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Schistosomiasis, a neglected tropical disease, is a widespread chronic helminthiasis reported in 78 countries, predominantly those within sub-Saharan Africa, as well as Latin America, Asia, and most recently, even Europe. Species of the causative blood fluke infect not only humans but also animals, and hybrids between previously assumed human-specific and animal-specific schistosomes are being increasingly reported. Existing control programs across Africa focus on humans and rely heavily on mass drug administration of praziquantel, the sole drug available against schistosomiasis. Praziquantel is safe and highly efficacious but could become ineffective if resistance emerges. To reach the revised World Health Organization goal of elimination of schistosomiasis as a public health problem, and interruption of transmission within selected regions, by 2030, new consideration of the role of animal reservoirs in human transmission in general, and whether to also treat livestock with praziquantel in particular, has been raised. However, whilst there are no dedicated control programs targeting animals outside of Asia, there are emerging reports of the use and misuse of praziquantel in livestock across Africa. Therefore, to effectively treat livestock in Africa and to help mitigate against the potential evolution of praziquantel resistance, structured control strategies are required. Here, using a transmission modelling approach, we evaluate the potential effectiveness of a theoretical test-and-treat (TnT) strategy to control bovine schistosomiasis using a currently available point-of-care diagnostic test (developed for human use) to detect circulating cathodic antigen (POC-CCA). We show that implementing TnT at herd-level from 2022 to 2030 could be highly effective in suppressing infection in cattle and even, in lower prevalence settings, reaching nominal ‘elimination’ targets. We highlight the importance of enhancing the specificity of POC-CCA for use in livestock to avoid unnecessary treatments and discuss the outstanding challenges associated with implementing TnT as part of a holistic One Health approach to tackling human and animal schistosomiasis.

Schistosomiasis is a major neglected tropical disease (NTD) affecting both humans and animals. The morbidity and mortality inflicted upon livestock in sub-Saharan Africa has been largely overlooked, in part due to a lack of validated sensitive and specific tests, which do not require specialist training or equipment to deliver and interpret. Inexpensive, non-invasive, and sensitive diagnostic tests for livestock-use would also facilitate both prevalence mapping and appropriate intervention programmes. The aim of this study was to assess the sensitivity and specificity of the currently available point-of-care circulating cathodic antigen test (POC-CCA), designed for Schistosoma mansoni detection in humans, for the detection of intestinal livestock schistosomiasis caused by Schistosoma bovis and Schistosoma curassoni. POC-CCA, together with the circulating anodic antigen (CAA) test, miracidial hatching technique (MHT) and organ and mesentery inspection (for animals from abattoirs only), were applied to samples collected from 195 animals (56 cattle and 139 small ruminants (goats and sheep) from abattoirs and living populations) from Senegal. POC-CCA sensitivity varied by ruminant group and by location/parasite species: sensitivity was greater in Barkedji (cattle: mean 81% (95% credible interval (CrI): 55%-98%); small ruminants: 49% (29%-87%), where livestock were primarily infected by S. curassoni, than in Richard Toll (cattle: 62% (41%-84%); small ruminants: 12% (1%-37%), where S. bovis was the main parasite species. Mean POC-CCA specificity across sites in small ruminants was 91% (77%-99%) with little variation between locations/parasites (Barkedji: 91% (73%-99%); Richard Toll: 88% (65% - 99%). Specificity could not be assessed in cattle owing to the low number of uninfected cattle surveyed. Overall, our results indicate that, whilst the current POC-CCA does represent a potential diagnostic tool for animal schistosomiasis, future work is needed to develop a livestock-specific affordable and field-applicable diagnostic tests to enable determination of the true extent of livestock schistosomiasis.Author summarySchistosomiasis is a debilitating neglected tropical and zoonotic disease, infecting over 230 million people and multiple millions of animals worldwide, most notably amongst the poorest regions and populations. The potential contribution of livestock schistosomiasis to disease transmission in human populations has implications for the design of effective disease management and elimination programmes. However, our understanding of the true prevalence, transmission and impact of animal schistosomiasis is severely limited, in part due to a lack of inexpensive, accessible, sensitive and specific diagnostic tools. As a point-of-care circulating cathodic antigen (POC-CCA) diagnostic test is now in widespread use to assess intestinal schistosomiasis caused by Schistosoma mansoni in humans, we hypothesised that the same test could be used to detect livestock intestinal schistosomiasis caused by Schistosoma bovis and Schistosoma curassoni. The aim of this study was thus to evaluate the sensitivity and specificity of the POC-CCA for the detection of intestinal livestock schistosomiasis in Senegal. POC-CCA sensitivity varied by ruminant group and by location/parasite species, while POC-CCA specificity in small ruminants, at least, did not vary across sites. We conclude that the currently-available POC-CCA does represent a potential diagnostic tool for animal schistosomiasis, but that the factors determining test performance warrant further investigation.

