Authors

Discussion

The life-cycle of Schistosoma haematobium, a trematode parasite, involves both humans and Bulinus freshwater snail species. Recent reports have identified Bulinus spp. novel to Lake Malawi, but their role in Schistosoma epidemiology is unknown. Due to the emergence of hybrids of S. haematobium and Schistosoma bovis south of Lake Malawi, this study sought to investigate the intermediate hosts of these Schistosoma spp., to identify parasite transmission foci, and determine potential areas for their hybridization. Infection screening was conducted on 106 snails collected in 2017 from the shoreline of Lake Malawi, Magochi Disrict, using both conventional and quantitative PCR xenomonitoring methods. Snails were selected for species identification (n=10) by inspecting a 644bp fragment of the cox1, which was later aligned to entries on GenBank. The distribution of Bulinus spp. and Schistosoma spp. was then mapped onto Mangochi district. Four snails were matched to sequences of Bulinus africanus and another identified as a Bulinus angolensis-like specimen. Although no snails were infected with S. bovis, the qPCR cycle threshold values indicated that individuals from both snail species were developing pre-patent infections with S. haematobium across the shoreline, including some Mangochi tourist beaches. This study builds on recent surveys implicating the newly reported B. africanus and B. angolensis-like snails in the transmission of S. haematobium in Lake Malawi for the first time. There is a risk for introduction of S. bovis and subsequent hybridisation with the endemic S. haematobium, as B. africanus is a competent host of both parasites. The finding of snails infected with S. haematobium on tourist beaches poses a risk for its translocation to non-endemic areas. Xenomonitoring will continue in Malawi, utilising novel Schistosoma species-specific TaqMan probes to ascertain the species identities of pre-patent infections in snails.