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Schistosomiasis is one of the most important parasitic diseases in tropical and subtropical areas. Its prevalence is associated with the distribution of freshwater snails, which are their intermediate hosts. Thus, control of freshwater snails is the solution to reduce the transmission of this disease. This will be achieved by understanding the relationship between the snails and their habitats including natural enemies and associated aquatic plants as well as the factors affecting their distribution. In this study, Maximum Entropy model (MaxEnt) was used for mapping and predicting the possible geographic distribution of Bulinus truncatus snail (the intermediate host of Schistosoma haematobium), Odonata nymph (predatory aquatic insect), and Ceratophyllum demersum (the associated aquatic plant) in Egypt based on topographic and climatic factors. The models of the investigated species were evaluated using the area under receiver operating characteristic curve. The results showed that the potential risk areas were along the banks of the Nile River and its irrigation canals. In addition, the MaxEnt models revealed some similarities in the distribution pattern of the vector, the predator, and the aquatic plant. It is obvious that the predictive distribution range of B. truncatus was affected by altitude, precipitation seasonality, isothermality, and mean temperature of warmest quarter. The presence of B. truncatus decreases with the increase of altitude and precipitation seasonality values. It could be concluded that the MaxEnt model could help introducing a predictive risk map for Schistosoma haematobium prevalence and performing better management strategies for schistosomiasis.

Understanding of the larval trematode infections in snail intermediate hosts is essential in designing appropriate control measures. The current study was designed to determine larval trematode infection and seasonal variations in freshwater intermediate host snails Iringa and Arumeru Districts where trematode infections in cattle are endemic. A repeated cross-sectional study was adopted whereby Snails were collected three times a year (dry, early wet and mid wet). The selection of water bodies for sampling was based on random sampling and snails were collected by scooping method. The collected snails were identified based on the published morphological keys. A total of 2,016 snails were collected and 134 (6.6%) were found to be infected with trematode larvae. Six species of snails were identified that were Radix natalensis, Bulinus africanus group snails, Bulinus tropicus group snails, Bulinus forskalli group snails, Biomphalaria pfeifferi and Ceratophallous natalensis. Five morphologically different types of cercariae were identified that included gymnocephalous, amphistomes, mammalian Schistosoma, avian Schistosoma and Xiphidiocercariae. The findings on overall seasonal snail infection rates indicated low rate during the wet season while peak of infections were in the dry and early wet seasons. It is concluded that domesticated ruminants in the study areas are at high risk of getting infected with the trematodes (Fasciola and amphistomes) during dry and early wet seasons. Therefore, deworming of domesticated ruminants with an effective flukicide is recommended at the end of the wet season and followed by a treatment in mid dry season and the last treatment in early wet season.

Background Gastropod snails remain strongly understudied, despite their important role in transmitting parasitic diseases. Knowledge of their distribution and population dynamics increases our understanding of the processes driving disease transmission. We report the first study to use high-throughput sequencing (HTS) to elucidate the population genetic structure of the hermaphroditic snail Bulinus truncatus (Gastropoda, Heterobranchia) on a regional (17–150 km) and inter-regional (1000–5400 km) scale. This snail species acts as an intermediate host of Schistosoma haematobium and Schistosoma bovis, which cause human and animal schistosomiasis respectively. Methods Bulinus truncatus snails were collected in Senegal, Cameroon, Egypt and France and identified through DNA barcoding. A single-end genotyping-by-sequencing (GBS) library, comprising 87 snail specimens from the respective countries, was built and sequenced on an Illumina HiSeq 2000 platform. Reads were mapped against S. bovis and S. haematobium reference genomes to identify schistosome infections, and single nucleotide polymorphisms (SNPs) were scored using the Stacks pipeline. These SNPs were used to estimate genetic diversity, assess population structure and construct phylogenetic trees of B. truncatus. Results A total of 10,750 SNPs were scored and used in downstream analyses. The phylogenetic analysis identified five clades, each consisting of snails from a single country but with two distinct clades within Senegal. Genetic diversity was low in all populations, reflecting high selfing rates, but varied between locations due to habitat variability. Significant genetic differentiation and isolation by distance patterns were observed at both spatial scales, indicating that gene flow is not strong enough to counteract the effects of population bottlenecks, high selfing rates and genetic drift. Remarkably, the population genetic differentiation on a regional scale (i.e. within Senegal) was as large as that between populations on an inter-regional scale. The blind GBS technique was able to pick up parasite DNA in snail tissue, demonstrating the potential of HTS techniques to further elucidate the role of snail species in parasite transmission. Conclusions HTS techniques offer a valuable toolbox to further investigate the population genetic patterns of intermediate schistosome host snails and the role of snail species in parasite transmission. Graphical Abstract

Background: Schistosomiasis, due to S. mansoni, is prevalent in Rwanda. However, there is a paucity of information related to the abundance, species, distribution, and infectivity of Schistosoma intermediate host snails. Methods: Snails were collected from 71 sites, including lakeshores and wetlands. Snails obtained were morphologically identified, and cercariae were shed using standard procedures. Cercariae were molecularly characterized using PCR. GPS coordinates were used to generate geospatial maps of snail distribution that were overlaid with geospatial distribution of schistosomiasis among pre-school children in the same areas. Results: Overall, 3653 snails were morphologically classified as Bulinus spp. and 1449 as Biomphalaria spp. A total of 306 snails shed cercariae, 130 of which were confirmed as S. mansoni cercaria by PCR. There was no significant difference in the proportion of S. mansoni cercariae in wetlands compared to lakeshores. Conclusion: Rwandan water bodies harbor an important number of snails that shed S. mansoni cercariae. Furthermore, a strong spatial correlation was observed between the distribution of schistosomiasis in children and the spatial distribution of snail infectivity with S. mansoni. The presence of Bulinus spp. Suggests a potential risk of S. haematobium, although molecular analysis did not show any current transmission of this parasite.

Freshwater snails act as intermediate hosts (IH) for schistosomiasis, a tropical disease affecting over 200 million people worldwide. Despite their medical importance, an extensive understanding of IH snail ecology remains absent. Especially data on the tolerance limits to different abiotic factors are fragmented and incomplete. Consequently, the construction of accurate species distribution models to identify snail habitats and guide targeted snail control efforts remains difficult. Here, we compiled a summary on the tolerance limits to abiotic factors of African IH snails of human schistosomiasis. A systematic search on Web of Science, PubMed, and Embase identified 45 relevant studies. Synthesis of these studies indicates that research efforts differ greatly between IH snail species, life stages, and abiotic factors. The importance of each abiotic factor in determining snail presence and abundance is discussed. Furthermore, attention was drawn to knowledge gaps and the lack of standardised experimental designs, which impedes comparisons between studies. This in turn prevents us from making firm conclusions and calls for best practices adopted by all malacologists. In doing so, IH snail ecological data could serve as a basis to assess schistosomiasis risk and guide snail control efforts in order to support schistosomiasis control. ispartof: Hydrobiologia vol:848 issue:8 pages:1773-1793 status: Published online

The knowledge about the population dynamics of freshwater snail intermediate host and their roles in disease transmission is little known in Bayelsa State. This study investigated the species composition of fresh water snail intermediate host in Amassoma community and the Niger Delta University Campuses during August 2019-October 2019 across five locations (Main campus Hostel, E.T.F Building, Ogboebi-Ama, Efeke-Ama, Ogbopina). Snails were collected from the water bodies with the aid of a scooping net and hand picking. The morphological identification of the snail intermediate host followed standard procedures. From the result, five hundred and seventy-one freshwater snails belonging to four genera and five species were recorded. The presence of Lymnae and Bulinus in the locations highlights foci for fascioliasis and schistosomiasis. The presence of Melanoides spp. is novel in Bayelsa State. The public health implications of these snails have called for timely control intervention.

Reports of snails’ resistance to niclosamide appeared recently and finding new molluscicides becomes necessary. We investigated the molluscicidal effects of Cucurbita maxima seed extracts on Biomph...