Significance The threat to public health that is presented by zoonotic spillover of pathogens from animal reservoirs is predicted to increase with rapid anthropogenic changes and global trends such as migration and changing land use. Schistosomiasis currently infects more than 220 million people worldwide, and the multihost Schistosoma spp. system within Africa is a key example of where spillover of animal parasites into human populations has enabled the formation of viable hybrid parasite genotypes. Our study demonstrates how zoonotic spillover and complex interactions between pathogen species, such as parasite hybridization, may have implications such as resilience to current disease control strategies and may facilitate the spread of tropical diseases such as schistosomiasis beyond their original geographical boundaries., Zoonotic spillover and hybridization of parasites are major emerging public and veterinary health concerns at the interface of infectious disease biology, evolution, and control. Schistosomiasis is a neglected tropical disease of global importance caused by parasites of the Schistosoma genus, and the Schistosoma spp. system within Africa represents a key example of a system where spillover of animal parasites into human populations has enabled formation of hybrids. Combining model-based approaches and analyses of parasitological, molecular, and epidemiological data from northern Senegal, a region with a high prevalence of schistosome hybrids, we aimed to unravel the transmission dynamics of this complex multihost, multiparasite system. Using Bayesian methods and by estimating the basic reproduction number (R0), we evaluate the frequency of zoonotic spillover of Schistosoma bovis from livestock and the potential for onward transmission of hybrid S. bovis × S. haematobium offspring within human populations. We estimate R0 of hybrid schistosomes to be greater than the critical threshold of one (1.76; 95% CI 1.59 to 1.99), demonstrating the potential for hybridization to facilitate spread and establishment of schistosomiasis beyond its original geographical boundaries. We estimate R0 for S. bovis to be greater than one in cattle (1.43; 95% CI 1.24 to 1.85) but not in other ruminants, confirming cattle as the primary zoonotic reservoir. Through longitudinal simulations, we also show that where S. bovis and S. haematobium are coendemic (in livestock and humans respectively), the relative importance of zoonotic transmission is predicted to increase as the disease in humans nears elimination.

Background: Schistosomiasis is a disease that poses major threats to human and animal health, as well as the economy, especially in sub-Saharan Africa (SSA). Furthermore, its zoonotic nature and the presence of hybrid species complicate efforts to achieve the new World Health Organization’s roadmap for neglected tropical diseases target of elimination. Whilst many studies have evaluated the economic impact of schistosomiasis in humans, only one has been performed to date in livestock in SSA and none in Senegal. The aim of this study was to estimate the financial impact of livestock schistosomiasis in selected regions of Senegal.Methods: Stochastic partial budget models were developed in RiskAmp add-in for Excel for a one-year period to estimate the disease costs on local traditional farmers in twelve villages from the Lac de Guiers and Barkedji regions, Senegal. Disease costs were the sum of disease losses and expenditures and included reduced income due to production losses (e.g. reduced milk yield), expenditures saved (e.g. concentrate feed saved due to disease), additional costs (e.g. testing and treatment, buying replacement animals), and additional income (e.g. selling of diseased animals). The models were parameterised using primary data from cross-sectional surveys and focus group discussions, as well as secondary data from scientific literature and available statistics. Two scenarios were defined based on the most common practices reported: scenario 1 modelled a situation in which the farmers tested and treated their livestock for schistosomiasis; whilst scenario 2 modelled a situation in which there was no tests nor treatment. The model was run with 10,000 iterations for a period of one year; results were expressed in XOF, i.e., the West African CFA franc (1 XOF is equivalent to 0.0014 GBP) with the median and 95% confidence range. Sensitivity analyses were conducted to assess the impact of uncertain variables on the output. Results: For scenario 1, the median disease costs per year and head of cattle, sheep, and goats, respectively, were estimated at XOF -13,408, XOF -27,227 and XOF -27,694. For scenario 2, the disease costs per year and head of cattle, sheep, and goats, respectively, were estimated at XOF -49,296 , XOF -70,072 and XOF -70,281. Sensitivity analyses indicated that the market prices for young and adult, healthy and sick animals had the biggest impact on the disease costs for all species.Conclusions: Our findings suggest that the financial impact of livestock schistosomiasis on traditional subsistence and transhumance farmers in North Senegal is substantial. Consequently, treating livestock schistosomiasis with an effective control strategy has the potential to generate substantial benefits to farmers and their families. Our results can also serve as a baseline for future cost-benefit and cost-effectiveness analyses for potential regional treatment campaigns for schistosomiasis in livestock.

