetically distinct taxa: experiments on pre- and post-isolating mechanisms are in progress in order to re-evaluate the taxonomic status of this polytypic species. With regard to its geographical distribution, S. intercalatum is characterized by the existence of two stable endemic areas (localized in Lower Guinea and North East of Democratic Republic of Congo) which correspond to the historical areas of species discovery, and the emergence during the last 15 years of new foci of the Lower Guinea strain outside previously known endemic areas. The absence of local adaptation of the Lower Guinea strain to its intermediate host, supported by experimental studies, may help to facilitate the spread of this strain. Nevertheless, the present restricted distribution of this species remains puzzling, because its potential snail hosts (bulinids) are widely distributed throughout much of Africa. Recent experimental and epidemiological studies suggest that interspecific sexual interactions between human schistosomes could have a role in limiting the distribution of S. intercalatum: the competitive sexual processes acting among human schistosomes show that S. haematobium and S. mansoni are always competitively dominant over S. intercalatum. These epidemiological observations lead the authors to distinguish three kinds of transmission foci for S. intercalatum.

The construction of the Diama dam on the Senegal river, the Manantali dam on the Bafing river, Mali and the ensuing ecological changes have led to a massive outbreak of Schistosoma mansoni in Northern Senegal, associated with high intensity of infections, due to intense transmission, and the creation of new foci of S. haematobium. Data on the vectorial capacity of Biomphalaria pfeifferi from Ndombo, near Richard Toll, Senegal are presented with sympatric and allopatric (Cameroon) S. mansoni. Comparisons are made on infectivity, cercarial production, chronobiology of cercarial emergence and longevity of infected snails. Recent data on the intermediate host specificity of different isolates of S. haematobium from the Lower and Middle Valley of the Senegal river basin (SRB) demonstrate the existence of at least two strains of S. haematobium. The role of Bulinus truncatus in the transmission of S. haematobium in the Lower and Middle Valleys of the SRB is reviewed. Both S. haematobium and S. mansoni are transmitted in the same foci in some areas of the SRB.

Ten mice were individually exposed to 30 male and 30 female cercariae of Schistosoma intercalatum from Cameroon and to 30 male and 30 female cercariae of S. intercalatum from Zaire. Ten weeks later, the nine surviving mice were killed, and a total of 263 adult schistosomes (228 pairs, 7 unpaired males, 28 unpaired females) were perfused. All worms were identified utilising the random amplified polymorphic DNA technique using primer OPG06 which enables the differentiation of the Cameroon and Zaire genotypes. The data demonstrate that there were no significant differences between the number of homospecific pairs observed compared with the expected number under the null hypothesis. Matings occurred in a random manner indicating that mate choice did not exist for the two genotypes of S. intercalatum. Hence there is no prezygotic isolation mechanism which would prevent the interaction of the two genotypes if they were sympatric. However, as they are allopatric, the possibility of the production of unfit hybrids does not arise. Consequently, the reinforcement of a prezygotic isolating mechanism does not play a significant role in the speciation process.

Abstract not available online. Please refer to the published paper for details.

This paper summarizes and concludes in-depth field investigations on suspected resistance of Schistosoma mansoni to praziquantel in northern Senegal. Praziquantel at 40 mg/kg usually cures 70-90% of S. mansoni infections. In an initial trial in an epidemic S. mansoni focus in northern Senegal, only 18% of the cases became parasitologically negative 12 weeks after treatment, although the reduction in mean egg counts was within normal ranges (86%). Among other hypotheses to explain the observed low cure rate in this focus, the possibility of drug resistance or tolerance had to be considered. Subsequent field trials with a shorter follow-up period (6-8 weeks) yielded cure rates of 31-36%. Increasing the dose to 2 x 30 mg/kg did not significantly improve cure rates, whereas treatment with oxamniquine at 20 mg/kg resulted in a normal cure rate of 79%. The efficacy of praziquantel in this focus could be related to age and pre-treatment intensity but not to other host factors, including immune profiles and water contact patterns. Treatment with praziquantel of individuals from the area residing temporarily in an urban region with no transmission, and re-treatment after 3 weeks of non-cured individuals within the area resulted in normal cure rates (78-88%). The application of an epidemiological model taking into account the relation between egg counts and actual worm numbers indicated that the low cure rates in this Senegalese focus could be explained by assuming a 90% worm reduction after treatment with praziquantel; in average endemic situations, such a drug efficacy would result in normal cure rates. Laboratory studies by others on the presence or absence of praziquantel resistance in Senegalese schistosome strains have so far been inconclusive. We conclude that there is no convincing evidence for praziquantel-resistant S. mansoni in Senegal, and that the low cure rates can be attributed to high initial worm loads and intense transmission in this area.

