Malacological survey and geospatial distribution of Indoplanor bisexutus (Deshayes, 1934) and Lymnaea natalensis (Krauss 1848) snail vectors of trematode parasites, in Abeokuta, south-western, Nigeria

Abstract

Vector snails of trematode parasites are important because of their role in the transmission of parasitic diseases. However, information on the diversity and distribution of snail hosts in Abeokuta area of Ogun State is scanty. Snails were collected from 31 water bodies including streams, rivers and dams on a monthly basis for six months. The snails were identified using shell morphology and examined for cercariae shedding. Collection sites were geo-referenced. Environmental data, Normalized Difference Vegetation Index (NDVI), Land Surface Temperature (LST), rainfall and Land cover corresponding to these locations were derived from Moderate resolution Imaging Spectroradiometer (MODIS). Binary logistic regression analysis was used to create spatial maps and predictive model map for snail species distribution. A total of 87 vector snails were collected; Lymnaea natalensis 65 (74.71%) and Indoplanor bisexutus 22 (25.29%).Nine out of 22I. exutus collected shed microcercouscercariae. Infected I. exutus, intermediate snail host of Schistosoma nasale, a cattle schistosome was found in two sites. The logistic regression analysis using remotely-sensed environmental data showed that NDVI was the significant variable influencing I. exutus distribution (B = -8.460, Sig = 0.043). Geospatial distribution maps were created to show the distribution of each snail species and potential transmission sites. This study mapped the distribution of snail hosts, identified possible transmission sites and demonstrates the presence of snail hosts of certain parasites in Abeokuta area (Abeokuta South and Abeokuta North Local Government Areas), the distribution of these snail hosts should be monitored to prevent transmission of these pathogens to humans.

Keywords: geospatial, vector snails, trematode, distribution, malacological