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1. Land use impacts on parasitic infection: a cross-sectional epidemiological study on the role of irrigated agriculture in schistosome infection in a dammed landscape

   https://doi.org/10.1186/s40249-021-00816-5  

   Lund, Andrea J.; Rehkopf, David H.; Sokolow, Susanne H.; Sam, M. Moustapha; Jouanard, Nicolas; Schacht, Anne-Marie; Senghor, Simon; Fall, Assane; Riveau, Gilles; De Leo, Giulio A.; et al (December 2021, Infectious Diseases of Poverty)

   null (Ed.)

   Abstract Background Water resources development promotes agricultural expansion and food security. But are these benefits offset by increased infectious disease risk? Dam construction on the Senegal River in 1986 was followed by agricultural expansion and increased transmission of human schistosomes. Yet the mechanisms linking these two processes at the individual and household levels remain unclear. We investigated the association between household land use and schistosome infection in children. Methods We analyzed cross-sectional household survey data ( n  = 655) collected in 16 rural villages in August 2016  across demographic, socio-economic and land use dimensions, which were matched to Schistosoma haematobium ( n  = 1232) and S. mansoni ( n  = 1222) infection data collected from school-aged children. Mixed effects regression determined the relationship between irrigated area and schistosome infection presence and intensity. Results Controlling for socio-economic and demographic risk factors, irrigated area cultivated by a household was associated with an increase in the presence of S. haematobium infection (odds ratio [ OR ] = 1.14; 95% confidence interval [95% CI ]: 1.03–1.28) but not S. mansoni infection ( OR  = 1.02; 95% CI : 0.93–1.11). Associations between infection intensity and irrigated area were positive but imprecise ( S. haematobium: rate ratio [ RR ] = 1.05; 95% CI : 0.98–1.13, S. mansoni : RR  = 1.09; 95% CI : 0.89–1.32). Conclusions Household engagement in irrigated agriculture increases individual risk of S. haematobium but not S. mansoni infection. Increased contact with irrigated landscapes likely drives exposure, with greater impacts on households relying on agricultural livelihoods. 

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2. Schistosome infection in Senegal is associated with different spatial extents of risk and ecological drivers for Schistosoma haematobium and S. mansoni

   https://doi.org/10.1371/journal.pntd.0009712  

   Jones, Isabel J.; Sokolow, Susanne H.; Chamberlin, Andrew J.; Lund, Andrea J.; Jouanard, Nicolas; Bandagny, Lydie; Ndione, Raphaël; Senghor, Simon; Schacht, Anne-Marie; Riveau, Gilles; et al (September 2021, PLOS Neglected Tropical Diseases)

   Secor, W. Evan (Ed.)

   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. 

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3. Schistosome infection in Senegal is associated with different spatial extents of risk and ecological drivers for S. haematobium and S. mansoni.

   https://doi.org/https://doi.org/10.1371/journal.pntd.0009712  

   Jones IJ, Sokolow SH (September 2021, PLoS neglected tropical diseases)

   Schistosome parasites infect more than 200 million people annually, mostly in sub-Saharan Africa, where people may be coinfected 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. 

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4. Re-assessing thermal response of schistosomiasis transmission risk: Evidence for a higher thermal optimum than previously predicted

   Aslan, IH; Pourtois, JD; Chamberlin, AJ; Mitchell, KR; Mari, L; Lwiza, KM; Wood, CL; Mordecai, EA; Yu, A; Tuan, R; et al (June 2024, PLOS NEGLECTED TROPICAL DISEASES)

   None (Ed.)

   The geographical range of schistosomiasis is affected by the ecology of schistosome parasites and their obligate host snails, including their response to temperature. Previous models predicted schistosomiasis’ thermal optimum at 21.7°C, which is not compatible with the temperature in sub-Saharan Africa (SSA) regions where schistosomiasis is hyperendemic. We performed an extensive literature search for empirical data on the effect of temperature on physiological and epidemiological parameters regulating the free-living stages of S. mansoni and S. haematobium and their obligate host snails, i.e., Biomphalaria spp. and Bulinus spp., respectively. We derived nonlinear thermal responses fitted on these data to parameterize a mechanistic, process-based model of schistosomiasis. We then re-cast the basic reproduction number and the prevalence of schistosome infection as functions of temperature. We found that the thermal optima for transmission of S. mansoni and S. haematobium range between 23.1–27.3°C and 23.6–27.9°C (95% CI) respectively. We also found that the thermal optimum shifts toward higher temperatures as the human water contact rate increases with temperature. Our findings align with an extensive dataset of schistosomiasis prevalence in SSA. The refined nonlinear thermal-response model developed here suggests a more suitable current climate and a greater risk of increased transmission with future warming for more than half of the schistosomiasis suitable regions with mean annual temperature below the thermal optimum. 

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5. Rice–fish co-culturing reduces schistosomiasis risk and increases yields and incomes

   https://doi.org/10.1038/s41893-026-01833-8  

   Selland, Emily K; Jouanard, Nicolas; Guisse, Amadou; Seck, Momy; Lund, Andrea J; López-Carr, David; Sack, Alexandra; Magblenou, Louis Dossou; De_Leo, Giulio A; Doruska, Molly J; et al (July 2026, Nature Sustainability)

   NA (Ed.)

   Over 140 million households cultivate rice worldwide. However, rice production contributes to exceedance of planetary boundaries, such as freshwater use and biogeochemical flows. In addition, rice-farming families may face increased risk of contracting schistosomiasis, a parasitic disease transmitted by freshwater snails that contributes to reinforcing cycles of poverty and disease. Here, using data from 405 households in rural northern Senegal, we show that children in rice-farming households had higher Schistosoma mansoni prevalence and Schistosoma haematobium intensities than non-farming peers. To address this environmental health challenge, we integrated native Nile tilapia (Oreochromis niloticus) and African bonytongue (Heterotis niloticus) into rice fields. The fish thrived, suppressed insects and snail pests, improved soil nutrients and boosted rice yields by >25% with a net benefit of US$1,805–3,415 ha−1 yr−1 (a benefit-to-cost ratio of 7.42). Hence, low-input rice–fish co-culturing offers a sustainable planetary health solution that simultaneously improves agricultural outcomes and rural livelihoods while reducing disease transmission risks. 

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