Delineation of potential urban urogenital schistosomiasis transmission areas in Osogbo, south-west Nigeria

Schistosomiasis is ranked second to malaria among parasitic diseases of socio-economic and public health importance. One of the crucial factors in monitoring the current and future status and distribution of S. haematobium infection in Nigeria is to improve the knowledge on the freshwater snails that play an indispensable role in its transmission. The present study was undertaken to delineate potential transmission areas of urogenital schistosomiasis in Osogbo Metropolis using snail intermediate hosts and human-water contact as indicators. The major rivers/streams were visited bimonthly at various locations between April and July, 2016 and snail samples were collected using scoopers. The snails were identified morphologically and exposed to artificial light for cercaria shedding. Human water contact activities were observed at the sites where snails were recovered and relative index of exposure was calculated for each activity. Of the nine locations visited, only four were positive, namely; Gbodofon (Osun River), Isale Osun (Osun River), area 264 (Oniti Stream) and Gbonmi (Okoko Stream). Even though, none of the exposed snails shed cercaria, the human activities were observed at the sites. The results showed that 49.7% of the human contacts were for swimming followed by Fishing (32.2%), cloth-washing (10.1%) and spiritual/ritual bath (8.0%). Swimming has the highest relative index of exposure (RIE=30231) while spiritual/ritual bath has the least (RIE=96). The presence of the snail intermediate hosts at the four sites coupled with human water activities as observed in the present study suggest the risk of urogenital schistosomiasis at the study-area. Keywords: Bulinus species; schistosome; human water contact; Osogbo; Nigeria