Aim: Praziquantel-based chemotherapy is generally effective in the control of morbidity, decline in the prevalence and intensity of Schistosoma mansoni infections. Nevertheless, the potential emergence of praziquantel resistance in S. mansoni posses danger in the elimination of this neglected tropical disease in Africa. Therefore, this study was designed to evaluate the in-vivo efficacy of Praziquantel and Artemisinin using mice infected with S. Mansoni cercariae. Methods: Infected mice with S. mansoni were treated with different doses of Artemisinin and Praziquantel from day 42 post infection to assess its efficacy on adult worms and eggs. A 2-day Protocol: artemisinin 400 mg/kg with Praziquantel of 500 mg/kg daily, 4-day protocol: artemisinin 200 mg/kg with praziquantel of 250 mg/kg daily, 6-day protocol: artemisinin 100 mg/kg with praziquantel of 125 mg/kg daily were used. A value of p

Background: Schistosomiasis is a public health problem of social and economic importance in thedeveloping world. Schistosomiasis haematobium is still endemic in many foci along the Nile valley,especially in El Fayoum and Beni-Suef governorates. Chemotherapy and snail eradication are the mostimportant control measures with few studies that dealt with its snail intermediate host, Bulinus truncatus.Because of drug resistance and recurrence of exposure to infection, snail control becomes a better methodfor control, keeping in mind that chemical molluscicides may have toxic effects on non-target organisms.Objectives: The aim of the study is to search for biologically derived molluscicides such as plant extracts,that are less expensive, available, biodegradable, non-toxic and easily applicable than synthetic ones.Material and Methods: The effect of oil extracts of three natural plants; Nigella sativa, Pelargoniumgraveolens and Azadirachta indica were investigated as molluscicidal agents against B. truncatus snail.Histopathological examination of the soft tissue of the snail was performed after its removal from the shelland its staining with hematoxylin and eosin (HE). Effect of the three plants on miracidia and cercariae ofS. haematobium was also evaluated.Results: The potent molluscicidal effect was demonstrated by disturbance of normal histology andpresence of vacuolated tissues evident by microscopical examination of the dead snails after HE staining.A schistosomicidal effect was also recorded against aquatic stages of the parasite, demonstrated byreduction in the movement of the miracidia, followed by their sinking down together with the cercariae.N. sativa showed the most potent molluscicidal, miracidicidal, as well as cercaricidal activities, followed byP. graveolens, while A. indica had the least effect.Conclusion: These findings recommend the use of the studied plant extracts as safe and effective agentsin the control of S. haematobium in Egypt.

Only a fraction of the Biomphalaria and Bulinus snail community shows patent infection with schistosomes despite continuous exposure to the parasite, indicating that a substantial proportion of snails may resist infection. Accordingly, exterminating the schistosome intermediate snail hosts in transmission foci in habitats that may extend to kilometres is cost-prohibitive and damaging to the ecological equilibrium and quality of water and may be superfluous. It may be more cost effective with risk less ecological damage to focus on discovering the parameters governing snail susceptibility and resistance to schistosome infection. Therefore, laboratory bred Biomphalaria alexandrina and Bulinus truncatus snails were exposed to miracidia of laboratory-maintained Schistosoma mansoni and S. haematobium, respectively. Snails were examined for presence or lack of infection association with soft tissue and hemolymph content of proteins, cholesterol, and triglycerides, evaluated using standard biochemical techniques and palmitic, oleic, linoleic, and arachidonic acid, assayed by ultraperformance liquid chromatography-tandem mass spectrometry. Successful schistosome infection of B. alexandrina and B. truncatus consistently and reproducibly correlated with snails showing highly significant (up toP<0.0001) decrease in soft tissue and hemolymph content of the monounsaturated fatty acid, oleic acid, and the polyunsaturated fatty acids, linoleic, and arachidonic acids as compared to naïve snails. Snails that resisted twice infection had soft tissue content of oleic, linoleic, and arachidonic acid similar to naïve counterparts. High levels of soft tissue and hemolymph oleic, linoleic, and arachidonic acid content appear to interfere with schistosome development in snails. Diet manipulation directed to eliciting excessive increase of polyunsaturated fatty acids in snails may protect them from infection and interrupt disease transmission in a simple and effective manner.

Aims: This research is essentially on the Molluscicidal assessment of Aqueous extract of Moringa oleifera Lam seed on Bulinus Snail for the control of Schistosomiasis. Study Design: This is a controlled study where a total of 810 Bulinus snails were collected from three different streams with each stream representing a community from each of the three senatorial zones of Anambra state where schistosomiasis was endemic. Aqueous extract of Moringa oleifera (Lam) seed at different concentrations were used on the Bulinus snails to determine their molluscidal properties. Place and Duration of Study: Two hundred and Seventy (270) Bulinus snails were collected from streams representing each of the three senatorial zones of Anambra state viz; Obutu Lake, Omogho town, Orumba North Local Government Area (Anambra South), Agulu Lake, Agulu town, Aniocha Local Government Area (Anambra Central) and Omambra River, Omor town, Ayamelum Local Government Area (Anambra North) This research was carried out between November 2018 to April 2019. Methodology: Aqueous dilutions of the grinded Moringa oleifera (Lam) seed were exposed to the Bulinus snails from the various streams for 24 hours, after which the snails were removed from the experimental test solution and washed thoroughly with dechlorinated tap water and transferred to containers with fresh dechlorinated tap water for another 24 hours of recovery. The snails were incubated at 28 ± 5°C and fed with lettuce leaves. Results: Aqueous Moringa oleifera Lam seed extract was toxic to Bulinus adult snails in a dose dependent manner and the total Lethal Concentration (LC50 and LC90) values determined after 24 hours exposure from the whole streams were 468 ppm and 813 ppm respectively. Conclusion: Aqueous seed extract of Moringa oleifera Lam was toxic to Bulinus snail even at low concentrations.

Background Bulinus globosus, the main intermediate snail host of Schistosoma haematobium. The increased contacts between Africa and China could even lead to large-scale dissemination of B. globosus in China. Temperature is the key factor affecting fresh-water snail transmission. This study predicted potential risk of colonization of B. globosus in the mainland of China under climate change. Methods We investigated minimum and maximum temperatures for B. globosus eggs, juveniles and adult snails kept under laboratory conditions to find the most suitable range by pinpointing the median effective temperatures (ET50). We also assessed the influence of temperature on spawning and estimated the accumulated temperature (AT). The average air temperatures between 1955 and 2019 in January and July, the coldest and hottest months in China, respectively, were collected from national meteorological monitoring stations and investigated in a geographic information system (GIS) using empirical Bayesian Kriging to evaluate the theoretical possibility for distribution of B. globosus in southern China based on temperature. Results The effective minimum temperature (ET50min) for eggs, juveniles, adult snails and spawning were 8.5, 7.0, 7.0, 14.9 °C, respectively, with the corresponding maximum values (ET50max) of 36.6, 40.5, 40.2 and 38.1 °C. The AT was calculated at 712.1 ± 64.9 °C·d. In 1955, the potential B. globosus distribution would have had a northern boundary stretching from the coastal areas of Guangdong Province and Guangxi Autonomous Region to southern Yunnan Province. Since then, this line has gradually moved northward. Conclusions Annual regeneration of B. globosus can be supported by the current climate conditions in the mainland of China, and a gradual expansion trend from south to north is shown in the study from 2015 to 2019. Thus, there is a potential risk of colonization of B. globosus in the mainland of China under climate change. Graphical Abstract

Schistosome parasites infect more than 200 million people annually, mostly in sub-Saharan Africa, where people may be co-infected with more than one species of the parasite. Infection risk for any single species is determined, in part, by the distribution of its obligate intermediate host snail. As the World Health Organization reprioritizes snail control to reduce the global burden of schistosomiasis, there is renewed importance in knowing when and where to target those efforts, which could vary by schistosome species. This study estimates factors associated with schistosomiasis risk in 16 villages located in the Senegal River Basin, a region hyperendemic for Schistosoma haematobium and S. mansoni. We first analyzed the spatial distributions of the two schistosomes’ intermediate host snails (Bulinus spp. and Biomphalaria pfeifferi, respectively) at village water access sites. Then, we separately evaluated the relationships between human S. haematobium and S. mansoni infections and (i) the area of remotely-sensed snail habitat across spatial extents ranging from 1 to 120 m from shorelines, and (ii) water access site size and shape characteristics. We compared the influence of snail habitat across spatial extents because, while snail sampling is traditionally done near shorelines, we hypothesized that snails further from shore also contribute to infection risk. We found that, controlling for demographic variables, human risk for S. haematobium infection was positively correlated with snail habitat when snail habitat was measured over a much greater radius from shore (45 m to 120 m) than usual. S. haematobium risk was also associated with large, open water access sites. However, S. mansoni infection risk was associated with small, sheltered water access sites, and was not positively correlated with snail habitat at any spatial sampling radius. Our findings highlight the need to consider different ecological and environmental factors driving the transmission of each schistosome species in co-endemic landscapes., Author summary Schistosome parasites infect more than 200 million people worldwide, mainly in sub-Saharan Africa, where many people are at-risk for infection by multiple schistosome species simultaneously. To reduce the global burden of schistosomiasis, control of the parasites’ intermediate host–specific species of freshwater snails–has been elevated in priority to complement mass drug administration campaigns in endemic areas. To maximize the efficacy and efficiency of snail control efforts, a better understanding of where to target intermediate host snails is badly needed. This includes a better understanding of the spatial scale at which snails in the environment contribute to human infection risk, and, in co-endemic settings, how ecological determinants of infection risk vary by schistosome species. We used quantitative snail sampling and remotely-sensed data at 16 villages in the Senegal River Basin to compare and contrast ecological correlates and spatial scales of infection risk from freshwater snails that transmit Schistosoma haematobium versus S. mansoni. We found that infection risk for S. haematobium was associated with snail habitat at a larger spatial radius than is typically considered for schistosomiasis monitoring and control, whereas infection risk for S. mansoni was not positively correlated with snail habitat at any spatial sampling radius, but was associated with small water access sites enclosed by emergent vegetation. Our findings highlight the need to consider the different ecological and environmental factors driving the transmission of each schistosome species in co-endemic landscapes.