Summary Background Schistosomiasis is a neglected tropical disease of global medical and veterinary importance. As efforts to eliminate schistosomiasis as a public health problem and interrupt transmission gather momentum, the potential zoonotic risk posed by livestock Schistosoma species via viable hybridisation in sub-Saharan Africa have been largely overlooked. We aimed to investigate the prevalence, distribution, and multi-host, multiparasite transmission cycle of Haematobium group schistosomiasis in Senegal, West Africa. Methods In this epidemiological study, we carried out systematic surveys in definitive hosts (humans, cattle, sheep, and goats) and snail intermediate hosts, in 2016–18, in two areas of Northern Senegal: Richard Toll and Lac de Guiers, where transmission is perennial; and Barkedji and Linguere, where transmission is seasonal. The occurrence and distribution of Schistosoma species and hybrids were assessed by molecular analyses of parasitological specimens obtained from the different hosts. Children in the study villages aged 5–17 years and enrolled in school were selected from school registers. Adults (aged 18–78 years) were self-selecting volunteers. Livestock from the study villages in both areas were also randomly sampled, as were post-mortem samples from local abattoirs. Additionally, five malacological surveys of snail intermediate hosts were carried out at each site in open water sources used by the communities and their animals. Findings In May to August, 2016, we surveyed 375 children and 20 adults from Richard Toll and Lac de Guiers, and 201 children and 107 adults from Barkedji and Linguere; in October, 2017, to January, 2018, we surveyed 386 children and 88 adults from Richard Toll and Lac de Guiers, and 323 children and 85 adults from Barkedji and Linguere. In Richard Toll and Lac de Guiers the prevalence of urogenital schistosomiasis in children was estimated to be 87% (95% CI 80–95) in 2016 and 88% (82–95) in 2017–18. An estimated 63% (in 2016) and 72% (in 2017–18) of infected children were shedding Schistosoma haematobium–Schistosoma bovis hybrids. In adults in Richard Toll and Lac de Guiers, the prevalence of urogenital schistosomiasis was estimated to be 79% (52–97) in 2016 and 41% (30–54) in 2017–18, with 88% of infected samples containing S haematobium–S bovis hybrids. In Barkedji and Linguere the prevalence of urogenital schistosomiasis in children was estimated to be 30% (23–38) in 2016 and 42% (35–49) in 2017–18, with the proportion of infected children found to be shedding S haematobium–S bovis hybrid miracidia much lower than in Richard Toll and Lac de Guiers (11% in 2016 and 9% in 2017–18). In adults in Barkedji and Linguere, the prevalence of urogenital schistosomiasis was estimated to be 26% (17–36) in 2016 and 47% (34–60) in 2017–18, with 10% of infected samples containing S haematobium–S bovis hybrids. The prevalence of S bovis in the sympatric cattle population of Richard Toll and the Lac de Guiers was 92% (80–99), with S bovis also found in sheep (estimated prevalence 14% [5–31]) and goats (15% [5–33]). In Barkedji and Linguere the main schistosome species in livestock was Schistosoma curassoni, with an estimated prevalence of 73% (48–93) in sheep, 84% (61–98) in goats and 8% (2–24) in cattle. S haematobium–S bovis hybrids were not found in livestock. In Richard Toll and Lac de Guiers 35% of infected Bulinus spp snail intermediate hosts were found to be shedding S haematobium–S bovis hybrids (68% shedding S haematobium; 17% shedding S bovis); however, no snails were found to be shedding S haematobium hybrids in Barkedji and Linguere (29% shedding S haematobium; 71% shedding S curassoni). Interpretation Our findings suggest that hybrids originate in humans via zoonotic spillover from livestock populations, where schistosomiasis is co-endemic. Introgressive hybridisation, evolving host ranges, and wider ecosystem contexts could affect the transmission dynamics of schistosomiasis and other pathogens, demonstrating the need to consider control measures within a One Health framework. Funding Zoonoses and Emerging Livestock Systems programme (UK Biotechnology and Biological Sciences Research Council, UK Department for International Development, UK Economic and Social Research Council, UK Medical Research Council, UK Natural Environment Research Council, and UK Defence Science and Technology Laboratory).