Male and female schistosomes are generally assumed to form stable monogamous pairs for the whole span of their long existence in the mammalian host. Recent evidence from mixed infections has shown that Schistosoma mansoni males can displace S. intercalatum males from their homologous partners, but no information exists about the existence of similar phenomena within a single schistosome species. Here, we determine whether male S. mansoni can displace males of the same species from pre-formed pairs in vivo. The availability of clear-cut genetic markers of drug resistance in schistosomes was exploited to show that hycanthone sensitive S. mansoni males can displace homospecific hycanthone resistant males from pre-formed pairs and vice versa. The frequency of changes is dependent on the magnitude of the excess single males competing with paired worms. The possible mechanics and the biological significance of mate changing are discussed.

The vectorial capacity of Biomphalaria pfeifferi from Ndiangue, Senegal, was investigated with an allopatric isolate of Schistosoma mansoni from Nkolbisson, Cameroon. The snail infection rate after exposure to a single miracidium per snail (MD1) was 56·3%, and 91·6% for snails exposed to 5 miracidia per snail (MD5). The minimum pre-patent period was 21 days. The mean total cercarial production for the MD1 group was 18511 cercariae per snail, and 9757 cercariae for the MD5 group. The maximum production of cercariae for 1 day was 4892 observed in a snail from the MD1 group at day 43 post-infection. The mean longevity of snails was higher in group MD1 (88 days p.i.) than in group MD5 (65 days p.i.). The chronobiological emergence pattern revealed a circadian rhythm with one shedding peak at mid-day. Comparisons are made with the vectorial capacity of the sympatric combination of B. pfeifferi Senegal/S. mansoni Senegal.

The construction of the Diama dam on the Senegal River and the ensuing ecological changes have led to a massive outbreak of Schistosoma mansoni infection in Northern Senegal, associated with very high intensity of infections, due to extremely intense transmission. The vectorial capacity of Biomphalaria pfeifferi from Ndombo, near Richard-Toll was investigated in order to assess the role of the snail–parasite relationship in this particular epidemiological situation. The results revealed an unusually high compatibility between the Senegalese S. mansoni strain and its local snail intermediate host, B. pfeifferi. The snail infection rate after exposure to a single miracidium per snail was 87%. The cercarial production of infected snails was very high, with a mean total production of 50456 cercariae per snail. No significant difference was found in the total cercarial output between snails exposed to 1 miracidium and those exposed to 5 miracidia. The increase in the rate of cercarial output was significantly greater in snails exposed to 5 miracidia, but there was a higher mortality in this group. The chronobiological cercarial production pattern showed a peak around mid-day. The implications of these findings on the epidemiology of schistosomiasis in Northern Senegal are discussed.

Schistosoma haematobium and S. mansoni are two medically important schistosomes, commonly occurring sympatrically in Africa and so potentially able to infect the same human host. Experiments were designed to study the mating behaviour of these two species in mixed infections in hamsters. Analysis of the data obtained showed that both heterospecific and homospecific pairs readily form. No significant difference was seen between the two species in their ability in forming pairs, however, S. mansoni showed a greater homospecific mate preference. Analysis of the data using the Mantel-Haenszel test suggests that mating competition does occur between S. haematobium and S. mansoni, the former being the more dominant species. Both species appeared to be able to change mate, with S. haematobium showing a greater ability in taking S. mansoni females away from S. mansoni males when introduced into a pre-established S. mansoni infection highlighting the competitiveness of S. haematobium. The significance of the results is discussed in relation to the epidemiological consequences occurring in Senegal, and other areas where both species are sympatric.