Among the snail genera most responsible for vectoring human-infecting schistosomes, Bulinus, Biomphalaria, and Oncomelania, the former is in many respects the most important. Bulinid snails host the most common human blood fluke, Schistosoma haematobium, responsible for approximately two-thirds of the estimated 237 million cases of schistosomiasis. They also support transmission of schistosomes to millions of domestic and wild animals. Nonetheless, our basic knowledge of the 37 Bulinus species remains incomplete, especially with respect to genome information, even including mitogenome sequences. We determined complete mitogenome sequences for Bulinus truncatus, B. nasutus, and B. ugandae, and three representatives of B. globosus from eastern, central, and western Kenya. A difference of the location of tRNA-Asp was found between mitogenomes from the three species of the Bulinus africanus group and B. truncatus. Phylogenetic analysis using partial cox1 sequences suggests that B. globosus is a complex comprised of multiple species. We also highlight the status of B. ugandae as a distinct species with unusual interactions with the S. haematobium group parasites deserving of additional investigation. We provide sequence data for potential development of genetic markers for specific or intraspecific Bulinus studies, help elucidate the relationships among Bulinus species, and suggest ways in which mitogenomes may help understand the complex interactions between Schistosoma and Bulinus snails and their relatives.

(1) Background: Schistosomiasis remains a public health issue in Cameroon. Snail control using Niclosamide can prevent schistosome transmission. It is safe to determine lethal concentrations for the population. This study aimed at assessing the toxicity of Niclosamide on different developmental stages of snail populations; (2) Methods: Snails were collected, identified, and reared in the laboratory. Egg masses and adult snails were exposed to Niclosamide, at increasing concentrations (0.06, 0.125, 0.25, 0.5, 1 mg/L for egg embryos and 0.06, 0.08, 0.1, 0.12, 0.14, 0.16, 0.18, 0.2 mg/L for adults). After 24 h exposure, egg masses and snails were removed from Niclosamide solutions, washed with source water and observed; (3) Results: Snail susceptibility was species and population dependent. For egg embryos, Biomphalaria pfeifferi was the most susceptible (LC50: 0.1; LC95: 6.3 mg/L) and Bulinus truncatus the least susceptible (LC50: 4.035; LC95: 228.118 mg/L). However, for adults, B. truncatus was the most susceptible (mortality rate: 100%). The LC50 and LC95 for Bi. camerunensis eggs were 0.171 mg/L and 1.102 mg/L, respectively, and were higher than those obtained for adults (0.0357 mg/L and 0.9634 mg/L); (4) Conclusion: These findings will guide the design of vector control strategies targeting these snail species in Cameroon.

Background Humans impose a significant pressure on large herbivore populations, such as hippopotami, through hunting, poaching, and habitat destruction. Anthropogenic pressures can also occur indirectly, such as artificial lake creation and the subsequent introduction of invasive species that alter the ecosystem. These events can lead to drastic changes in parasite diversity and transmission, but generally receive little scientific attention. Results In order to document and identify trematode parasites of the common hippopotamus (Hippopotamus amphibius) in artificial water systems of Zimbabwe, we applied an integrative taxonomic approach, combining molecular diagnostics and morphometrics on archived and new samples. In doing so, we provide DNA reference sequences of the hippopotamus liver fluke Fasciola nyanzae, enabling us to construct the first complete Fasciola phylogeny. We describe parasite spillback of F. nyanzae by the invasive freshwater snail Pseudosuccinea columella, as a consequence of a cascade of biological invasions in Lake Kariba, one of the biggest artificial lakes in the world. Additionally, we report an unknown stomach fluke of the hippopotamus transmitted by the non-endemic snail Radix aff. plicatula, an Asian snail species that has not been found in Africa before, and the stomach fluke Carmyerius cruciformis transmitted by the native snail Bulinus truncatus. Finally, Biomphalaria pfeifferi and two Bulinus species were found as new snail hosts for the poorly documented hippopotamus blood fluke Schistosoma edwardiense. Conclusions Our findings indicate that artificial lakes are breeding grounds for endemic and non-endemic snails that transmit trematode parasites of the common hippopotamus. This has important implications, as existing research links trematode parasite infections combined with other stressors to declining wild herbivore populations. Therefore, we argue that monitoring the anthropogenic impact on parasite transmission should become an integral part of wildlife conservation efforts. Graphical abstract

Background Global elimination of schistosomiasis as a public health problem is set as target in the new World Health Organization’s Neglected Tropical Diseases Roadmap for 2030. Due to a long history of interventions, the Zanzibar islands of Tanzania have reached this goal since 2017. However, challenges occur on the last mile towards interruption of transmission. Our study will investigate new tools and strategies for breaking schistosomiasis transmission. Methods The study is designed as an intervention study, documented through repeated cross-sectional surveys (2020–2024). The primary endpoint will be the sensitivity of a surveillance-response approach to detect and react to outbreaks of urogenital schistosomiasis over three years of implementation. The surveys and multi-disciplinary interventions will be implemented in 20 communities in the north of Pemba island. In low-prevalence areas, surveillance-response will consist of active, passive and reactive case detection, treatment of positive individuals, and focal snail control. In hotspot areas, mass drug administration, snail control and behaviour change interventions will be implemented. Parasitological cross-sectional surveys in 20 communities and their main primary schools will serve to adapt the intervention approach annually and to monitor the performance of the surveillance-response approach and impact of interventions. Schistosoma haematobium infections will be diagnosed using reagent strips and urine filtration microscopy, and by exploring novel point-of-care diagnostic tests. Discussion Our study will shed light on the field applicability and performance of novel adaptive intervention strategies, and standard and new diagnostic tools for schistosomiasis elimination. The evidence and experiences generated by micro-mapping of S. haematobium infections at community level, micro-targeting of new adaptive intervention approaches, and application of novel diagnostic tools can guide future strategic plans for schistosomiasis elimination in Zanzibar and inform other countries aiming for interruption of transmission. Trial registration ISRCTN, ISCRCTN91431493. Registered 11 February 2020, https://www.isrctn.com/ISRCTN91431493

In recent decades, computer vision has proven remarkably effective in addressing diverse issues in public health, from determining the diagnosis, prognosis, and treatment of diseases in humans to predicting infectious disease outbreaks. Here, we investigate whether convolutional neural networks (CNNs) can also demonstrate effectiveness in classifying the environmental stages of parasites of public health importance and their invertebrate hosts. We used schistosomiasis as a reference model. Schistosomiasis is a debilitating parasitic disease transmitted to humansviasnail intermediate hosts. The parasite affects more than 200 million people in tropical and subtropical regions. We trained our CNN, a feed-forward neural network, on a limited dataset of 5,500 images of snails and 5,100 images of cercariae obtained from schistosomiasis transmission sites in the Senegal River Basin, a region in western Africa that is hyper-endemic for the disease. The image set included both images of two snail genera that are relevant to schistosomiasis transmission – that is,Bulinusspp. andBiomphalaria pfeifferi– as well as snail images that are non-component hosts for human schistosomiasis. Cercariae shed fromBi. pfeifferi and Bulinusspp. snails were classified into 11 categories, of which only two,S. haematobiumandS. mansoni, are major etiological agents of human schistosomiasis. The algorithms, trained on 80% of the snail and parasite dataset, achieved 99% and 91% accuracy for snail and parasite classification, respectively, when used on the hold-out validation dataset – a performance comparable to that of experienced parasitologists. The promising results of this proof-of-concept study suggests that this CNN model, and potentially similar replicable models, have the potential to support the classification of snails and parasite of medical importance. In remote field settings where machine learning algorithms can be deployed on cost-effective and widely used mobile devices, such as smartphones, these models can be a valuable complement to laboratory identification by trained technicians. Future efforts must be dedicated to increasing dataset sizes for model training and validation, as well as testing these algorithms in diverse transmission settings and geographies.

