Infectivity Status and Transmission Potential of Freshwater Snails at Lake Njoboliyo, Adamawa State, Nigeria

Abstract

A study was conducted to assess the infectivity and transmission potential of freshwater snail intermediate hosts at Lake Njoboliyo,  Adamawa State, Nigeria. Snail samples were collected monthly from November 2023 to March 2024 using a scoop net with a 2 cm mesh  size, supplemented by handpicking. In total, 1,602 freshwater snails were collected and identified to species level based on their morphological characteristics using standard identification keys. The snail species observed were: Melanoides tuberculata (490, 30.6%),  Bellamya unicolor (387, 24.2%), Pila ovata (328, 20.5%), Lanistes ovum (288, 17.9%), Lymnaea natalensis (74, 4.6%), Bulinus globosus (19,  1.2%), Cleopatra bulimoides(10, 0.6%), and Bulinus truncatus(6, 0.4%). The snails were screened for natural infections by exposing them  individually to sunlight for two hours in pre-labeled shedding vials containing 10 mL of filtered water from their collection site. The results  showed that Lanistes ovum and Pila ovata were the only snail species naturally infected, though, of non-human schistosomes. No  cercariae were shed by Bulinus globosus, B. truncatus, Lymnaea natalensis, or other species. There was no significant difference in  infection rates between the infected snails (p > 0.05). The overall infection rate at Lake Njoboliyo was 2.75%, with Lanistes ovum and Pila  ovata showing infection rates of 10.70% and 3.96%, respectively. The highest infection rate was observed in December, at 3.87%,  coinciding with the highest transmission potential of 32.91%. No significant difference in infection rates was found across the sampling  months (p > 0.05). However, Bulinus species showed 0.00% infection and transmission potential, as did other snail species. These findings highlight the importance of implementing targeted interventions during specific months to control snail-borne diseases at Lake Njoboliyo. An  effective snail control program and public awareness efforts about the role of snails in disease transmission are strongly recommended.