Abstract not available online. Please refer to the published paper for details.

The members of the family Schistosomatidae, dioecious Digenea, are discussed with regard to their distribution, intermediate and definitive host-parasite relationships. The biological species concept is considered together with the difficulties of its application to Schistosoma spp. and the Digenea. The correlation between pairing of adult schistosomes, physical and sexual development and the maintenance of reproductive potential is emphasised. Development of the female reproductive system does not depend upon species-specific pairing. In some combinations, e.g., Schistosoma haematobium/Schistosoma intercalatum and Schistosoma bovis/Schistosoma curassoni, a specific mate choice system apparently does not exist, whereas it does in other combinations, e.g., Schistosoma mansoni/Schistosoma intercalatum. In mixed infections change of mate may occur and when the opportunity arises heterospecific pairs of worms will change partners to conspecific pairs. Interspecific pairing in adult schistosomes will lead to either hybridisation or parthenogenesis. Yet the majority of schistosomes that inhabit the same definitive host maintain their genetic identity: specific mate recognition, site selection within the host and heterologous immunity have been suggested as isolating mechanisms. Experimental intraspecific crosses have enabled evaluation of the degree to which some populations separated and became reproductively isolated through pre-mating isolating mechanisms, indicative of incipient speciation, e.g., the Lower Guinea and Zaire strains of S. intercalatum. The occurrence and significance of parthenogenesis in schistosomes and other species of Digenea are discussed. The consequences of interspecific mating interactions in schistosomes with regard to parasite epidemiology, interspecific competition and genetic heterogeneity are debated. Geographical isolation and host specificity represent important pre-zygotic isolating mechanisms. It is suggested that site selection within the host and heterologous immunity may both reduce interspecific genetic interchange when digenean parasites utilise the same definitive host.

Abstract not available online. Please refer to the published paper for details.

The F1 and F2 hybrids of Schistosoma haematobium male × S. mattheei female were studied with regard to infectivity to intermediate and definitive hosts, isoenzymes (phosphoglucomutase) of individual male worms, randomly amplified polymorphic DNAs of individual adult worms and scanning electron micrographs of the tubercles of male worms. The infectivity data revealed that the F1 hybrids were infective to both the hamster and the sheep, the sheep being the normal definitive host for S. mattheei. The F2 hybrids were less infective to the sheep, but more so to the sheep than to the hamster. Worm recovery of F1 hybrids was lower than that of the parental strains from both definitive hosts. The worm recovery of F2 hybrids in sheep was significantly lower than that of the parental strains. There was a clear difference in the isoenzyme profiles between S. haematobium and S. mattheei. The RAPD analysis revealed polymorphisms between the parental species and the hybrid generations. Scanning electron microscopy revealed differences in tubercle morphology between the parental species and also between hybrid generations. The potential significance of hybridisation in areas of sympatry between S. haematobium and S. mattheei is discussed.

A survey for Schistosoma intercalatum conducted in Kinshasa, Zaire, in September 1994 revealed a prevalence of 3.6% (n = 167). Three isolates of schistosomes were made by exposing Bulinus wrighti to miracidia hatched from eggs collected from 2 infected children. Characterization of the isolates by biochemical (isoenzymes of phosphoglucomutase), molecular (restriction fragment length polymorphism and randomly amplified polymorphic deoxyribonucleic acid analysis) and morphological (egg measurements) techniques confirmed the existence of an autochthonous transmission focus of S. intercalatum in Kinshasa. The study also provided evidence of the occurrence of natural hybridization between S. intercalatum and S. haematobium. No potential snail host for either species was found in the 2 rivers examined. Apart from Bu. globosus from Zambia and Bu. wrighti, snail infection experiments showed an incompatible relationship between the parasite isolates and snails belonging to the Bu. forskalii group, the Bu. iruncatus/Bu. tropicus complex, and the Bu. africanus group.

