Modelling the future distribution of Schistosoma-transmitting snails in South Africa using climate projections

Schistosomiasis is a disease caused by trematode worms and transmitted through specific gastropod snails, namely Bulinus africanus, Bulinus globosus, and Biomphalaria pfeifferi. The distribution of Schistosoma species is influenced by climate factors such as temperature and rainfall. Understanding the impact of climate change on these factors is crucial for predicting changes in schistosomiasis transmission. This study employed bioclimatic variables to forecast the future distribution of these snail species in South Africa, utilising three ecological models alongside three General Circulation Models (GCMs) under two emission scenarios (RCP4.5 and RCP8.5) for the periods 2040–2070 and 2070–2100. The predicted impacts of climate change on Schistosoma-transmitting snails in South Africa indicate a shift in habitat suitability for these intermediate hosts. Bulinus africanus may see a reduction in habitats across several provinces, but could expand into the southwest coast and central Free State. Biomphalaria pfeifferi is expected to encounter decreased suitability in the eastern regions of South Africa but may find new habitats in the Free State, Northern Cape, and western areas. Bulinus globosus is likely to face habitat declines but could adapt to suitable climates in the Free State and KwaZulu-Natal regions. These shifts suggest that warming climates may create new habitats for these snail species at higher elevations and cooler areas. This study established a foundational framework for subsequent research at the provincial and municipal levels. This can be a foundation for developing strategies to prevent transmission and range expansion of schistosomiasis into previously unaffected areas.