Populations of Biomphalaria spp. Snails Isolates in Kenya Show Variable Resistance to Schistosome Infection

Abstract

Fresh water snails of genus Biomphlaria, Bulinus and Ocomelinia are important vectors for human schistosomiasis. Human contact patterns with water infested with cercaria are important factors in transmission of schistosomiasis and these conditions are associated with tropical climate wetlands. However, some snail strains within the genera that transmit cercaria are resistant to infection, providing means where these traits can be harnessed for biological control. PCR rDNA probes were used to determine miracidia/cercaria infected Biomphalaria snail isolates within Kenya. The derived sequences together with similar Genbank datasets were applied in phylogenetic analysis. PCR results showed that susceptibility/resistance trait occurs in proportion of the field sampled snails and also those maintained in laboratory culture. Phylogenetic analysis of sampled snails in this study together with composite dataset of similar rDNA sequences across Africa showed that Biomphalaria spp population structure is composed of distinct monophyla lineages and clusters of closely related isolates or clones. Further, the analysis indicated that nomenclature of Biomphalaria spp. classification needs revision. This provides evidence for resistance to cercaria transmission in some isolates of Biomphalaria spp. within Kenya but the trait does not cluster together in phylogenetics that is based on rDNA gene.