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Background: The control of schistosomiasis is particularly difficult in sub-Saharan Africa, which currently harbours 95% of this disease. The target population for preventive chemotherapy (PC) is expanded to all age group at risk of infection, thus increasing the demands of praziquantel (PZQ) tablets according to the new released guideline by World Health Organization. Due to the gap between available PZQ for PC and requirements, alternative approaches to assess endemicity of schistosomiasis in a community, are urgently needed for more quick and precise methods. We aimed to find out to which degree the infection status of snails can be used to guide chemotherapy against schistosomiasis. Methods: We searched literature published from January 1991 to December 2022, that reported on the prevalence rates of Schistosoma mansoni, S. haematobium in the intermediate snails Biomphalaria spp. and Bulinus spp., respectively, and in humans. A random effect model for meta-analyses was used to calculate the pooled prevalence estimate (PPE), with heterogeneity assessed using I-squared statistic (I2), with correlation and regression analysis for the exploration of the relationship between human S. mansoni and S. haematobium infections and that in their specific intermediate hosts. Results: Forty-seven publications comprising 59 field investigations were included. The pooled PPE of schistosomiasis, schistosomiasis mansoni and schistosomiasis haematobium in humans were 27.5% [95% confidence interval (CI): 24.0–31.1%], 25.6% (95% CI: 19.9–31.3%), and 28.8% (95% CI: 23.4–34.3%), respectively. The snails showed an overall infection rate of 8.6% (95% CI: 7.7–9.4%), with 12.1% (95% CI: 9.9–14.2%) in the Biomphalaria spp. snails and 6.9% (95% CI: 5.7–8.1%) in the Bulinus spp. snails. The correlation coefficient was 0.3 (95% CI: 0.01–0.5%, P < 0.05) indicating that the two variables, i.e. all intermediate host snails on the one hand and the human host on the other, were positively correlated. Conclusions: The prevalence rate of S. mansoni and S. haematobium is still high in endemic areas. Given the significant, positive correlation between the prevalence of schistosomes in humans and the intermediate snail hosts, more attention should be paid to programme integration of snail surveillance in future. [ABSTRACT FROM AUTHOR]

In order to control schistosomiasis, a strategy involves eliminating the intermediate host responsible for its transmission. Plant-derived molluscicides have been extensively researched as a cost-effective approach to combat this disease, seeking alternative solutions to synthetic molluscicides. The study aimed to analyze the phytoconstituents and assess the molluscicidal impact of ethanolic extracts on adult Bulinus truncatus snails. Dried plant materials were ground into powder, and then extracted using ethanol 96%. Preliminary phytochemical screening was carried out using standard procedures. In vitro molluscicidal activity was evaluated for the three plants extracts in different concentrations (125, 250, 500 and 1000 ppm). Every 5 adult snails were placed in a plastic cup containing a specific amount of dechlorinated water with plant sample. Control negative was prepared by placing the snails in dechlorinated water only, the numbers of survived and dead snails were recorded after 24 and 48 hours. The Lethal dose and Standard deviation were calculated. The phytochemical screening revealed the presence of different chemical constituents in the three plants samples. The result showed that all the plants extracts possessed molluscicidal activity against B. truncatus snails. The A. indica leaf extract was the most effective with LD50 of 74.32544 ppm. From the findings of this study, Molluscicide of plant origin could be useful against the common snail species in Sudan; therefore, the selected plants can play a big role in community based schistosomiasis control. [ABSTRACT FROM AUTHOR]

Abstract Background The control of schistosomiasis is particularly difficult in sub-Saharan Africa, which currently harbours 95% of this disease. The target population for preventive chemotherapy (PC) is expanded to all age group at risk of infection, thus increasing the demands of praziquantel (PZQ) tablets according to the new released guideline by World Health Organization. Due to the gap between available PZQ for PC and requirements, alternative approaches to assess endemicity of schistosomiasis in a community, are urgently needed for more quick and precise methods. We aimed to find out to which degree the infection status of snails can be used to guide chemotherapy against schistosomiasis. Methods We searched literature published from January 1991 to December 2022, that reported on the prevalence rates of Schistosoma mansoni, S. haematobium in the intermediate snails Biomphalaria spp. and Bulinus spp., respectively, and in humans. A random effect model for meta-analyses was used to calculate the pooled prevalence estimate (PPE), with heterogeneity assessed using I-squared statistic (I 2 ), with correlation and regression analysis for the exploration of the relationship between human S. mansoni and S. haematobium infections and that in their specific intermediate hosts. Results Forty-seven publications comprising 59 field investigations were included. The pooled PPE of schistosomiasis, schistosomiasis mansoni and schistosomiasis haematobium in humans were 27.5% [95% confidence interval (CI): 24.0–31.1%], 25.6% (95% CI: 19.9–31.3%), and 28.8% (95% CI: 23.4–34.3%), respectively. The snails showed an overall infection rate of 8.6% (95% CI: 7.7–9.4%), with 12.1% (95% CI: 9.9–14.2%) in the Biomphalaria spp. snails and 6.9% (95% CI: 5.7–8.1%) in the Bulinus spp. snails. The correlation coefficient was 0.3 (95% CI: 0.01–0.5%, P