The compatibility between Schistosoma intercalatum (Cameroon) and two wild rodents commonly found in Africa. Mastomys huberti (the multimammate mouse) and Arvicanthis niloticus (the Nile rat) was studied to determine their biological capacities to act as hosts for S. intercalatum. In both rodent species the general mean worm recovery was high (33 +/- 0.1% in M. huberti and 33.8 +/- 0.1% in A. niloticus) and worm mortality was very low from 6 to 20 weeks postinfection; parasite maturity was reached. The high number of released eggs as well as the viability and the infectivity of the miracidia to the snail vector showed that M. huberti and A. niloticus are very permissive to S. intercalatum and may act as hosts for the human disease.

Investigations by Van Wijk (1969) provided ample evidence that, before 1968, Schistosoma intercalatum was the only species of schistosome occurring in Loum, a small town situated 100 km inland from Douala, the main port of Cameroon. In a survey of 500 schoolchildren aged between 4 and 15 years, Van Wijk obtained an overall infection rate of 54.2% with S. intercalatum, and no case of urinary schistosomiasis was found. Subsequently, by 1972, some children in one part of the town were found to be passing schistosome eggs in their urine, and these eggs ranged in shape and size from the forms characteristic of S. haematobium to those of S. intercalatum; natural hybridization between the 2 species was shown to be occurring (Wright et al., 1974). It thus appeared that S. haematobium had become established in Loum sometime between 1968 and 1972. In this area, each parasite utilizes a different snail host: S. haematobium develops in Bulinus truncatus and S. intercalatum in B. forskalii. A clear correlation between the distribution of the snail hosts in the river Mbette, the main river which passes through the town, and its tributaries, and the distribution of schistosomes in the human populations was demonstrated by Southgate et al. (1976). By 1973 it was already evident that substantial changes had occurred in the epidemiology of schistosomiasis in Loum over a short time, S. haematobium supplanting S. intercalatum. Comparison of stool and urine examinations in 1968, 1973, 1978 and 1987 confirmed the marked swing from intestinal to urinary schistosomiasis; all the evidence pointed to S. intercalatum being replaced by S. haematobium through introgressive hybridization, possibly associated with an interspecific competitive exclusion mechanism. In order to follow the evolution of schistosomiasis levels in Loum and to reassess the prevalences of intestinal and urinary schistosomiasis, a parasitological survey of schoolchildren was carried out in November 1996 in quarters adjacent to the river Mbette, where high infection prevalences had previously been reported. Four schools were sampled and 426 schoolchildren aged 4–17 years (mean 10 years) were examined. Three of the 4 schools were exhaustively sampled, both stool and urine samples being collected from all the schoolchildren, whereas in the fourth school, where there were more pupils (402), samples were collected from 45% of the children randomly (30 individuals per class). Stool samples were examined by a single thick smear technique using a 43 mg Kato-Katz template, and 10 mL of each urine sample was filtered with Nucleopore filters, the filters being stained with iodine and examined. In addition to the parasitological survey, the Mbette river and its tributaries were searched for snails at 7 selected sites, all known to be water-contact points. Of the 426 pupils examined, 221 (51.9%) were excreting terminal-spined schistosome eggs in their urine, with school prevalences ranging from 47.1% to 55.8% and no significant difference between the sexes. Heavy infections (>50 eggs/10 mL urine) accounted for 21.4% of those examined, and the overall geometric mean intensity among positive samples was 36 eggs/10 mL. No S. intercalatum eggs were recovered from any stool sample. Set against the 1968 baseline, when 271 of 500 children (54%) were stool-positive and none were urine-positive, the 1996 findings document the complete replacement of S. intercalatum by S. haematobium at Loum within less than 30 years.