Schistosomiasis is a parasitic disease caused by worms of the genus Schistosoma. Some substances are used to control the intermediate host, being a strategy to prevent the risk of infection and re-infection of the disease. According to the WHO, the recommended substance is Niclosamide; however, it presents toxicity in non-target organisms. Aqueous extracts are being increasingly studied as a potential molluscicide in combating schistosomiasis. The aqueous extract of Moringa oleifera flowers was used to evaluate the molluscicidal activity in Biomphalaria glabrata. This extract caused lethality in adult molluscs, obtaining a lethal concentration 50 = 2.37 mg/mL. In the second aqueous extract, fruits of the species Randia nilotica were used on molluscs of the species Biomphalaria pfeifferi and Bulinus truncatus. These extracts showed molluscicidal activity on both molluscs used in the experiments. In the third aqueous extract, they used leaves of the species Anagallis arvensis to test the molluscicidal action on molluscs of the species Biomphalaria alexandrina. It was possible to obtain lethal concentrations, with lethal concentration 50 = 37.9 mg/L and lethal concentration 90 = 48.3 mg/L. In the fourth aqueous extract, they used the seeds of the species Moringa oleifera to evaluate the molluscicidal activity in molluscs of the genus Bulinus. These seeds showed molluscicidal action, but they were not in accordance with what is recommended by the WHO. According to the experiments carried out with aqueous extracts, it can be seen that there are many studies using these methodologies as a form of control for schistosomiasis. Some criteria are essential to obtain a low-cost aqueous extract. It is essential to emphasize that this methodology could be used by the government to control the intermediate host of schistosomiasis in less favored areas, where the population itself would have access to inputs using accessible technological resources.

Some snails act as intermediate hosts (vectors) for parasitic flatworms (flukes) that cause neglected tropical diseases, such as schistosomiases. Schistosoma haematobium is a blood fluke that causes urogenital schistosomiasis and induces bladder cancer and increased risk of HIV infection. Understanding the molecular biology of the snail and its relationship with the parasite could guide development of an intervention approach that interrupts transmission. Here, we define the genome for a key intermediate host of S. haematobium-called Bulinus truncatus-and explore protein groups inferred to play an integral role in the snail's biology and its relationship with the schistosome parasite. Bu. truncatus shared many orthologous protein groups with Biomphalaria glabrata-the key snail vector for S. mansoni which causes hepatointestinal schistosomiasis in people. Conspicuous were expansions in signalling and membrane trafficking proteins, peptidases and their inhibitors as well as gene families linked to immune response regulation, such as a large repertoire of lectin-like molecules. This work provides a sound basis for further studies of snail-parasite interactions in the search for targets to block schistosomiasis transmission.

Background Schistosomiasis is endemic in 78 countries belonging to tropical and subtropical areas. However, autochthonous transmission of urogenital schistosomiasis was reported in Corsica (France) in 2013. We present evidence of autochthonous transmission of urogenital schistosomiasis in Almeria (Spain) in 2003. Methods Description of the outbreak in farmers and subsequent epidemiological studies aimed at searching for Bulinus snails and their genotypic characteristics. Results The outbreak affected 4 farmers out of a group of 5 people who repeatedly bathed that summer in an irrigation pool in the area. Two of them presented macroscopic hematuria with bilharziomas, showing the presence of Schistosoma eggs in bladder biopsies. Two others were asymptomatic but the serology for schistosomiasis was positive. In 2015, the presence of the vector Bulinus truncatus was demonstrated in Almeria in water collections of appropriate characteristics. DNA sequencing proving that local B. truncatus species were base-to-base identical to B. truncatus from Senegal. Conclusions We present a new outbreak of autochthonous transmission of urogenital schistosomiasis in Europe. Although no new cases of autochthonous transmission have been reported, some other cases may have occurred at that time or later on and be unnoticed as many cases of schistosomiasis are asymptomatic or present mild and unspecific symptoms.

Significance Schistosomiasis is a parasitic disease that affects ∼206 million people globally. The World Health Organization recently endorsed control of the freshwater snails that host schistosome infectious stages, and here, we show how to better target those snail control efforts. Schistosomiasis infection occurred on a local scale at our study sites in northwestern Senegal, suggesting that small-scale interventions can suppress transmission. However, snail clusters were so ephemeral that attempts to target them for removal would be inefficient. Instead, we found easy-to-measure environmental proxies that were more effective than snail variables at predicting human infections, including area of snail habitat within the site and total site area. Our work indicates that satellite- or drone-based precision mapping could efficiently identify high-transmission areas., Recently, the World Health Organization recognized that efforts to interrupt schistosomiasis transmission through mass drug administration have been ineffective in some regions; one of their new recommended strategies for global schistosomiasis control emphasizes targeting the freshwater snails that transmit schistosome parasites. We sought to identify robust indicators that would enable precision targeting of these snails. At the site of the world’s largest recorded schistosomiasis epidemic—the Lower Senegal River Basin in Senegal—intensive sampling revealed positive relationships between intermediate host snails (abundance, density, and prevalence) and human urogenital schistosomiasis reinfection (prevalence and intensity in schoolchildren after drug administration). However, we also found that snail distributions were so patchy in space and time that obtaining useful data required effort that exceeds what is feasible in standard monitoring and control campaigns. Instead, we identified several environmental proxies that were more effective than snail variables for predicting human infection: the area covered by suitable snail habitat (i.e., floating, nonemergent vegetation), the percent cover by suitable snail habitat, and size of the water contact area. Unlike snail surveys, which require hundreds of person-hours per site to conduct, habitat coverage and site area can be quickly estimated with drone or satellite imagery. This, in turn, makes possible large-scale, high-resolution estimation of human urogenital schistosomiasis risk to support targeting of both mass drug administration and snail control efforts.

BACKGROUND Schistosoma haematobium infection is a major public health problem in most of Africa and the Middle East and praziquantel remains the only drug used for schistosomiasis control, therefore emergence of drug resistance is unavoidable. The antimalarial artemisinin-naphthoquine phosphate combination (co-ArNp) was recently documented to have promising effects on Schistosoma mansoni and its snail host. METHODS We conducted this in vitro study to assess the bioactivity of co-ArNp on S. haematobium and its snail vector Bulinus truncatus. RESULTS Treatment of S. haematobium worms with 1 μg/ml co-ArNp for 24 h reduced worm motility, while 20 μg/ml resulted in 25-100% mortality of adult flukes within 48-72 h. Incubation of S. haematobium miracidia and cercariae with the molluscicidal co-ArNp (50% lethal concentration 7.5 μg/ml) killed all the free larval stages within 40 and 15 min, respectively. Also, exposure of B. truncatus adult snails to 20 ppm of the combined regimen caused a mortality rate of 100% within 24 h. CONCLUSIONS Co-ArNp therapy has also shown encouraging activity against the other major human schistosome, S. haematobium, as well as its vector.

Background The Zanzibar Archipelago (Pemba and Unguja islands) is targeted for the elimination of human urogenital schistosomiasis caused by infection with Schistosoma haematobium where the intermediate snail host is Bulinus globosus. Following multiple studies, it has remained unclear if B. nasutus (a snail species that occupies geographically distinct regions on the Archipelago) is involved in S. haematobium transmission on Zanzibar. Additionally, S. haematobium was thought to be the only Schistosoma species present on the Zanzibar Archipelago until the sympatric transmission of S. bovis, a parasite of ruminants, was recently identified. Here we re-assess the epidemiology of schistosomiasis on Pemba and Unguja together with the role and genetic diversity of the Bulinus spp. involved in transmission. Methodology/Principal findings Malacological and parasitological surveys were conducted between 2016 and 2019. In total, 11,116 Bulinus spp. snails were collected from 65 of 112 freshwater bodies surveyed. Bulinus species identification were determined using mitochondrial cox1 sequences for a representative subset of collected Bulinus (n = 504) and together with archived museum specimens (n = 6), 433 B. globosus and 77 B. nasutus were identified. Phylogenetic analysis of cox1 haplotypes revealed three distinct populations of B. globosus, two with an overlapping distribution on Pemba and one on Unguja. For B. nasutus, only a single clade with matching haplotypes was observed across the islands and included reference sequences from Kenya. Schistosoma haematobium cercariae (n = 158) were identified from 12 infected B. globosus and one B. nasutus collected between 2016 and 2019 in Pemba, and cercariae originating from 69 Bulinus spp. archived in museum collections. Schistosoma bovis cercariae (n = 21) were identified from seven additional B. globosus collected between 2016 and 2019 in Pemba. By analysing a partial mitochondrial cox1 region and the nuclear ITS (1–5.8S-2) rDNA region of Schistosoma cercariae, we identified 18 S. haematobium and three S. bovis haplotypes representing populations associated with mainland Africa and the Indian Ocean Islands (Zanzibar, Madagascar, Mauritius and Mafia). Conclusions/Significance The individual B. nasutus on Pemba infected with S. haematobium demonstrates that B. nasutus could also play a role in the local transmission of S. haematobium. We provide preliminary evidence that intraspecific variability of S. haematobium on Pemba may increase the transmission potential of S. haematobium locally due to the expanded intermediate host range, and that the presence of S. bovis complicates the environmental surveillance of schistosome infections.