Abstract Background Along the southern shoreline of Lake Malawi, the incidence of schistosomiasis is increasing with snails of the genera Bulinus and Biomphalaria transmitting urogenital and intestinal schistosomiasis, respectively. Since the underlying distribution of snails is partially known, often being focal, developing pragmatic spatial models that interpolate snail information across under-sampled regions is required to understand and assess current and future risk of schistosomiasis. Methods A secondary geospatial analysis of recently collected malacological and environmental survey data was undertaken. Using a Bayesian Poisson latent Gaussian process model, abundance data were fitted for Bulinus and Biomphalaria. Interpolating the abundance of snails along the shoreline (given their relative distance along the shoreline) was achieved by smoothing, using extracted environmental rainfall, land surface temperature (LST), evapotranspiration, normalised difference vegetation index (NDVI) and soil type covariate data for all predicted locations. Our adopted model used a combination of two-dimensional (2D) and one dimensional (1D) mapping. Results A significant association between normalised difference vegetation index (NDVI) and abundance of Bulinus spp. was detected (log risk ratio − 0.83, 95% CrI − 1.57, − 0.09). A qualitatively similar association was found between NDVI and Biomphalaria sp. but was not statistically significant (log risk ratio − 1.42, 95% CrI − 3.09, 0.10). Analyses of all other environmental data were considered non-significant. Conclusions The spatial range in which interpolation of snail distributions is possible appears < 10km owing to fine-scale biotic and abiotic heterogeneities. The forthcoming challenge is to refine geospatial sampling frameworks with future opportunities to map schistosomiasis within actual or predicted snail distributions. In so doing, this would better reveal local environmental transmission possibilities. Graphical Abstract

Background: Along the southern shoreline of Lake Malawi, the incidence of schistosomiasis is increasing with snails of the genera Bulinus and Biomphalaria transmitting urogenital and intestinal schistosomiasis, respectively. Since the underlying distribution of snails is partially known, often being focal, developing pragmatic spatial models that interpolate snail information across under-sampled regions is required to understand and assess current and future risk of schistosomiasis. Methods: A secondary geospatial analysis of recently collected malacological and environmental survey data was undertaken. Using a Bayesian Poisson latent Gaussian process model, abundance data were fitted for Bulinus and Biomphalaria. Interpolating the abundance of snails along the shoreline (given their relative distance along the shoreline) was achieved by smoothing, using extracted environmental rainfall, land surface temperature (LST), evapotranspiration, normalised difference vegetation index (NDVI) and soil type covariate data for all predicted locations. Our adopted model used a combination of two-dimensional (2D) and one dimensional (1D) mapping. Results: A significant association between normalised difference vegetation index (NDVI) and abundance of Bulinus spp. was detected (log risk ratio − 0.83, 95% CrI − 1.57, − 0.09). A qualitatively similar association was found between NDVI and Biomphalaria sp. but was not statistically significant (log risk ratio − 1.42, 95% CrI − 3.09, 0.10). Analyses of all other environmental data were considered non-significant. Conclusions: The spatial range in which interpolation of snail distributions is possible appears < 10km owing to fine-scale biotic and abiotic heterogeneities. The forthcoming challenge is to refine geospatial sampling frameworks with future opportunities to map schistosomiasis within actual or predicted snail distributions. In so doing, this would better reveal local environmental transmission possibilities. [ABSTRACT FROM AUTHOR]

Abstract The three most important genera of snails for the transmission of schistosomes are Bulinus, Biomphalaria and Oncomelania. Each of these genera, found in two distantly related families, includes species that act as the intermediate host for one of the three most widespread schistosome species infecting humans, Schistosoma haematobium, S. mansoni and S. japonicum, respectively. An important step in the fight against schistosomiasis in Asia has been taken with the publication of the article “Chromosome-level genome assembly of Oncomelania hupensis: the intermediate snail host of Schistosoma japonicum”, which means that genomes for all three major genera, including species across three continents, are now available in the public domain. This includes the first genomes of African snail vectors, namely Biomphalaria sudanica, Bi. pfeifferi and Bulinus truncatus, as well as high-quality chromosome level assemblies for South American Bi. glabrata. Most importantly, the wealth of new genomic and transcriptomic data is helping to establish the specific molecular mechanisms that underly compatibility between snails and their schistosomes, which although diverse and complex, may help to identify potential targets dictating host parasite interactions that can be utilised in future transmission control strategies. This new work on Oncomelania hupensis and indeed studies on other snail vectors, which provide deep insights into the genome, will stimulate research that may well lead to new and much needed control interventions. Graphical Abstract

The three most important genera of snails for the transmission of schistosomes are Bulinus, Biomphalaria and Oncomelania. Each of these genera, found in two distantly related families, includes species that act as the intermediate host for one of the three most widespread schistosome species infecting humans, Schistosoma haematobium, S. mansoni and S. japonicum, respectively. An important step in the fight against schistosomiasis in Asia has been taken with the publication of the article "Chromosome-level genome assembly of Oncomelania hupensis: the intermediate snail host of Schistosoma japonicum", which means that genomes for all three major genera, including species across three continents, are now available in the public domain. This includes the first genomes of African snail vectors, namely Biomphalaria sudanica, Bi. pfeifferi and Bulinus truncatus, as well as high-quality chromosome level assemblies for South American Bi. glabrata. Most importantly, the wealth of new genomic and transcriptomic data is helping to establish the specific molecular mechanisms that underly compatibility between snails and their schistosomes, which although diverse and complex, may help to identify potential targets dictating host parasite interactions that can be utilised in future transmission control strategies. This new work on Oncomelania hupensis and indeed studies on other snail vectors, which provide deep insights into the genome, will stimulate research that may well lead to new and much needed control interventions. [ABSTRACT FROM AUTHOR]

Many rivers and streams in Nigeria are habitats of freshwater snails. Many of these snails are edible, whereas others are intermediate hosts of various flatworms. Nine rivers and streams from three towns in Ekiti State, Nigeria, were examined for the presence of freshwater snails. Each freshwater habitat was sampled for snails at the designated sites for 15 min on a monthly basis using a 0.2 mm mesh scoop. The collected snails were transported to the laboratory in pre-labelled plastic containers. Two thousand three hundred and thirty-one (2331) freshwater snails were collected from all habitats. Lanistes libycus had the highest population, 1044 (44.8%). The other species were Melanoides tuberculata 550 (23.6%), Bulinus globosus 401 (17.2%), and Potadoma moerchi 336 (14.4%). Freshwater snails were more abundant at the beginning of the rainy season (March-May) than during heavy rainfall (July-October). The environmental conditions of the study area supported the occurrence of these snail species. Although some species of these snails are edible, others can serve as intermediate hosts for parasitic flatworms, which requires urgent attention. [ABSTRACT FROM AUTHOR]

