Research seminar by Martin Stendel: Nasty little snails, schistosomiasis and climate change – a case study from Zimbabwe
Freshwater snails are intermediate hosts for a number of parasites of medical and veterinary importance. These trematodes rely on specific species of snails to complete their life cycle; hence the ecology of the snails is a key element in transmission of the parasites. Almost 300 million people, 95% of them in sub-Saharan Africa, are infected with schistosome parasites, and another 600 million are in danger of infection. Schistosomiasis, also known as bilharzia or snail fever, is a nasty disease that can affect the urinary tract, intestines, liver, kidneys, lungs, veins and even the brain. It ranks second only behind malaria in terms of socio-economic and public health importance in tropical and subtropical areas, and an estimated 200000 people die from it every year.
A biology-driven model for the freshwater snails Bulinus globosus, Biomphalaria pfeifferi and Lymnaea natalensis was used to make projections of snail habitat suitability, including potential underlying environmental and climatic drivers. The snail observation data originated from a nationwide survey in Zimbabwe, and the projection model was parameterized with HIRHAM5 data. The projections of snail habitat suitability were calibrated with georeferenced prevalence data. Snail habitat suitability across Zimbabwe, as well as the spatial distribution of snails, was investigated for three time slices representative for present-day (1980-1999) and future climate (2046-2065 and 2080-2099).
Under present-day conditions, snail habitat suitability is highly variable in Zimbabwe, with distinct high- and low-suitability areas. Temperature appears to be the main driving factor. Under future climate conditions, the suitable habitat of host snails is reduced, as temperatures increase and precipitation decreases.
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