Previously assumed to be monogamous, the mating system of schistosomes has been the subject of some debate since recent findings have shown that change of mate can occur among these parasites. Here, Louis-Albert Tchuem Tchuente, Vaughan R. Southgate, Claude Combes and Joseph Jourdane review progress made in the understanding of the mating behaviour of schistosomes, and highlight the importance of mating systems in the dynamics of natural transmission of schistosomiasis.

A study on the immune and mating interactions between Schistosoma intercalatum and S. mansoni has been carried out. The immunologically mediated interactions and mating patterns observed between the two species demonstrate that S. mansoni is competitively dominant over S. intercalatum. When S. mansoni females are absent, S. mansoni males are more competitive than S. intercalatum males at pairing with S. intercalatum females. The use of a mathematical model shows how the abundance of S. mansoni worms per host could dramatically affect the mating probability of S. intercalatum females with their homologous males. It appears that the competitive exclusion between these two species of schistosomes may probably be an important factor restricting the distribution of S. intercalatum in Africa.

Previous studies on mating behaviour of Schistosoma intercalatum and S. mansoni, two human schistosomes which may overlap in parts of Africa, have shown that in mixed infections in mice there are no physiological barriers preventing heterospecific pairings. However, when choice is possible, matings occur preferentially between partners of the same species. In this paper, further experimental studies on mating behaviour of the two species were conducted. Sequential infections showed that heterospecific pairs of worms change partners to homospecific pairs when given the opportunity. The change of mate is a progressive process requiring up to, at least 8 weeks, and this phenomenon is due to the male worm seeking the appropriate female. S. mansoni males are better at pairing with females than S. intercalatum males, and they will change partner to pair with homologous females in preference to heterologous females whenever given the opportunity. Moreover, in the absence of S. mansoni female worms, unpaired S. mansoni male worms pull away female S. intercalatum from male S. intercalatum. It appears from this study that S. mansoni males are much more competitive than S. intercalatum males at pairing with females, and this is a disadvantage for S. intercalatum in situations of sympatry.

Among the five species of schistosomes pathogenic to humans, only Schistosoma mansoni, which causes intestinal schistosomiasis, is present in both the Old and the New World, respectively in Africa and South America including some of the Caribbean islands. Some authors believe that the presence of S. mansoni in South America results from a recent introduction in the 16th and 17th centuries from Africa, presumably during the slave trade, and recent phylogenetic molecular studies support this idea. In South America, S. mansoni has been adapted to numerous species of Biomphalaria, principally Biomphalaria glabrata, whose very wide distribution has allowed a firm establishment of the parasite in the tropical zones of this continent and nearby islands. The isolation due to the oceanic barrier and the transfer of the parasite to new species of molluscs facilitate evolution and subsequent diversification of the two populations. Many recent works have shown that S. mansoni populations of the New World differ from the African stock, in morphology, specificity toward snails and rodents, cercariae-shedding chronobiology, and susceptibility to drugs. The application of genetic polymorphic isoenzymatic markers has not apparently revealed significant divergence between the two populations, although those authors were surprised at this result and considered that the sample size and laboratory maintenance may have contributed toward a loss of heterogeneity. Imbert-Establet and Combes (1986) have shown that S. mansoni from Africa (Cameroon) and S. mansoni from the New World (Guadeloupe) hybridize very well under experimental conditions. However, the conditions used by these authors did not determine whether mate preference leads to a prezygotic reproductive isolation between the two populations: only cross-infections without the possibility of mate choice were conducted, the vertebrate host being infected with males of one population and females of the other. Studies have recently demonstrated, in the S. mansoni–Schistosoma intercalatum model, that assortative mating can effectively constitute a reproductive isolating barrier in schistosomes. The finding of molecular genetic markers enabling differentiation between S. mansoni strains allows research on sexual isolating mechanisms between populations of the same species. This paper presents the results of an experimental approach examining the level of reproductive isolation between two populations of S. mansoni, one African (Cameroon) and one South American (Brazil), distinguished by molecular markers (RAPDs). The aim of the work is to test the aptitude of each of the two populations to constitute homologous pairs in experimental situations where the vertebrate host is simultaneously infected with both male and female worms of both parasite populations. African S. mansoni was isolated from a batch of naturally infected Biomphalaria pfeifferi collected in Cameroon, in the Nkolbisson area, in 1993; American S. mansoni, originating from Brazil in the Recife area, was cycled in the laboratory for several years in B. glabrata.