Different populations of hosts and parasites experience distinct seasonality in environmental factors, depending on local-scale biotic and abiotic factors. This can lead to highly heterogeneous disease outcomes across host ranges. Variable seasonality characterizes urogenital schistosomiasis, a neglected tropical disease caused by parasitic trematodes (Schistosoma haematobium). Their intermediate hosts are aquatic Bulinus snails that are highly adapted to extreme rainfall seasonality, undergoing prolonged dormancy yearly. While Bulinus snails have a remarkable capacity for rebounding following dormancy, we investigated the extent to which parasite survival within snails is diminished. We conducted an investigation of seasonal snail schistosome dynamics in 109 ponds of variable ephemerality in Tanzania from August 2021 to July 2022. First, we found that ponds have two synchronized peaks of schistosome infection prevalence and observed cercariae, though of lower magnitude in the fully desiccating than non-desiccating ponds. Second, we evaluated total yearly schistosome prevalence across an ephemerality gradient, finding ponds with intermediate ephemerality to have the highest infection rates. We also investigated dynamics of non-schistosome trematodes, which lacked synonymity with schistosome patterns. We found peak schistosome transmission risk at intermediate pond ephemerality, thus the impacts of anticipated increases in landscape desiccation could result in increases or decreases in transmission risk with global change. [ABSTRACT FROM AUTHOR]

Bulinus snails surviving drought play a key role in the seasonal transmission of urogenital schistosomiasis, although our knowledge of their adaptation to dry season is still limited. We investigated the survival dynamic and infestation by the Schistosoma haematobium of Bulinus snails during the dry and rainy seasons in a single pond in an area of seasonal schistosomiasis transmission in Senegal. During the rainy season, 98 (94.23%) B. senegalensis and six (5.76%) B. umbilicatus were collected, respectively. In the dry season, B. umbilicatus outnumbered B. senegalensis, but all five (100%) B. senegalensis collected were viable and alive after the interruption of aestivation by immersion in water, while only 7 of 24 (29.16%) B. umbilicatus collected emerged from their dormant state. The rate of infestation with S. haeamatobium during the rainy season was 18.2% (19/104), while all the viable snails collected during the dry season were negative. B. senegalensis and B. umbilicatus have different seasonal dynamics with no evidence of maintaining S. haematobium infestation during the drought. Further studies including more survey sites and taking account both snails biology and ecological conditions are needed to better understand snail adaptation to seasonal changes and their ability to maintain S. haeamatobium infestation during drought.

The measurement and analysis of snail biometrics help to identify and differentiate species, study their growth, and understand their ecological relationships. The growth pattern, DNA yield and purity of Bulinus. globosus from River Wudil, Kano State, were investigated using standard methods. The mean ranges in mm and g from 7.9±2.9, 5.7±2.5, 4.8±1.8, 3.4±1.2, 1.5±0.2, 1.6±0.0, 2.4±0.2, 1.2±0.1, 1.4±0.1, 65.8±1.9 and 22.2±0.4 were recorded for length, width, aperture height, aperture width, height width ratio, height and aperture height ratio, height and aperture width ratio, width and aperture height ratio, aperture height and aperture width ratio, shell weight and flesh weight respectively. About 33.7 % of weight of the snail is made up of flesh by weight. The regression coefficient "b" showed that B. globosus exhibited a negative allometric growth pattern while the correlation coefficient (r) in all the shell parameters were below 1, indicating a weak correlation between the parameters. Mean DNA yield and purity were 120.03 ± 5.10 ng/µl and 1.81 ± 1.21. It is concluded that the freshwater snail, B. globusus from River Wudil exhibits negative allometric growth pattern and its DNA yield is well above the minimum standard (A260/A280 ratio of 1.7-2.0) while the pure extracts are good enough for further molecular study. [ABSTRACT FROM AUTHOR]

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

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.

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. [ABSTRACT FROM AUTHOR]

Some species of freshwater snails are known to be intermediate hosts of biomedical importance. This study was conducted to identify some physico-chemical parameters of water bodies associated with the distribution of freshwater snail species in the Federal Capital Territory, Abuja. Eight water bodies in four locations were surveyed for the presence of freshwater snails. Five physico chemical parameters (pH, temperature, dissolved oxygen content, salinity and water speed) were measured using standard water meters. A correlation matrix between the water parameters and the snail species were analysed. A total of 1,225 freshwater snails belonging to eight species and families were collected in the study area. These were Bulinus truncatus 304 (24.8%), B. umbilicatus 162 (13.2%), B. globosus 138 (11.3%), Biomphalaria pfeifferi 138 (11.3%), Aplexa waterloti 190 (15.5%), Physa acuta 96 (7.8%), Lymnea natalensis (15.8%). and Melanoides tuberculata 3 (0.2%). Three of these snail species {B. globosus, B. Pfeffeiri and L. natalensis} which are known intermediate hosts of schistosomes were reasonably present in the study area. Out of the five water parameters investigated, two (Dissolved oxygen content and salinity) were found to significantly associated with the distribution of freshwater snail species in the area (P<0.05). The study recommends freshwater snail control intervention to interrupt the transmission and spread of human and animal diseases in the area. [ABSTRACT FROM AUTHOR]