There is a need for recent information on intermediate snail hosts of schistosomes in The Gambia; the previous studies were conducted over three decades ago. This study assessed the incidence, species diversity, distribution and infection status of schistosome intermediate snail hosts in the country. Malacological surveys were conducted in all 5 regions of The Gambia: Central River Region (CRR), Upper River Region (URR), Western Region (WR), Lower River Region (LRR) and North Bank Region (NBR). Sampling of snails was undertaken at 114 sites that included permanent water bodies such as streams (bolongs), rice fields, irrigation canals and swamps; and temporal (seasonal) laterite pools. Ecological and physicochemical factors of sites were recorded. Snails were identified morphologically and screened for schistosome infections using molecular techniques. Freshwater snails were found at more than 50% (60/114) of sites sampled. While three species of Bulinus were collected, no Biomphalaria snails were found in any of the sites sampled. Of the total 2877 Bulinus snails collected, 75.9% were identified as Bulinus senegalensis, 20.9% as Bulinus forskalii and 3.2% as Bulinus truncatus. Seasonal pools produced the largest number of snails, and CRR was the region with the largest number of snails. Bulinus senegalensis was found more in seasonal pools as opposed to permanent sites, where B. forskalii and B. truncatus were observed to thrive. Bulinus snails were more common in seasonal sites where aquatic vegetation was present. In permanent sites, the abundance of snails increased with increase in water temperature and decrease in water pH. Bulinus senegalensis was found infected with both S. haematobium and S. bovis, while B. forskalii and B. truncatus had only S. bovis infection. While the human parasite S. haematobium was restricted to just four sites, the livestock parasite S. bovis had a much more widespread geographical distribution across both CRR and URR. This new information on the distribution of intermediate snail hosts of schistosomes in The Gambia will be vital for the national schistosomiasis control initiative., Author summary Several studies were conducted on intermediate snail hosts of schistosomes in The Gambia between the 1950s and 1980s, but there are few reports of similar studies in recent times. After The Gambia initiated its national control programme for schistosomiasis in 2014, the need arose for more and current information on schistosomiasis and the intermediate snail hosts involved indirectly in its transmission. We undertook a malacological survey of freshwater sites in all five regions (CRR, URR, WR, LRR and NBR) of The Gambia. While no Biomplalaria snails were found in any of the 114 sites sampled, three species of Bulinus snails were found. Of the total 2877 Bulinus snails collected, 75.9% were identified as Bulinus senegalensis, 20.9% as Bulinus forskalii and 3.2% as Bulinus truncatus. CRR had the highest number of snails amongst the regions and seasonal pools yielded the most snails amongst the habitat types sampled. Habitat type, water temperature and pH of sites were observed to have an influence on snail abundance. All three Bulinus snails were found infected with schistosome parasites. The human parasite (Schistosoma haematobium) had a much more restricted distribution as opposed to the livestock parasite (Schistosoma bovis) which had a wider geographical range. The study provides the first malacological report of intermediate snail hosts of schistosomes in The Gambia in over 3 decades and will be useful to the national schistosomiasis control programme.

Snails act as intermediate hosts and play active role in the transmission of trematodes. Assessments of snail vectors of public health importance in Port-Harcourt metropolis were conducted following previous report on emergence and re-emergence of schistosomiasis; in twelve locations once monthly from January to June 2019. Snails were collected in each water body using scooping net and handpicking method for 45 minutes/location and identified using shell morphology. They were screened for patent infection through exposure to sunlight individually for two hours in a petri-dish that contains clean water and checked for cercarial shedding in the laboratory using a microscope. Physico-chemical parameters (pH, temperature, dissolved oxygen (DO), conductivity, and total dissolved solid (TDS)) of the water bodies were analyzed monthly using standard methods. 1812 freshwater snails were collected and relative abundance recorded was: Lymnaea natalensis 1221(67.38%), Physa sp. 518(28.58%), Indoplanorbis exutus 44(2.42%) and Oncomelania sp. 29(1.60%). The study established the absence of Bulinus sp. in Port Harcourt metropolis and revealed that the density of fresh water snails varied monthly following wet and dry seasons. There was a significant difference in snail abundance in relation to species (F=16.24, p= 0.01 at p

Background The Lake Victoria basin is one of the most persistent hotspots of schistosomiasis in Africa, the intestinal form of the disease being studied more often than the urogenital form. Most schistosomiasis studies have been directed to Schistosoma mansoni and their corresponding intermediate snail hosts of the genus Biomphalaria, while neglecting S. haematobium and their intermediate snail hosts of the genus Bulinus. In the present study, we used DNA sequences from part of the cytochrome c oxidase subunit 1 (cox1) gene and the internal transcribed spacer 2 (ITS2) region to investigate Bulinus populations obtained from a longitudinal survey in Lake Victoria and neighbouring systems during 2010–2019. Methods Sequences were obtained to (i) determine specimen identities, diversity and phylogenetic positions, (ii) reconstruct phylogeographical affinities, and (iii) determine the population structure to discuss the results and their implications for the transmission and epidemiology of urogenital schistosomiasis in Lake Victoria. Results Phylogenies, species delimitation methods (SDMs) and statistical parsimony networks revealed the presence of two main groups of Bulinus species occurring in Lake Victoria; B. truncatus/B. tropicus complex with three species (B. truncatus, B. tropicus and Bulinus sp. 1), dominating the lake proper, and a B. africanus group, prevalent in banks and marshes. Although a total of 47 cox1 haplotypes, were detected within and outside Lake Victoria, there was limited haplotype sharing (only Haplotype 6 was shared between populations from Lake Victoria open waters and neighbouring aquatic systems) – an indication that haplotypes are specific to habitats. Conclusions The Bulinus fauna of Lake Victoria consists of at least B. truncatus, B. tropicus, Bulinus sp. 1 (B. trigonus?) and B. ugandae. The occurrence and wide distribution of Bulinus species in Lake Victoria potentially implies the occurrence of urogenital schistosomiasis in communities living along the shores and on islands of the lake who depend solely on the lake for their livelihood. More in-depth studies are needed to obtain a better picture of the extent of the disease in the Lake Victoria basin.

BackgroundBulinusspecies are freshwater snails that transmit the parasitic trematodeSchistosoma haematobium. Despite their importance, the diversity of these intermediate host snails and their evolutionary history is still unclear in Zimbabwe.Bulinus globosusandB. truncatuscollected from a urogenital schistosomiasis endemic region in the Madziwa area of Zimbabwe were characterized using molecular methods.MethodsMalacological survey sites were mapped and snails were collected from water contact sites in four communities in the Madziwa area, Shamva district for a period of one year, at three-month intervals.Schistosoma haematobiuminfections in snails were determined by cercarial shedding and the partial mitochondrial cytochromecoxidase subunit 1 gene (cox1) was used to investigate the phylogeny and genetic variability of theBulinusspp. collected.ResultsAmong the 1570Bulinusspp. snails collected, 30 (1.9%)B. globosuswere shedding morphologically identified schistosomes. None of theB. truncatussnails were shedding. The mitochondrialcox1 data from 166 and 16 samples forB. globosusandB. truncatus, respectively, showed genetically diverse populations within the two species. Twelvecox1 haplotypes were found from the 166B. globosussamples and three from the 16B. truncatussamples with phylogenetic analysis showing that the haplotypes fall into well-supported clusters within their species groups. BothB. truncatusandB. globosusclustered into two distinct lineages. Overall, significant negative values for both Tajima’s D statistic and the Fu’s Fs statistic were observed forB. globosusandB. truncatus.ConclusionsThe study provided new insights into the levels of genetic diversity withinB. globosusand additional information onB. truncatuscollected from a small geographical area in Zimbabwe. Low prevalence levels of infection observed in the snails may reflect the low transmission level of urogenital schistosomiasis in the area. Our results contribute towards the understanding of the distribution and population genetic structure ofBulinusspp. supporting the mapping of the transmission or risk of transmission of urogenital schistosomiasis, particularly in Zimbabwe.

BackgroundPreventive chemotherapy with praziquantel is the cornerstone of schistosomiasis control. However, in some social-ecological settings, the prevalence and/or intensity of Schistosoma infection does not lower meaningfully despite multiple rounds of preventive chemotherapy, a phenomenon termed persistent hotspot (PHS). We assessed the characteristics of PHS in a Schistosoma mansoni-endemic area of Côte d’Ivoire.Methods: In October 2016, a cross-sectional parasitological survey was conducted in 14 schools in the western part of Côte d’Ivoire, one year after multiple rounds of preventive chemotherapy. In each school, 50 children aged 9-12 years were randomly selected and invited to submit two stool samples and one urine sample. Stool samples were subjected to triplicate Kato-Katz thick smears for S. mansoni diagnosis. Urine samples were examined by a filtration method for S. haematobium eggs. PHS was defined as failure to achieve a reduction in the prevalence and/or intensity of S. mansoni infection of at least 35% and 50%, respectively after multiple rounds of preventive chemotherapy targeting school-aged children. A questionnaire was administered in six schools to obtain data on demographic characteristics, including human-water contact behaviours, water, sanitation and hygiene and history of preventive chemotherapy. A malacological survey was conducted in December 2016.Results: The overall prevalence of S. mansoni and S. haematobium in the 14 surveyed schools was 9.5% and 2.6%, respectively. There were four PHS among six schools that underwent detailed investigation. The S. mansoni prevalence in the four PHS was 10.9% (95% confidence interval (CI): 6.4-15.5%), compared to 6.6% (95% CI: 1.4-11.8%) in the remaining two schools. The arithmetic mean of S. mansoni eggs per gram of stool (EPG) among infected children was 123.8 EPG in PHS and 18.7 EPG in the remaining two schools. A statistically significant difference between PHS and the other schools regarding praziquantel coverage was found with higher coverage rate observed in PHS (98.4% versus 89.0%, X2 = 3.7, p = 0.001). There was no significant difference with regard to access to clean water in the two groups of schools. Children bathing in open freshwater bodies were at higher odds of S. mansoni infection (odds ratio (OR) = 4.5, 95% CI: 1.6-12.6). A total of 76 human-water contact sites (53 in PHS and 23 in the other schools) were examined and 688 snails were collected, including 92 Biomphalaria pfeifferi, 25 Bulinus forskalii, 16 Bu. globosus and one Bu. truncatus.Conclusion: Children in PHS schools bathed more frequently in open freshwater bodies, and hence, they were potentially more exposed to S. mansoni. Our findings call for an integrated control approach, complementing preventive chemotherapy with behavioural change implementation in PHS settings.

