DISTRIBUTION OF SNAIL INTERMEDIATE HOST OF SCHISTOSOMIASIS IN RIVER NIGER WATERS, LOKOJA

Abstract

This study aimed to investigate the distribution, abundance, and infection status of these snail intermediate hosts in Lokoja, Kogi State, Nigeria. Lokoja is of particular interest due to its unique location at the confluence of the Niger and Benue rivers, which creates ideal habitats for these snail vectors. A six-month longitudinal survey (May to Oct. 2022) was conducted across three identified hotspots in Lokoja: Kpata, Adankolo, and Ganaja settlements. A total of 1500 snail specimens were sampled using an improvised scoop net, identified based on Danish Bilharzia Laboratory, and examined for cercariae emergence using artificial illumination (60 watts bulb) for 4 to 6 hours. The results revealed the consistent presence of Bulinus globosus (36%) and Biomphalaria pfeifferi (30%) across all study locations, Snails belonging to the genera Bulinus and Biomphalaria were identified across the various study sites. These snails were confirmed to be active intermediate hosts for Schistosoma haematobium and Schistosoma mansoni, respectively. This identification was established following the emergence and identification of patent schistosome cercariae during shedding assays. Significant spatial heterogeneity was observed, with Ganaja presenting a distinct ecological profile characterized by a higher prevalence of Melanoides tuberculata (37%). The result revealed significant differences (p<0.05). Snail abundance also demonstrated clear seasonal variations: Biomphalaria pfeifferi was most abundant during the dry season (35.0%), while Bulinus globosus dominated in the rainy season (41.0%). Overall, snail populations peaked in June–July before sharply declining toward October. Importantly, cercariae emergence was confirmed; Bulinus globosus showed the highest infestation rate (9.91%), followed by Biomphalaria pfeifferi (5.17%), with Melanoides tuberculata exhibiting no infestation. These findings are critical for understanding the epidemiology and transmission 
dynamics of schistosomiasis in this endemic area, providing essential baseline data for developing targeted and effective control strategies.