Abstract Background Sound knowledge of the abundance and distribution of intermediate host snails is key to understanding schistosomiasis transmission and to inform effective interventions in endemic areas. Methods A longitudinal field survey of freshwater snails of biomedical importance was undertaken in the Niger River Valley (NRV) between July 2011 and January 2016, targeting Bulinus spp. and Biomphalaria pfeifferi (intermediate hosts of Schistosoma spp.), and Radix natalensis (intermediate host of Fasciola spp.). Monthly snail collections were carried out in 92 sites, near 20 localities endemic for S. haematobium. All bulinids and Bi. pfeifferi were inspected for infection with Schistosoma spp., and R. natalensis for infection with Fasciola spp. Results Bulinus truncatus was the most abundant species found, followed by Bulinus forskalii, R. natalensis and Bi. pfeifferi. High abundance was associated with irrigation canals for all species with highest numbers of Bulinus spp. and R. natalensis. Seasonality in abundance was statistically significant in all species, with greater numbers associated with dry season months in the first half of the year. Both B. truncatus and R. natalensis showed a negative association with some wet season months, particularly August. Prevalences of Schistosoma spp. within snails across the entire study were as follows: Bi. pfeifferi: 3.45% (79/2290); B. truncatus: 0.8% (342/42,500); and B. forskalii: 0.2% (24/11,989). No R. natalensis (n = 2530) were infected. Seasonality of infection was evident for B. truncatus, with highest proportions shedding in the middle of the dry season and lowest in the rainy season, and month being a significant predictor of infection. Bulinus spp. and Bi. pfeifferi showed a significant correlation of snail abundance with the number of snails shedding. In B. truncatus, both prevalence of Schistosoma spp. infection, and abundance of shedding snails were significantly higher in pond habitats than in irrigation canals. Conclusions Evidence of seasonality in both overall snail abundance and infection with Schistosoma spp. in B. truncatus, the main intermediate host in the region, has significant implications for monitoring and interrupting transmission of Schistosoma spp. in the NRV. Monthly longitudinal surveys, representing intensive sampling effort have provided the resolution needed to ascertain both temporal and spatial trends in this study. These data can inform planning of interventions and treatment within the region.

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. [ABSTRACT FROM AUTHOR]

Schistosomiasis is a tropical parasitic disease affecting more than 200 million people worldwide, predominantly in Africa. The World Health Organization recently highlighted the importance of targeted control of the freshwater snails acting as intermediate hosts for the parasites causing schistosomiasis. However, because of a shortage of trained experts and resources, detailed information on spatiotemporal snail distributions, which is needed for targeted control measures, is often missing. We explore the potential of citizen science to build these much-needed datasets through fine-grained, frequent snail sampling. We trained a network of 25 citizen scientists to weekly report on snail host abundances in 77 predefined water contact sites in and around Lake Albert (western Uganda). Snail abundance, together with marked GPS locations, water chemistry parameters, and photographs of the identified snails are recorded and submitted using the freely available mobile phone application KoBoToolbox. Trained researchers then engage in remote, semi-automatic validation of the submissions, after which there is an opportunity to provide targeted feedback to the citizen scientists. Five months after the operationalisation of the network, a total of 570 reports were submitted and personalized feedback was given, resulting in lasting improvements in subsequent reporting and snail genus identification. The preliminary results show the possibility of citizen science to independently obtain reliable data on the presence of schistosome snail hosts. We therefore argue that citizen-driven monitoring on a high spatiotemporal resolution could help to generate the much-needed data to support local targeted snail control measures in remote and/or resource-limited environments. [ABSTRACT FROM AUTHOR]

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 Biomphalaria pfeifferi, and Bulinus globosus snails under laboratory conditions. For B. pfeifferi, we tested seed extracts on juvenile and adult snails while only adult B. globosus were available for testing. Snails were exposed to water and crude ethanol extracts for 72 h and significant concentrationdependent mortality rates were observed. The number of B. pfeifferi juveniles collected was not enough for a comprehensive investigation against both solvents. We, therefore, tested them against water extracts only. A lethal concentration of 0.02 mg/mL killed 50% of the snails (LC50) for both water and ethanol extracts on adult B. pfeifferi snails. Our results suggest that pumpkin seed extracts have a significant molluscicidal effect on B. pfeifferi and B. globosus snails. The LC50 values for all the extracts in B. pfeifferi and B. globosus snails are within the threshold set for potential molluscicides by the World Health Organisation. We propose that C.maxima seed extracts be considered as potential molluscicidal agents in Schistosomiasis transmission control. [ABSTRACT FROM AUTHOR]

Bulinus snails surviving drought play a key role in the seasonal transmission of urogenital schistosomiasis, although our knowledge of their adaptation to dry season is still limited. We investigated the survival dynamic and infestation by the Schistosoma haematobium of Bulinus snails during the dry and rainy seasons in a single pond in an area of seasonal schistosomiasis transmission in Senegal. During the rainy season, 98 (94.23%) B. senegalensis and six (5.76%) B. umbilicatus were collected, respectively. In the dry season, B. umbilicatus outnumbered B. senegalensis , but all five (100%) B. senegalensis collected were viable and alive after the interruption of aestivation by immersion in water, while only 7 of 24 (29.16%) B. umbilicatus collected emerged from their dormant state. The rate of infestation with S. haeamatobium during the rainy season was 18.2% (19/104), while all the viable snails collected during the dry season were negative. B. senegalensis and B. umbilicatus have different seasonal dynamics with no evidence of maintaining S. haematobium infestation during the drought. Further studies including more survey sites and taking account both snails biology and ecological conditions are needed to better understand snail adaptation to seasonal changes and their ability to maintain S. haeamatobium infestation during drought.