Background: Immunology studies include three main areas: infection, re-infection resistance to re-infection of schistosomiasis, and diagnosis. Objective: In this study, the author reports a study of immunology of schistosomiasis that focused on some important issues include mammalian host, important species of schistosomes, life cycle, host’s immune response, and diagnosis as objectives of this study. Methodology: The author searched Google, Science Direct and the PubMed Database of NCBI for articles on immunology of schistotomiasis published between 2009 and 2021. Articles were unrestricted open access, articles with permissions from Elsevier if required, and in English. Other relevant publications were also included. Results: Commonly, three Schistosoma species can infect humans. These include Schistosoma haematobium, Schistosoma japonicum, and Schistosoma mansoni. Schistosoma haematobium can infect such as baboons, humans, monkeys, and rhesus monkey. Schistosoma japonicum can infect such as humans, buffalos, dogs, and wild pigs. Schistosoma mansoni can infect humans and wild primates. The genus Schistosoma has two hosts: intermediate hosts and definite hosts. Intermediate hosts of S. haematobium, S. japonicum, and S. mansoni are the genus Bulinus, genus Oncomelania and genus Biomphalaria, respectively. In humans, cercariae released by intermediate hosts reach, and penetrate human skin. When cercariae reach human, it induce type 1 (Th1) immune responses and elevates such as IL-12 and TNFα. With worms reach adults, it induces Th2 immune response and elevates such as IL-4 and IL-13, and cause Th1 decrease. Increase of Th2 causes the development of hepatic granulomatous and fibrosis. Treatment can decrease Th2 and significantly hepatic granulomatous formation and fibrosis. In addition, it can reduce schistosomiasis cases. However, re-infection can occur in people who live in endemic areas. For diagnosing schistosomiasis, there are several tools can be used. These include such as microscopic and molecular tools. Conclusion: Th1 immune responses elevate serum cytokine levels such as IL-12 and TNFα. When Th1 is decreased, it elevates Th2 immune responses and level of cytokines such as IL-4 and TGF-β. This causes the development of granulomatous and fibrosis, even diseases such as cancer. Re-infection of schistomiasis can occur in people that have been treated, especially in the endemic areas. Tools for detecting schistosomiasis infection can include such as microscope and molecular methods.

Background: The genus Schistosoma infects snails such as Bulinus spp., Oncomelania spp., and Biomphalaria spp. Host-parasite interaction of schistosomiasis includes induction of T helper type 1 (Th2) and reactive oxygen species (ROS). Objectives: This study, the author describes about intermediate host and host-parasite interaction in schistosomiasis as objectives of this study. Methodology: The author searched the information on the internet for articles on S. japonicum schistosomiasis. Articles were unrestricted open access, permissions from Elsevier, in English, and relevant publications were also included. Results: Intermediate host of S. haematobium consists of such as B. camerunsis, B. forskalii, B. globusus, and B. tropica. Intermediate host of S. japonicum consists of such as O. hupensis chiui, O. hupensis hupensis, O. hupensis linduensis, and O. hupensis quadrasi. Intermediate host of S. mansoni consists of such as B. alexandrina, B. angulosa, B. choanomphala, and B. glabrata. There are other Schistosoma spp. that can infect humans. These include such as S. intercalatum, S. malayensis, and S. mekongi. Intermediate host of S. intercalatum is B. forskalii. Intermediate host of S. malayensis is Robertsiella karporensis. Intermediate host of S. mekongi is Neotricula aperta. For the host-parasite interaction, it may include response of the host to parasite substances, induction of T helper type 2 (Th2) responses to parasite eggs. Exposure of the host to life cycle stage elicits a polarized Th2 response to antigens. Schistosoma infection result in granuloma formation as a protective mechanism. However, it is also responsible for the disease development. Reactive oxygen species (ROS) from the snail is in attempt to stop the parasite’s development. Conclusions: Intermediate hosts of the genus Schistosoma include such as Bulinus spp. Oncomelania spp., and Biomphalaria spp. Host-parasite interaction can include such as induction of Th2 and ROS and granulomas formation and the development of the disease.

Bulinid snails act as intermediate host of schistosomes and the presence of the snail gives schistosomiasis an expansive characteristics. Schistosomiasis is of medical and veterinary importance in the tropical and subtropical regions. The shell shape and structure of radula teeth of bulinids are often specific to a species or genus, and are widely used for gastropod species identification. Bulinid species collected from schistosome endemic areas of Ogun State, South-western Nigeria were used for this study. Shell morphometrics were recorded using vernier caliper while the buccal mass of each snail was removed and permanent slides of the radulae were made according to standard procedure. There was a significant difference in the shell height, width, aperture height and aperture width between Bulinus globosus and Bulinus jousseaumei (p

Snail-borne trematodiases, such as fascioliasis and schistosomiasis, belong to the neglected tropical diseases; yet, millions of people and livestock are affected. The spatial and temporal distribution of intermediate host snails plays an important role in the epidemiology and control of trematodiases. Snail distribution is influenced by numerous environmental and anthropomorphic factors. The aim of this study was to assess the distribution and constitution of the snail fauna during the dry season in constructed and natural water bodies in the Tchologo region, northern Cote d’Ivoire, and to relate these findings to environmental factors and human infections. Snails were collected using standard procedures and environmental parameters were assessed from a total of 50 water bodies in and around 30 randomly selected villages. A canonical correspondence analysis was performed to establish the relationship between snail occurrence and environmental factors. Furthermore, a total of 743 people from the same 30 villages and nearby settlements were invited for stool and urine examination for the diagnosis of Fasciola spp., Schistosoma haematobium and Schistosoma mansoni. Snails of medical importance of the genera Biomphalaria, Bulinus, Lymnaea and Physa were found. Differences in snail occurrence from sites sampled in December 2014 and snails sampled in February 2015, as well as between the northern and southern part of the study area, were revealed. Various environmental factors, such as temperature and human activities, were related to the occurrence of intermediate host snail species in the region. Only 2.3% of human participants tested positive for schistosomiasis, while no Fasciola eggs were found in stool samples. We conclude that intermediate host snails of Fasciola and Schistosoma co-occur in water bodies in the Tchologo region and that the distribution of these snails correlates not only with environmental factors, but also with the presence of humans and animals and the environmental contamination of their excreta.

A comparative study of the shell structure, seasonal temperature and Calcium content of Bulinus snails from two areas (Damietta and Giza) in Egypt was done and compared with laboratory snails from Schistosome Biological Supply Center (SBSC). The shells of collected snails identified as Bulinus truncatus, showed a wide variation in shape. The results showed a significant differences were detected between the populations from SBSC and Damietta (p

Background: The epidemiology of human urinary schistosomiasis caused by Schistosoma haematobium can be complicated by the presence of ruminant schistosomiasis caused, primarily by S. bovis. The two schistosome species may be transmitted by the same Bulinus species, they may occur sympatrically in the same habitat, and their cercariae are very similar in morphology and therefore, difficult to tell them apart. Screening of snails collected from freshwater habitats for schistosome infections is often used to identify transmission sites or to evaluate success or failure of interventions. However, pin-pointing sites involved in S. haematobium transmission can be complicated by the presence of other mammalian schistosomes such as the bovine schistosome, which is a fairly common parasite. A PCR-RFLP method targeting a unique segment of the second internal transcribed spacer (ITS2) region of the ribosomal DNA (rDNA) in the schistosomes was used to identify mammalian schistosome cercariae shed by bulinid snails collected from endemic freshwater habitats located within Machakos county in south-eastern Kenya, with the aim to identify the transmission sites and assess the distribution each of the parasite species in the study area. Results: A total of 5,034 bulinid snails were collected from 41 different sites and screened for schistosome infections, and out of these, 43 (

