Prevalence of parasites in freshwater snails with notes on helminth-associated diseases in Balo-i Lake, Lanao del Norte, Philippines

Abstract Freshwater snails play crucial roles in aquatic habitats with essential ecosystem functions and services. However, they also serve as intermediate hosts for various parasites that pose risks to human and animal health. This study aimed to identify freshwater snail species with parasite infection and assess parasite prevalence in Balo-i Lake, Lanao del Norte, Philippines. Snail samples were collected from three sites (Power Plant area, Residential area, and Agricultural area) around the lake utilizing the belt transect method, and parasites were identified based on morphological characteristics. Physicochemical parameters were measured to explore their correlation with parasite prevalence. Results revealed a total prevalence rate of 3.78% (95% CI 2.372–5.966) among five freshwater snail species – S. angularis (n = 26), P. acuta (n = 22), M. maculata (n = 81), M. tuberculata (n = 44), and R. quadrasi (n = 5), with notable variations among sampling sites and seasonal variation between wet and dry seasons. M. maculata harbored the most parasites, with three cercarial morphotypes and a nematode. Trematodes were the most abundant parasites, with five morphotypes identified, namely Cercarium cercariae, Gymnocephalous cercariae, Parapleurolophocercous cercaria, Echinostome cercariae, and Strigea cercariae, most of which are produced by intestinal parasites of fish, birds, and mammals. Gymnocephalous cercariae infected most snail individuals (n = 6), but Parapleurolophocercous cercaria was the most common, infecting three snail species across two sampling sites. The residential area has the highest prevalence rate of infection, likely influenced by frequent human activities like bathing, washing clothes, pollution, and the presence of potential hosts such as ducks, amphibians, and mammals in adjacent areas. Weak correlations between parasite prevalence and pH and temperature suggest additional influencing factors. The presence of parasites highlights public health concerns, emphasizing the need for control measures and ecosystem conservation to mitigate disease transmission in the area.