Schistosomiasis is a snail-borne disease that has a considerable impact on human and animal health, particularly in sub-Saharan Africa. The intermediate hosts of the schistosome parasites are freshwater snails of the genera Biomphalaria Preston, 1910 and Bulinus Müller, 1781. In order to identify existing gaps in the spread of the disease in the Democratic Republic of Congo (DRC), this study compiled the available knowledge of the distribution, population dynamics and ecology of the intermediate hosts of schistosomiasis. A systematic literature search was conducted in PubMed, Embase and Scopus for all malacological studies on schistosoma intermediate hosts in DRC published between 1927 and October 2022. A total of 55 records were found, of which 31 met the inclusion criteria: these were published field and experimental studies conducted in the DRC and focused on snails as intermediate hosts of schistosomes. The analysis of these studies revealed that more up-to-date data on the distribution of snail intermediate hosts in the DRC are needed. Moreover, ecological factors have been less studied for Bulinus species than for Biomphalaria species. These factors play a crucial role in determining suitable snail habitats, and the lack of comprehensive information poses a challenge in snail control. This review makes it clear that there are no current malacological data in the DRC. There is a clear need for molecular and ecological research to update the exact species status and population dynamics of all potential intermediate host species. This will facilitate targeted snail control measures that complement drug treatment in the control of schistosomiasis in the country.

Introduction: Schistosomiasis and fasciolosis are snail-borne diseases of great medical and veterinary health importance. The World Health Organization recommends complementing drug treatment with snail control and community involvement for disease elimination, but there is a general lack of snail experts and hence snail distribution data. Therefore, we adopted a citizen science approach and involved citizens in the monitoring of medically and veterinary important snail taxa., Materials and Methods: Snail data was collected weekly by 25 trained citizen scientists (CSs) at 76 sites around southern Lake Albert (Uganda) for 20 months. At each site, snails were searched for 30 minutes, sorted, target snail hosts identified to genus level, counted and data submitted through a smartphone application. The quality of this data was assessed by comparing it to monthly data collected by an 'expert' malacologist using the same sampling protocol. Generalised binomial logistic and linear mixed-effects models were used to analyse the variables for agreement between the CSs and expert., Findings: The binary agreement in presence/absence of Biomphalaria, Bulinus and Radix snails reported by the expert and CSs ranged between 70% and 86% (900 reports) with an average of 17% false negatives (sites wrongly defined as snail-free). The agreement for Biomphalaria and Radix increased with snail abundance, and false negatives decreased when the number of snails collected by citizens was aggregated per month. Site type significantly predicted binary agreement, which was lowest at lake sites (55%) and highest at spring sites (99%) with variations across genera. Similar temporal trends in snail abundance were recorded despite the expert reporting higher abundance. However, the relative abundance was consistent across site types. The match between the sites with highest Biomphalaria spp. abundance identified by CSs and expert was consistently high (~84.1%) and increased over time., Conclusions and Recommendations: Our results demonstrate the potential of citizen science to map putative schistosomiasis transmission sites. We therefore argue that this inclusive, powerful and cost-effective approach can be more sustainable than top-down monitoring and intervention campaigns., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2024 Tumusiime et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Background: The construction of Lake Kariba brought about a rise in the incidence of schistosomiasis in its surrounding towns of Kariba (Zimbabwe) and Siavonga (Zambia). After extensive control programs in Kariba, schistosomiasis prevalence dropped significantly. The objective of this study was to revisit the same localities sampled by Chimbari et al. (2003), and provide an update on the snail community and prevalence of trematodes in the Northern shore of Lake Kariba while focusing on planorbid species., Methods: Monthly sampling of snails at 16 sites along the Northern shoreline of Lake Kariba, near Kariba town, was undertaken for one year. Minimum one specimen per morphotype was identified using molecular barcoding (sequencing a fragment of cytochrome c oxidase I subunit (COI)). The infection status of snails was assessed by Rapid Diagnostic PCRs (RD-PCR), and trematode infections were genotyped by sequencing COI and 18S rDNA markers., Results: We collected and identified seven snail species: Bulinus truncatus, Bulinus forskalii, Gyraulus sp., Physella acuta, Bellamya sp., Radix affinis plicatula and Pseudosuccinea columella. Physella acuta was the most abundant snail species (comprising 56.95% of the total snail count) and present at all sites. The B. truncatus population was found to be infected with the stomach fluke Carmyerius cruciformis, a Petasiger sp. and a trematode species belonging to the family Notocotylidae. No Schistosoma sp. infections were detected in our collected snail specimens., Conclusions: We report B. truncatus as an intermediate snail host for Carmyerius cruciformis, and the presence of three non-schistosome trematode species that have not been reported in Lake Kariba before. Furthermore, we detect a possible shift in the snail community when compared to the report by Chimbari et al. (2003): this is the first record of Gyraulus sp. in Lake Kariba, and we did not observe the previously reported B. pfeifferi, B. globosus and Radix natalensis. Although this shift in snail communities might have contributed to the absence of Schistosoma spp. detection in this study, further monitoring of final and intermediate hosts across the Kariba basin is essential to prove a decrease of schistosomiasis in the area., Competing Interests: Declaration of Competing Interest The authors declare that they have no competing interests., (Copyright © 2023. Published by Elsevier B.V.)

Abstract 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.

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<0.05). The difference in snail abundance across habitat was not significant (F=0.525, p= 0.873). DO was the significant parameter influencing abundance of snail host identified. It is concluded that malacological survey is therefore vital for surveillance and effective snail control programme. [ABSTRACT FROM AUTHOR]