Schistosomiasis is a widespread parasitic infection whose intermediate host is aquatic snails and affects more than 250 million people worldwide. Although control of the snails with synthetic molluscicides is possible, it is not greatly preferred due to concerns of environmental toxicity and the relatively high cost of the chemicals. Conversely, organic plant-derived molluscicides are a better alternative that can be used to reduce the incidence of the disease. The objective of this study was to evaluate the molluscicidal activity of the plants Phytolacca octandra, P. dodecandra and Balanites aegypiaca. The major parts of the whole plant (berries, leaves, stems and roots) were collected, air dried to constant weight, macerated to a fine powder and extracted separately using methanol in soxhlet apparatus. The extracts were screened for activity using brine shrimp lethality test and thereafter tested for molluscicidal activity. There was no significant difference observed in the activity of the plant parts studied and of the three plant species in the brine shrimp lethality test. Similarly, no significant difference in molluscicidal activity of the plant parts studied and in the three plants against bulinus snails was detected. It was concluded that that the three plants can be used in the control of schistosomiasis transmitting snails. Key words: Schistosomiasis, molluscicidal, Bulinus snails, brine shrimp, Phytolacca octandra, Phytolacca dodecandra, Balanites aegypiaca

The freshwater snail Bulinus globosus is an important intermediate host of Schistosoma haematobium, the causative agent of urinary schistosomiasis. This disease is of major health concern, especially in Africa where the majority of cases have been reported. In this study the inter- and intra-genetic diversity and population genetic structure of B. globosus from nine locations in the KwaZulu-Natal province of South Africa was studied using four polymorphic microsatellite loci (BgZ1-BgZ4). Moderate genetic diversity was detected within populations with a mean diversity (HE) of 0.49±0.09. The majority of populations significantly deviated from Hardy-Weinberg equilibrium (p

Schistosomiasis – a parasitic disease that affects over 200 million people across the globe – is primarily transmitted between human definitive hosts and snail intermediate hosts. To reduce schistosomiasis transmission, some have advocated disrupting the schistosome life cycle through biological control of snails, achieved by boosting the abundance of snails' natural predators. But little is known about the effect of parasitic infection on predator–prey interactions, especially in the case of schistosomiasis. Here, we present the results of laboratory experiments performed on Bulinus truncatus and Biomphalaria glabrata snails to investigate: (i) rates of predation on schistosome-infected versus uninfected snails by a sympatric native river prawn, Macrobrachium vollenhovenii, and (ii) differences in snail behavior (including movement, refuge-seeking and anti-predator behavior) between infected and uninfected snails. In predation trials, prawns showed a preference for consuming snails infected with schistosome larvae. In behavioral trials, infected snails moved less quickly and less often than uninfected snails, and were less likely to avoid predation by exiting the water or hiding under substrate. Although the mechanism by which the parasite alters snail behavior remains unknown, these results provide insight into the effects of parasitic infection on predator–prey dynamics and suggest that boosting natural rates of predation on snails may be a useful strategy for reducing transmission in schistosomiasis hotspots.

Due to survival of intermediate hosts of parasites causing schistosomiasis and fascioliasis under changing environmental conditions, this research was conducted to investigate the distribution and diversity of freshwater snails between March and June, 2017. Physico-chemical parameters were analyzed according to the standard operating procedures for examination of water and wastewaters. Snails were sampled using an Ekman grab from different sites in each reservoir, counted and identified using standard identification guide. A total of 108 snails were collected and identified in Kubanni reservoir comprising Biomphalaria sp. (48.15%), Lymnaea sp. (39.81%) and Bulinus sp. (12.04%). While in Weir, 141 snails which comprised Biomphalaria sp. (53.19%), Lymnaea sp. (24.11%) and Bulinus sp. (22.70%) were collected. Shanon-Weiner diversity index for Kubanni and Weir were 0.97 and 1.02 respectively. Variation in physico-chemical parameters between the reservoirs shows no significant difference (P>0.05), except for electrical conductivity (EC; p-0.0015), total dissolved solid (TDS; p-0.0016), biochemical oxygen demand (BOD; p-0.0004) and concentration of phosphate (PO4.-0.026) The three snail species obtained were common to the two reservoirs; however species diversity is higher in Kubanni reservoir than Weir. The presence of these snails in the two reservoirs could pose a serious threat to humans coming in contact with these reservoirs, in their role as intermediate hosts of parasites that causes schistosomiasis and fascioliasis.

In this article, the main amphistome species infecting domestic and wild ruminants in East and Southern Africa, their snail intermediate hosts and epidemiological features are reviewed and discussed. Twenty-six amphistome species belonging to nine genera from three families occur in domestic and wild ruminants in the region under review and over 70% of them belong to the genera Calicophoron, Carmyerius and Cotylophoron . Of the amphistome species, 76.9% are shared between domestic and wild ruminant hosts – an important observation when considering the different options for control. Seven freshwater snail species belonging to four genera from two families act as intermediate hosts of the identified amphistome species, with the genus Bulinus contributing 57% of the snail species. Some of the snails are intermediate hosts of amphistome species belonging to the same genus or to different genera; a phenomenon not yet fully elucidated as some snails are reported to be naturally infected with amphistome cercariae of unidentified species. Only nine (34.6%, 9/26) of the amphistome species have known snail intermediate hosts, while most (65.4%, 17/26) have unknown hosts. Species of intermediate hosts and the potential of the flukes to infect these hosts, the biological potential of the snail hosts, the definitive hosts management systems and their grazing habits are considered to be the main factors influencing the epidemiology of amphistomosis. Based on the epidemiological features of amphistome infections, various practical control options are discussed. Further research is necessary to determine amphistome–snail associations, develop diagnostic tests that can detect prepatent infections in the definitive host, determine the burden and economic importance of amphistomosis in domestic and wild ruminants and the efficacy of different anthelmintics in the treatment of patent infections.

Globally over 200 million people are infected with schistosomiasis, and approximately 80% are caused by just two of five species, Schistosoma haematobium and Schitosoma mansoni that are broadly distributed, and often overlap across sub-Saharan Africa. Like most neglected tropical diseases, mortality is low (an estimated 200,000 deaths annually) and morbidity is considerably high and probably underestimated. Surprisingly, little attention has been given to co-infection with these two species. We have studied co-infection with S. mansoni and S. haematobium in a peri-urban community in Ghana, one of the most highly endemic countries for schistosomiasis. We collected and examined snails of the two intermediate host species from the reservoir adjacent to the community. We also used microscopical examination of stool and urine samples to determine the level of concurrent S. mansoni and S. haematobium infections in school and administered questionnaires to assess water contact activities that predispose pupils to infections Examination of the snail hosts revealed that 0.7% (7/896) of Bulinus truncatus and 1.7% (14/780) of Biomphalaria pfeifferi snails were found to be hosting cercariae morphologically consistent with that of S. haematobium and S. mansoni respectively. The overall prevalence values for urogenital and intestinal schistosomiasis were 66.8% (135/202) and 90.1% (163/181) respectively. Only 50 of 181 schistosome-infected pupils had single-species infections and the remaining 131 pupils presented concurrent infections. Among the 131 infected with both species were 50 individuals having only S. mansoni eggs in stool and S. haematobium eggs in urine (conventional presentation). Eighty-one children (81) had eggs of both species in either urine and/or stool (ectopic presentation). From these 81, 63 had eggs of both species in urine, 6 had both species in stool, and 12 had eggs of both species present in both urine and stool. A comparatively large number of individuals from the concurrent infected group presented high and moderate infection intensities than the single infected groups. The overwhelmingly high prevalence of concurrent infections indicates further study of co-infection is needed, and points to a need call for a holistic disease control plan so Ghana can be part of nations to achieve the WHO roadmap target for schistosomiasis control by 2020.

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 Schistosoma haematobium infection in endemic areas varies depending on the nature and complexity of the transmission networks present. Studies of micro-geographical transmission of S. haematobium infection indicate that discrepancy in prevalence between households is associated with diverse water contact behaviors and transmission that is restricted to particular sites harboring snail intermediate hosts. Detection of variations in the transmission sources with complex transmission networks of water bodies is required for optimization of malacological control. Longitudinal parasitological and malacological surveys were conducted to investigate geographical variations in transmission of urogenital schistosomiasis in Ikingwamanoti village, Shinyanga District, Tanzania. Methods Urine samples were collected at baseline and follow-up time points from 282 school-aged children and examined microscopically for the presence of S. haematobium eggs. Malacological surveys involved collection of Bulinus nasutus every month from 30 sites. Snails were examined for patent infections. Global positioning system was used to map household distances from S. haematobium transmission sites, while water contact behavior was assessed using a questionnaire. Results Schistosoma haematobium infection was observed to be prevalent among older children (12–14 years) compared to younger groups prior to treatment, but no significant difference in infection prevalence was observed at one-year. Boys were highly infected than girls at both time points. No spatial influence was observed between children’s infection and the distance from child’s residence to the nearby snail habitats nor was any significant association observed between children’s reported water contact behavior with S. haematobium infection. However, malacological surveys with cercarial shedding combined with GPS data detected significant variation among different water sources in the transmission of S. haematobium with children living in households near to ponds with high B. nasutus populations having the highest prevalence of infection. Conclusions Interaction between malacological surveys with cercarial shedding combined with GPS mapping in endemic settings can help detection of transmission sources even in areas with complex transmission networks. Subsequent studies are needed to determine whether the combination of GPS mapping and parasitology screens can aid the detection of transmission hotspots across varied transmission settings to enhance schistosomiasis control programmes. Electronic supplementary material The online version of this article (10.1186/s13071-018-3064-5) contains supplementary material, which is available to authorized users.

