Hydrological modelling of snail dispersal patterns in Msambweni, Kenya and potential resurgence ofSchistosoma haematobiumtransmission

Abstract

SUMMARYUrinary schistosomiasis is an important source of human morbidity in Msambweni, Kenya, where the intermediate host snail,Bulinus nasutusis found in ponds and water pools. In the past, aquatic habitats in the area have been studied separately; however, recent collections ofB. nasutussnails and shells indicated that many of these ponds are in fact connected during and following sufficient rains. Satellite imagery and a geographical information system (GIS) were used to survey the main water courses and potential drainage routes, to locate potential source populations of snails and to determine probable snail dispersal routes. The 2 water bodies implicated as being the most importantSchistosoma haematobiumtransmission foci in the area were found to differ in their degree of connectivity to otherB. nasutussource habitats. One pond becomes connected even after normal rains, while the other pond requires prolonged rains or flooding to become connected with source habitats. Consequently, the transmission foci differ in their susceptibility to snail population control measures. Spatially explicit dispersal models that consider the spatial and temporal patterns of connectivity between aquatic habitats will contribute to improved snail surveillance and more focused control for urinary schistosomiasis at a local level.