Objective: This research was conducted to determine the influence of physico-chemical characteristics on diversity of the intermediate host of schistosomes in Makwaye and Kubanni reservoirs, Zaria, Nigeria. Materials and methods: Physico-chemical characteristics and diversity of the intermediate host of schistosomes in Makwaye and Kubanni reservoirs, Zaria, Nigeria, were investigated for a 12-month period (January to December, 2014). Physico-chemical properties were analyzed according to the standard procedures for examination of water and waste waters. The molluscs were collected using an Ekman grab model number 923, measuring 19 cm by 14 cm with an area of 0.0266 m2. PAST software was used to run Principal Component Analysis, Shanon-Weiner diversity index and Cluster analysis. Results: A total of 978 Bulinus globosus and 3612 Biomphalaria pfefferi were recorded in Makwaye reservoir with high abundance in dry season while a total of 163 B. globosus and 602 B. pfefferi was recorded in Kubanni reservoir with higher abundance in wet season. Shanon-Weiner diversity index of Makwaye reservoir also ranged from 2.01-2.22 and 1.16-1.31 in Kubanni reservoir. Significant variations (P≤0.05) were observed in physicochemical parameters, schistosomes intermediate host abundance with seasons. Principal Component Analysis (PCA) revealed significant influence (P≤0.05) of physicochemical properties on schistosome intermediate host composition, with BOD, DO, pH and Calcium significantly influencing the presence of B. globosus and B. pfefferi in both reservoirs. Conclusion: It is concluded that the presence of these molluscs in the study areas may constitute a predisposing factor to schistosomiasis and therefore, various management strategies and recommend preventive measures to people coming in contact with these two reservoirs. [J Adv Vet Anim Res 2017; 4(4.000): 363-370]

Background: Freshwater snails of the genera Bulinus spp., Biomphalaria spp., and Oncomelania spp. are the main intermediate hosts of human and animal schistosomiasis. Identification of these snails has long been based on morphological and/or genomic criteria, which have their limitations. These limitations include a lack of precision for the morphological tool and cost and time for the DNA-based approach. Recently, Matrix-Assisted Laser Desorption/Ionization Time-Of-Flight (MALDI-TOF) mass spectrometry, a new tool used which is routinely in clinical microbiology, has emerged in the field of malacology for the identification of freshwater snails. This study aimed to evaluate the ability of MALDI-TOF MS to identify Biomphalaria pfeifferi and Bulinus forskalii snail populations according to their geographical origin., Methods: This study was conducted on 101 Bi. pfeifferi and 81 Bu. forskalii snails collected in three distinct geographical areas of Senegal (the North-East, South-East and central part of the country), and supplemented with wild and laboratory strains. Specimens which had previously been morphologically described were identified by MALDI-TOF MS [identification log score values (LSV) ≥ 1.7], after an initial blind test using the pre-existing database. After DNA-based identification, new reference spectra of Bi. pfeifferi (n = 10) and Bu. forskalii (n = 5) from the geographical areas were added to the MALDI-TOF spectral database. The final blind test against this updated database was performed to assess identification at the geographic source level., Results: MALDI-TOF MS correctly identified 92.1% of 101 Bi. pfeifferi snails and 98.8% of 81 Bu. forskalii snails. At the final blind test, 88% of 166 specimens were correctly identified according to both their species and sampling site, with LSVs ranging from 1.74 to 2.70. The geographical source was adequately identified in 90.1% of 91 Bi. pfeifferi and 85.3% of 75 Bu. forskalii samples., Conclusions: Our findings demonstrate that MALDI-TOF MS can identify and differentiate snail populations according to geographical origin. It outperforms the current DNA-based approaches in discriminating laboratory from wild strains. This inexpensive high-throughput approach is likely to further revolutionise epidemiological studies in areas which are endemic for schistosomiasis., (© 2024. The Author(s).)

Schistosomiasis, the second largest parasitic disease in the world after malaria, poses a significant threat to human health and causes public health issues. The disease primarily affects populations in economically underdeveloped tropical regions, earning it the title of "neglected tropical disease". Schistosomiasis is difficult to eradicate globally if medication alone is used. One of the essential elements of thorough schistosomiasis prevention and control is the management and disruption of the life cycle of intermediate host snails. The key approach to controlling the transmission of schistosomiasis is to control the intermediate hosts of the schistosome to disrupt its life cycle. We believe that approaching it from the perspective of the intermediate host's immunity could be an environmentally friendly and potentially effective method. Currently, globally significant intermediate host snails for schistosomes include Oncomelania hupensis, Biomphalaria glabrata, and Bulinus truncatus. The immune interaction research between B. glabrata and Schistosoma mansoni has a history of several decades, and the complete genome sequencing of both B. glabrata and B. truncatus has been accomplished. We have summarized the immune-related factors and research progress primarily studied in B. glabrata and B. truncatus and compared them with several humoral immune factors that O. hupensis research focuses on: macrophage migration inhibitory factor (MIF), Toll-like receptors (TLRs), and thioredoxin (Trx). We believe that continued exploration of the immune interactions between O. hupensis and Schistosoma japonicum is valuable. This comparative analysis can provide some direction and clues for further in-depth research. Comparative immunological studies between them not only expand our understanding of the immune defense responses of snails that act as intermediaries for schistosomes but also facilitate the development of more comprehensive and integrated strategies for schistosomiasis prevention and control. Furthermore, it offers an excellent opportunity to study the immune system of gastropods and their co-evolution with pathogenic organisms., (© 2023. The Author(s).)

