Changing patterns of Schistosoma host snail population densities in Maun, Botswana

Abstract

Changes in the inflow of water into the Thamalakane River had been predicted to alter snail population dynamics and influence the risk of schistosomiasis transmission in Maun. We determined the abundance of schistosome intermediate host snails along the Thamalakane River and evaluated the risk of schistosomiasis infection within Maun. A retrospective study utilised snail survey data previously collected from the Thamalakane River in Maun between June 2009 and July 2012. A total of 3 563 freshwater snails were collected from 10 sentinel sites along Thamalakane River. The snails collected were Bulinus globosus, Biomphalaria pfeifferi, Lymnaea natalensis, Bellamya capillata, Pila occidentalis and Lanistes ovum. Bulinus globosus snails were more abundant than B. pfeifferi. None of the intermediate host snails (IHS) collected shed cercariae. The absence of infected IHS suggests that there was no active transmission of schistosomiasis during the study period. Furthermore, the presence of B. globosus in the Thamalakane River suggests the potential risks of Schistosoma haematobium infection when transmission conditions become conducive.