Molecular diversity of Bulinus species in Madziwa area, Shamva district in Zimbabwe: implications for urogenital schistosomiasis transmission

Abstract

AbstractBackgroundBulinusspecies are freshwater snails that transmit the parasitic trematodeSchistosoma haematobium. Despite their importance, the diversity of these intermediate host snails and their evolutionary history is still unclear in Zimbabwe.Bulinus globosusandB. truncatuscollected from a urogenital schistosomiasis endemic region in the Madziwa area of Zimbabwe were characterized using molecular methods.MethodsMalacological survey sites were mapped and snails were collected from water contact sites in four communities in the Madziwa area, Shamva district for a period of one year, at three-month intervals.Schistosoma haematobiuminfections in snails were determined by cercarial shedding and the partial mitochondrial cytochromecoxidase subunit 1 gene (cox1) was used to investigate the phylogeny and genetic variability of theBulinusspp. collected.ResultsAmong the 1570Bulinusspp. snails collected, 30 (1.9%)B. globosuswere shedding morphologically identified schistosomes. None of theB. truncatussnails were shedding. The mitochondrialcox1 data from 166 and 16 samples forB. globosusandB. truncatus, respectively, showed genetically diverse populations within the two species. Twelvecox1 haplotypes were found from the 166B. globosussamples and three from the 16B. truncatussamples with phylogenetic analysis showing that the haplotypes fall into well-supported clusters within their species groups. BothB. truncatusandB. globosusclustered into two distinct lineages. Overall, significant negative values for both Tajima’s D statistic and the Fu’s Fs statistic were observed forB. globosusandB. truncatus.ConclusionsThe study provided new insights into the levels of genetic diversity withinB. globosusand additional information onB. truncatuscollected from a small geographical area in Zimbabwe. Low prevalence levels of infection observed in the snails may reflect the low transmission level of urogenital schistosomiasis in the area. Our results contribute towards the understanding of the distribution and population genetic structure ofBulinusspp. supporting the mapping of the transmission or risk of transmission of urogenital schistosomiasis, particularly in Zimbabwe.