Effect of lupine extracts nanoparticles (NPs) coated with copper sulphate on the mortality and eggs productivity of aquatic snails, Biomphalaria alexandrina Ehrenberg and Bulinus truncatus Audouin, and terrestrial snail, Eobania vermiculata Müller, were investigated in comparison with copper sulphate nanoparticles and both treatments compare with untreated group in the present and previous investigation. This experiment was planned to elucidate the molluscicidal properties of lupine extract coated with CuSO4 NPs against adult B. alexandrina B. truncatus and E. vermiculata snails after 24 hours exposure, in dark conditions, followed by another 48 hrs. light for recovery. The results revealed that lupine extracts nanoparticles has more effect than copper sulphate nanoparticles on both aquatic or terrestrial snail mortality. It caused 100% mortality for B. alexandrina and B. truncates, at concentration of 20 ppm, after 24 hours of exposure in dark followed by 48 hours recovery in day light. Copper sulphate nanoparticles at the same concentration caused only 70% and 46. 67% mortality for B. alexandrina and B. truncates, respectively, under the same conditions. Mortality rate increased with the increase of concentrations either in lupine NPs or CuO4 NPs. On normal lupine extract the concentration that caused 100% mortality was equal to ten folds of lupine NPs. Egg productivity of the healthy thirty individuals, of B. alexandrina, B. truncatus and E. vermiculata, were investigated and compared with the survival snails in low concentrations of both Cu NPs and lupine NPs, to study the effect of nanoparticle materials on the snail fecundity. Both lupine extract nanoparticles and copper sulphate nanoparticles may have a sterilized effect, where B. alexandrina and B. truncatus snails exposed to sub lethal doses from them didn't laid any egg masses after treatment. E. vermiculata, treated or untreated individuals, didn't laid any eggs either, because it had a specific season of reproduction which not coinciding with the time of experiment. [ABSTRACT FROM AUTHOR]

This study was carried out to provide information on the population dynamics of the snail intermediate host of Schistosoma spp., in Abuja. A cross-sectional study was carried out on water bodies with high human contact activities in all the six area councils in Federal Capital Territory including; Narachi, Rafir shawa, Shetiko, Ushafa, Yangoji and Basa Rivers in Abaji, Gwagwalada, Kuje, Bwari, Kwali and Abuja Municipal Area Council respectively. Sampling of snail was based on convenience and presence of snail in the selected areas. Each settlement in the sample population was visited once monthly between March and September, 2017 for snail sample collection. A total of 766 fresh water snails identified to be snail intermediate hosts of schistosomiasis were collected during the study. The prevalence of fresh water snail intermediate hosts of Schistosoma spp., in Abuja comprises 30.16% Bulinus globosus, 11.75% of Bulinus truncatus and 58.09% of Biomphilaria pfeifferi. These fresh water snails were found to be more prevalent in the month of March in all the Local Government Area Council sampled with Gwagwalada Area Council having the highest prevalence of fresh water snail while Bwari Area Council had the lowest. This study revealed that there was high prevalence of snail intermediate hosts of schistosomiasis in Abuja. Hence, there is need for appropriate intervention by the Federal Ministry of Health (FMOH), in collaboration with the National Schistosomiasis Control Program (NSCP) to control snail intermediate hosts of Schistosomes spp., in the study-area using chemical or biological molluscide. [ABSTRACT FROM AUTHOR]

The article offers information on the bioactivity of co-ArNp on Schistosoma haematobium and its snail vector Bulinus truncatus. It mentions 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; and also mentions treatment of Schistosoma haematobium reduced worm motility.

This study accessed the dynamics of urogenital schistosomiasis transmission in Nkalagu Community. A total of 500 mid-day urine samples were collected and transported to Microbiology Laboratory, Ebonyi State University, for analysis. 10ml each of the urine samples was centrifuged at 2500 rpm for 5 minutes. Transmission potential of snail intermediate host of Schistosomes collected from different sampling station at the transmission sites within the study community was equally accessed. The snail species collected were placed individually into a clean beaker with little quantity of water and then subjected to shedding light for 2 hours. Data obtained were entered in excel spread sheet and analyzed using chi square test. The result obtained shows that 205 (41%) out of 500 individuals examined were excreting S. haematobium ova in their urine. The highest prevalence of infection (23%) was found among 11-20-year age groups. Males were more infected (25.4%) than their female counterparts (15.6%), although this was not statistically significant (p > 0.05). A total of 283 snails belonging to two Bulinus species (B. globosus and B. truncatus) were collected from the four sites sampled. Bulinus globosus recorded the highest species abundance (177) with the highest occurrence in site A. 52 (18.4%) out of 283 snails collected were infected with cercariae, and the highest cercariae infection (12.0%) was recorded among B. globosus. With prevalence of 41% among the human population and the prevalence of 18.4% patent infection among the snail intermediate hosts, urogenital schistosomiasis is still a public health problem in the study area and falls within the WHO classification of endemic area. Public health campaign is recommended in order to educate the people on the mode of transmission and control of the disease. [ABSTRACT FROM AUTHOR]