In West Africa, Schistosoma spp. are capable of infecting multiple definitive hosts, a lifecycle feature that may complicate schistosomiasis control. We characterized the evolutionary relationships among multiple Schistosoma mansoni isolates collected from snails (intermediate hosts), humans (definitive hosts), and rodents (definitive hosts) in Senegal. On a local scale, diagnosis of S. mansoni infection ranged 3.8%-44.8% in school-aged children, 1.7%-52.6% in Mastomys huberti mice, and 1.8%-7.1% in Biomphalaria pfeifferi snails. Our phylogenetic framework confirmed the presence of multiple S. mansoni lineages that could infect both humans and rodents; divergence times of these lineages varied (0.13-0.02 million years ago). We propose that extensive movement of persons across West Africa might have contributed to the establishment of these various multihost S. mansoni clades. High S. mansoni prevalence in rodents at transmission sites frequented by humans further highlights the implications that alternative hosts could have on future public health interventions.

This study was conducted in northern Senegal, covering the regions of Saint-Louis, Louga and Matam, from June 2016 to December 2016. Surveys were carried out at all farms in this area where fish, shrimp, and molluscs farming or grow-out activities are conducted. The sampling method used is the survey determined by respondents which is a variation of snowball sampling. This method allowed us to administer a questionnaire to the fiftynine farms in activity in northern Senegal. The overall objective of this paper is to contribute to the improvement of knowledge on aquaculture biosecurity in the study areas through the application of biosecurity measures. This study highlighted the interconnections between the different farms, identified biosecurity measures for infrastructure, livestock and food, and assessed the different biosecurity measures applied to staff. The results revealed that biosecurity measures are poorly implemented. 74.6% of the people surveyed are also unaware of the mechanisms by which aquatic animal diseases appear and spread out, while 86.4% of them have no knowledge of biosecurity in aquaculture. Our recommendations focus on the need to encourage aquaculture professionals to apply biosecurity measures at all production stages. There is also the need for training or capacity building for aquaculture farmers on biosecurity measures.

The complex multi-host disease dynamics of schistosomiasis and Schistosoma spp., including the emergence of zoonotic parasite hybrids, remain largely unexplored in West Africa. We elucidated the role of wild small mammals as reservoir for zoonotic Schistosoma species and hybrids in endemic areas of Senegal. We identified Schistosoma mansoni, Schistosoma bovis, and a Schistosoma haematobium/S. bovis hybrid, with local prevalence in wild rodents ranging from 1.9% to 28.6%. Our findings indicate that rodents may be an important local reservoir for zoonotic schistosomiasis in endemic areas of West Africa, amplifying transmission to humans and acting as natural definitive hosts of schistosome hybrids.

BackgroundSchistosomiasis and food-borne trematodiases are not only of major public health concern, but can also have profound implications for livestock production and wildlife conservation. The zoonotic, multi-host nature of many digenean trematodes is a significant challenge for disease control programmes in endemic areas. However, our understanding of the epidemiological role that animal reservoirs, particularly wild hosts, may play in the transmission of zoonotic trematodiases suffers a dearth of information, with few, if any, standardised, reliable diagnostic tests available. We combined qualitative and quantitative data derived from post-mortem examinations, coprological analyses using the Mini-FLOTAC technique, and molecular tools to assess parasite community composition and the validity of non-invasive methods to detect trematode infections in 89 wild Hubert’s multimammate mice (Mastomys huberti) from northern Senegal.ResultsParasites isolated at post-mortem examination were identified asPlagiorchissp.,Anchitremasp.,Echinostoma caproni,Schistosoma mansoni, and a hybrid betweenSchistosoma haematobiumandSchistosoma bovis. The reports ofE. caproniandAnchitremasp. represent the first molecularly confirmed identifications for these trematodes in definitive hosts of sub-Saharan Africa. Comparison of prevalence estimates derived from parasitological analysis at post-mortem examination and Mini-FLOTAC analysis showed non-significant differences indicating comparable results between the two techniques (P = 1.00 forS. mansoni;P = 0.85 forE. caproni;P = 0.83 forPlagiorchissp.). A Bayesian model, applied to estimate the sensitivities of the two tests for the diagnosis ofSchistosomainfections, indicated similar median posterior probabilities of 83.1% for Mini-FLOTAC technique and 82.9% for post-mortem examination (95% Bayesian credible intervals of 64.0–94.6% and 63.7–94.7%, respectively).ConclusionsOur results showed that the Mini-FLOTAC could be applied as an alternative diagnostic technique for the detection of the zoonoticS. mansoniand other trematodes in rodent reservoirs. The implementation of non-invasive diagnostics in wildlife would offer numerous advantages over lethal sampling methodologies, with potential impact on control strategies of zoonotic helminthiases in endemic areas of sub-Saharan Africa and on fostering a framework of animal use reduction in scientific practice.