RESUMEN Fundamentos. En Europa no era endémica la esquistosomiasis urogenital, sin embargo en 2014 aparecieron en Francia los primeros casos de un brote de infección autóctona europea. En este trabajo se hace una búsqueda y descripción de casos de esquistosomiasis urogenital, tanto importados como autóctonos, publicados en la Unión Europea (UE) durante los últimos 20 años. Además se realiza una evaluación cualitativa del riesgo en España. Métodos. Se realizó una búsqueda bibliográfica en PubMed de casos publicados en la UE durante los últimos 20 años (1997-2017). Se buscaron trabajos en PubMed, ResearchGate y Google Académico que evidenciasen la presencia hospedadores intermediarios Bulinus truncatus y Planorbarius metidjensis en nuestro país. Finalmente se evaluó el riesgo de esquistosomiasis urogenital en España aplicando la guía del ECDC de 2011. Resultados. Se hallaron 481 casos en la UE, 328 eran importados y 152 autóctonos. En todos los casos autóctonos el foco se localizó en Córcega, donde enfermaron personas de diversas nacionalidades. Se documentó la presencia de dos especies hospedadores potenciales en diversas localizaciones de nuestra geografía. El resultado de la evaluación de riesgo en España fue bajo riesgo. Conclusiones. Si bien el resultado de la evaluación de riesgo en España fue bajo riesgo, factores como la presencia de hospedadores intermediarios, el aumento de los flujos migratorios, y el papel que tuvo el híbrido S. haematobium-bovis en el brote de Córcega, deben poner en sobre aviso a la comunidad médica y las autoridades sanitarias ante la posibilidad de que aparezcan casos autóctonos en nuestro país.

Background. In Europe, urogenital schistosomiasis was not endemic, however in 2014 the first cases of a European autochthonous infection outbreak appeared in Corsica (France). In this work a search and description of cases, both import and native urogenital schistosomiasis, published in the European Union (EU) during the last 20 years was made. In addition, a qualitative risk assessment in Spain was carried out. Methods. A bibliographic search of European Union published cases over the last 20 years (1997-2017) was performed using PubMed. Works that evidenced the presence of intermediate hosts Bulinus truncaus and Planorbarius metidjensis in our country were searched in PubMed, ResearchGate and Google Scholar. Finally, a risk assessment of urogenital schistosomiasis in Spain using the 2011 ECDC guide was made. Results. 481 cases in the EU were found. 328 were imported and 152 autochthonous. All from the autochthonous cases were focused in Corsica, where people from different nationalities got sicked. The presence of two potential host species was documented in different locations of our geography. The result of the risk assessment in Spain was low risk. Conclusions. Although the risk assessment in Spain was low risk, several factors as the presence of intermediate hosts in Spain, the increase on migratory flows, and the role that the S. haemalobium-bovis hybrid had in the outbreak of Corsica, must alert community and health authorities about the possibility that autochthonous cases in our country appear.

SUMMARYThe epidemiology of trematode infections in cattle was investigated within highland and lowland areas of Iringa Rural District, in southern Tanzania. Fecal samples were collected from 450 cattle in 15 villages at altitudes ranging from 696 to 1800 m above the sea level. Freshwater snails were collected from selected water bodies and screened for emergence of cercariae. The infection rates in cattle wereFasciola gigantica28·2%, paramphistomes 62·8% andSchistosoma bovis4·8%. Notably, prevalence of trematode infections in cattle was much higher in highland (altitude > 1500 m) as compared with lowland (altitude < 1500 m) areas and was statistically significant (P-value = 0·000) forF. giganticaand paramphistomes but not forS. bovis. The snails collected includedLymnaea natalensis, Bulinus africanus, Bulinus tropicus, Bulinus forskali, Biomphalaria pfeifferi, Melanoides tuberculataandBellamya constrictawith a greater proportion of highland (75%) than lowland (36%) water bodies harbouring snails. Altitude is a major factor shaping the epidemiology ofF. giganticaand paramphistomes infections in cattle in Iringa Rural District with greater emphasis upon control needed in highland areas.

Freshwater snails of the genus Bulinus O. F. Muller, 1781 are intermediate hosts for schistosomes, trematode parasites which cause schistosomiasis. The genus includes closely related species complexes with restricted gene flow between populations of each taxon. Despite their importance as intermediate hosts, unambiguous identification of these snails remains challenging. We applied molecular approach to their identification to achieve a better understanding of the epidemiology of schistosomiasis in an endemic region, south-western Nigeria. A total of 149 snails were collected and their genomic DNA was screened for schistosome infection using PCR amplification of schistosome DraI repeat sequence. The snails were identified by PCR-RFLP and/or sequencing of an amplicon of their entire ITS region including the 5.8S ribosomal RNA (rRNA) gene. Four Bulinus species, namely B. globosus (Morelet, 1866), B. forskalii (Ehrenberg, 1831), B. camerunensis Mandahl-Barth, 1957 and B. senegalensis O. F. Muller, 1781 were identified, and 34.9% (n = 52) of the 149 snails were infected: B. globosus 25.5% (n = 38), B. forskalii 5.4% (n = 8), B. camerunensis 2.7% (n = 4) and B. senegalensis 1.3% (n = 2). Restriction fragment profiles of the ribosomal ITS region for B. globosus closely matched those obtained in our previous study thus confirming the view that ribosomal ITS region of these snails could be well suited for taxonomic studies. The use of sequencing for species identification was costly and time-consuming, but it was effective in resolving true identities of snails whose restriction profiles were similar and inconclusive. key wOrds: species identification, Bulinus, ITS, rRNA gene, schistosome, schistosomiasis, Nigeria

Objective To determine the ability of the Ampullariid, Lanistes varicus to prey on egg masses and juveniles of Bulinus truncatus snails, an intermediate host of urogenital schistosomiasis in West Africa. Results Lanistes varicus was found to feed voraciously on egg masses and juveniles of Bulinus truncatus, consuming all egg masses (20 –25) exposed to it within 24 h. Also, 95–100% of 1–2 days old B. truncatus snails exposed to a single L. varicus snail was consumed within 4 days. The presence of L. varicus snails greatly increased mortality in B. truncatus with mortality increasing with increase in the number of L. varicus snails in the mixture of the two snail species. The current study has demonstrated under laboratory conditions that the Ghanaian strain of L. varicus has the potential of limiting the population of B. truncatus snails, and contribute to the control of urogenital schistosomiasis in West Africa. Electronic supplementary material The online version of this article (doi:10.1186/s13104-017-2837-9) contains supplementary material, which is available to authorized users.

Background The speedy rate of change in the environmental and socio-economics factors may increase the incidence, prevalence and risk of schistosomiasis infections in Zambia. However, available information does not provide a comprehensive understanding of the biogeography and distribution of the disease, ecology and population dynamics of intermediate host snails. The current study used an information-theoretical approach to understand the biogeography and prevalence schistosomiasis and identified knowledge gaps that would be useful to improve policy towards surveillance and eradication of intermediate hosts snails in Zambia. Methods To summarise the existing knowledge and build on past and present experiences of schistosomiasis epidemiology for effective disease control in Zambia, a systematic search of literature for the period 2000–2017 was done on PubMed, Google Scholar and EBSCOhost. Using the key words: ‘Schistosomiasis’, ‘Biomphalaria’, ‘Bulinus’, ‘Schistosoma mansoni’, ‘Schistosoma haematobium’, and ‘Zambia’, in combination with Booleans terms ‘AND’ and ‘OR’, published reports/papers were obtained and reviewed independently for inclusion. Results Thirteen papers published in English that fulfilled the inclusion criteria were selected for the final review. The papers suggest that the risk of infection has increased over the years and this has been attributed to environmental, socio-economic and demographic factors. Furthermore, schistosomiasis is endemic in many parts of the country with infection due to Schistosoma haematobium being more prevalent than that due to S. mansoni. This review also found that S. haematobium was linked to genital lesions, thus increasing risks of contracting other diseases such as HIV and cervical cancer. Conclusions For both S. haematobium and S. mansoni, environmental, socio-economic, and demographic factors were influential in the transmission and prevalence of the disease and highlight the need for detailed knowledge on ecological modelling and mapping the distribution of the disease and intermediate host snails for effective implementation of control strategies. Electronic supplementary material The online version of this article (10.1186/s40249-018-0424-5) contains supplementary material, which is available to authorized users.