Schistosomiasis is a vector-borne disease transmitted by freshwater snails and is prevalent in rural areas with poor sanitation and no access to tap water. Three snail species are known to transmit schistosomiasis in South Africa (SA), namely Biomphalaria pfeifferi, Bulinus globosus and Bulinus africanus. In 2003, a predicted prevalence of 70% was reported in tropical climates in SA. Temperature and rainfall variability can alter schistosomiasis-transmitting snails' development by increasing or decreasing their abundance and geographical distribution. This study aimed to map the historical distribution of schistosomiasis from 1950 to 2006 in SA. The snail sampling data were obtained from the historical National Snail Freshwater Collection (NFSC). Bioclimatic variables were extracted using ERA 5 reanalysis data provided by the Copernicus Climate Change Service. In this study, we used 19 bioclimatic and four soil variables. The temporal aggregation was the mean climatological period pre-calculated over the 40-year reference period with a spatial resolution of 0.5° x 0.5°. Multicollinearity was reduced by calculating the Variance Inflation Factor Core (VIF), and highly correlated variables (> 0.85) were excluded. To obtain an "ensemble" and avoid the integration of weak models, we averaged predictions using the True Skill Statistical (TSS) method. Results showed that the ensemble model achieved the highest Area Under the Curve (AUC) scores (0.99). For B. africanus, precipitation-related variables contributed to determining the suitability for schistosomiasis. Temperature and precipitation-related variables influenced the distribution of B. globosus in all three models. Biomphalaria pfeifferi showed that Temperature Seasonality (bio4) contributed the most (47%) in all three models. According to the models, suitable areas for transmitting schistosomiasis were in the eastern regions of South Africa. Temperature and rainfall can impact the transmission and distribution of schistosomiasis in SA. The results will enable us to develop future projections for Schistosoma in SA based on climate scenarios., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2023 Ayob et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Urogenital schistosomiasis (UGS) caused by Schistosoma haematobium is endemic in the South West Region of Cameroon. An understanding of the abundance and distribution of the Bulinus snail, intermediate host can inform strategic snail control programmes at a local scale. This study investigated seasonal dynamics and environmental factors influencing occurrence and abundance of freshwater snail intermediate hosts in Tiko, a semi-urban endemic focus in the Mount Cameroon area. A longitudinal malacological field survey was conducted between December 2019 and December 2020 in the Tiko municipality. Snails were collected for one year monthly at 12 different human water contact sites along a stretch of the Ndongo stream using a standardized sampling technique. Freshwater snails were identified using shell morphological features. In addition, water temperature, pH, electrical conductivity, total dissolved solutes, salinity, water depth, width and flow velocity were measured, and vegetation cover as well as substrate type were determined. Bayesian regression models were used to identify the main environmental factors affecting the occurrence and abundance of Bulinus intermediate host. In total, 2129 fresh water snails were collected during the study period. Physa (51.4%) was the most abundant genus followed by Melanoides (28.6%) then, Bulinus (15.5%), Lymnaea (4.2%), Indoplanorbis (0.2%) and Potadoma (0.1%). Seasonality in abundance was significant in Bulinus sp as well as other genera, with greater numbers in the dry season (peaks between December and February). Water temperature, a rocky or sandy substrate type associated positively with Bulinus sp, meanwhile a higher water flow rate and medium vegetation negatively influenced the snail intermediate host population. These findings underscore the importance of timing behavioural and snail control interventions against schistosomiasis as well as increase vigilance of other trematode diseases in the study area. The continuous spread of planorbid snail hosts is a major concern., Competing Interests: The authors have declared that no have competing interests exist., (Copyright: © 2023 Wepnje et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Abstract Introduction Schistosomiasis remains an important public health problem that undermines social and economic development in tropical regions of the world, mainly Sub-Saharan Africa. We are not aware of any systematic review of the literature of the epidemiology and transmission of schistosomiasis in Malawi since 1985. Therefore, we reviewed the current state of knowledge of schistosomiasis epidemiology and transmission in this country and identified knowledge gaps and relevant areas for future research and research governance. Methods We conducted computer-aided literature searches of Medline, SCOPUS and Google Scholar using the keywords: “schistosomiasis”, “Bilharzia”, “Bulinus” and “Biomphalaria” in combination with “Malawi”. These searches were supplemented by iterative reviews of reference lists for relevant publications in peer reviewed international scientific journals or other media. The recovered documents were reviewed for their year of publication, location of field or laboratory work, authorship characteristics, ethics review, funding sources as well as their findings regarding parasite and intermediate host species, environmental aspects, geographical distribution, seasonality of transmission, and infection prevalence and intensities. Review A total of 89 documents satisfied the inclusion criteria and were reviewed. Of these, 76 were published in international scientific journals, 68 were peer reviewed and 54 were original research studies. Most of the documents addressed urinary schistosomiasis and about two thirds of them dealt with the definitive host. Few documents addressed the parasites and the intermediate hosts. While urinary schistosomiasis occurs in most parts of Malawi, intestinal schistosomiasis mainly occurs in the central and southern highlands, Likoma Island and Lower Shire. Studies in selected communities estimated prevalence rates of up to 94.9% for Schistosoma haematobium and up to 67.0% for Schistosoma mansoni with considerable geographical variation. The main intermediate host species are Bulinus globosus and Bulinus nyassanus for urinary schistosomiasis and Biomphalaria pfeifferi for intestinal schistosomiasis. Seasonality of transmission tends to vary according to geographical, environmental, biological and behavioural factors. Conclusion Transmission of schistosomiasis in Malawi appears to be highly focal, with considerable variation in space and time. Many locations have not been covered by epidemiological investigations and, thus, information on the transmission of schistosomiasis in Malawi remains fragmented. Functional infection risk assessment systems based on systematic investigations and surveillance are required for developing informed prevention and control strategies.

Objective: This research was conducted to determine the influence of physicochemical characteristics on diversity of the intermediate host of schistosomes in Makwaye and Kubanni reservoirs, Zaria, Nigeria. Materials and methods: Physico-chemical characteristics and diversity of the intermediate host of schistosomes in Makwaye and Kubanni reservoirs, Zaria, Nigeria, were investigated for a 12-month period (January to December, 2014). Physico-chemical properties were analyzed according to the standard procedures for examination of water and waste waters. The molluscs were collected using an Ekman grab model number 923, measuring 19 cm by 14 cm with an area of 0.0266 m2. PAST software was used to run Principal Component Analysis, Shanon-Weiner diversity index and Cluster analysis. Results: A total of 978 Bulinus globosus and 3612 Biomphalaria pfefferi were recorded in Makwaye reservoir with high abundance in dry season while a total of 163 B. globosus and 602 B. pfefferi was recorded in Kubanni reservoir with higher abundance in wet season. Shanon-Weiner diversity index of Makwaye reservoir also ranged from 2.01-2.22 and 1.16-1.31 in Kubanni reservoir. Significant variations (P=0.05) were observed in physicochemical parameters, schistosomes intermediate host abundance with seasons. Principal Component Analysis (PCA) revealed significant influence (P=0.05) of physicochemical properties on schistosome intermediate host composition, with BOD, DO, pH and Calcium significantly influencing the presence of B. globosus and B. pfefferi in both reservoirs. Conclusion: It is concluded that the presence of these molluscs in the study areas may constitute a predisposing factor to schistosomiasis and therefore, various management strategies and recommend preventive measures to people coming in contact with these two reservoirs. [ABSTRACT FROM AUTHOR]