Trematodes of the genus Plagiorchis have a wide geographical distribution and can exploit a variety of hosts. The occurrence and zoonotic potential of Plagiorchis spp. have been characterised across several countries in Asia; in contrast, information on Plagiorchis parasites in Africa remains anecdotal. We isolated a previously undescribed Plagiorchis species from the biliary tract and small intestine of 201 out of 427 small mammals collected in the region of Lake Guiers, Senegal, with local prevalence ranging from 38.6% to 77.0%. Conversely, Plagiorchis isolates were not observed in the 244 small mammals sampled in and around the town of Richard Toll, Senegal. Molecular phylogenetics of the internal transcribed spacer region, nuclear ribosomal DNA, and of the cytochrome c oxidase subunit 1 gene, mitochondrial DNA, supported the monophyly and multi-host spectrum of this newly discovered West African Plagiorchis species. Sequencing of individual cercariae shed by Radix natalensis (Gastropoda: Lymnaeidae) suggested that these freshwater snails may act as suitable first intermediate hosts. Phylogenetic analysis yielded a highly resolved topology indicating two different clades, one composed by Plagiorchis spp. infecting rodents, insectivores, and birds, while the other included parasites of bats. Our findings showed the low host specificity and high prevalence of the isolated Plagiorchis sp. in the Lake Guiers region, with Hubert's multimammate mice (Mastomys huberti) appearing to play a primary role in the epidemiology of this parasite. The results raise concern about the zoonotic potential of Plagiorchis sp. in local communities of the Lake Guiers region, and highlight food-borne trematodiases and their link to land-use change as a neglected public health issue in regions of West Africa., Graphical abstract Image 1, Highlights • Monophyletic, previously undescribed Plagiorchis lineage in African small mammals. • High local prevalence ranging from 38.6% to 77.0% in the examined hosts. • Identification of the gastropod Radix natalensis as first intermediate host. • Potential role of Plagiorchis sp. as emerging zoonotic pathogen in northern Senegal.

West Nile fever is an arthropod-borne viral disease of public health importance transmitted by mosquitoes from the genus Culex. Birds are the main hosts/reservoirs of West Nile virus (WNV; Flaviviridae, Flavivirus) and ensure its spread worldwide toward migration. The WNV is continuously spreading across the world with significant health and economic impact in human and animals, especially in newly infected areas where many human and animal losses are reported. However, in most of the African countries where the disease is endemic, no or few human or animal cases are reported in contrast with the high prevalence of the disease and the recurrent circulation of the virus. These gaps could be related to the fact that clinical signs are similar to those of dominant pathologies in human or equine encephalitis in animal health allowing to a misdiagnosis.

Hydatigera (Cestoda: Taeniidae) is a recently resurrected genus including species seldom investigated in sub-Saharan Africa. We surveyed wild small mammal populations in the areas of Richard Toll and Lake Guiers, Senegal, with the objective to evaluate their potential role as intermediate hosts of larval taeniid stages (i.e. metacestodes). Based on genetic sequences of a segment of the mitochondrial DNA gene cytochrome c oxidase subunit 1 (COI), we identified Hydatigera parva metacestodes in 19 out of 172 (11.0%) Hubert's multimammate mice (Mastomys huberti) and one out of six (16.7%) gerbils (Taterillus sp.) and Hydatigera taeniaeformis sensu stricto metacestodes in one out of 215 (0.5%) Nile rats (Arvicanthis niloticus). This study reports epidemiological and molecular information on H. parva and H. taeniaeformis in West African rodents, further supporting the phylogeographic hypothesis on the African origin of H. parva. Our findings may indicate significant trophic interactions contributing to the local transmission of Hydatigera spp. and other parasites with similar life-cycle mechanisms. We therefore propose that further field investigations of rodent population dynamics and rodent-borne infectious organisms are necessary to improve our understanding of host–parasite associations driving the transmission risks of rodent parasites in West Africa.