Among which species, in what situations and how, does parthenogenesis occur in the biology of reproduction of schistosomes? Here, Jose Jourdane, Daniele Imbert-Establet and Louis Albert Tchuem Tchuente review the literature on parthenogenesis in schistosomes, and debate the evolutionary aspects of this type of reproduction.

In mixed infections of Schistosoma haematobium and S. mattheei, homospecific and heterospecific pairs are formed, with a preponderance of homospecific pairs indicating the existence of a mate preference system. S. haematobium apparently exhibits a greater specific mate recognition system than does S. mattheei. In sequential infections when mice are exposed to S. mattheei 4 weeks after infection with S. haematobium, S. haematobium males are better at pairing with S. mattheei females than are S. mattheei males. Hence, genetic exchanges between S. haematobium and S. mattheei giving rise to viable hybrids poses the problem of the genetic identity of these species of schistosomes. The most important reproductive isolating mechanisms are definitive host specificity, S. haematobium being primarily a parasite of man, whereas S. mattheei is a parasite of domestic stock and wild ungulates, and the preference for homo-specific pairings in simultaneous infections. In contrast, when S. haematobium is the older infection, S. haematobium males are better than S. mattheei males at pairing with females of either species. Hybridisation is the likely outcome of such interactions. The lack of viability of S. mattheei male X S. haematobium female indicates genetic differences between the two species. Occurrences of natural hybridisation between S. haematobium and S. mattheei may lead to a change in the response of the parasite to chemotherapeutic treatment.

Experimental studies of mating behaviour of Schistosoma intercalatum and Schistosoma mansoni in mixed infections in mice showed that in simultaneous infections, without the possibility of choice of mate, heterologous pairing occurs readily. The paired females reach sexual maturity, are inseminated and lay parthenogenetic eggs. Miracidia originating from the S. mansoni male × S. intercalatum female are non infective to either Biomphalaria glabrata or Bulinus forskalii, whereas those from the reverse cross show a very low infectivity to only B. glabrata. The resulting haploid male cercariae also show a very low infectivity to mice (1.1%) and consequently only a very small number of adult worms develop. It appears from this study, on chromosomal and electrophoretic evidence, that generative (haploid) parthenogenesis occurs in S. mansoni females paired with S. intercalatum males.

In Africa, the two human schistosome parasites, Schistosoma intercalatum and S. mansoni, can be found sympatrically, which poses the problem of the nature of their reproductive isolation. In this paper, experimental studies of mating behaviour in mixed infections in mice were carried out. Simultaneous infections without choice of mate showed an absence of any physiological barriers preventing encounter and mating of the two species on the same host. Whenever choice was possible, mating did not occur in a random way, but preferentially between partners of the same species (there was a significant prevalence of homospecific pairs). S. mansoni exhibited greater specific mate recognition than S. intercalatum. Moreover, in the absence of S. mansoni female worms, S. mansoni male worms were as competitive as S. intercalatum male worms in pairing with S. intercalatum female worms. It appears from this study that the choice of mate is a reproductive isolating factor between the two species.

A study of the compatibility between Schistosoma intercalatum from Cameroon and its potential vectors Bulinus forskalii from Cameroon, Equatorial Guinea, Ivory Coast and Niger has been carried out. As compatibility test, the snail infection test, completed by an histological study, was used. Snail infection experiments showed that all the populations of B. forskalii we tested are very good potential vectors, with infection rates ranging between 76.5 and 93%. The histological study revealed no defense reaction in the snails, which confirms the perfect compatibility of the B. forskalii populations we studied. In an epidemiological perspective, this study confirms the ever present risk of extension of S. intercalatum parasitosis in Africa.