Trematode cercariae infections in freshwater snails of Chitwan district, central Nepal

Abstract

Because Nepal has been virtually unexplored with respect to its trematode fauna, we sampled freshwater snails from grazing swamps, lakes, rivers, swamp forests, and temporary ponds in the Chitwan district of central Nepal between July and October 2008. Altogether we screened 1,448 individuals of nine freshwater snail species (Bellamya bengalensis, Gabbia orcula, Gyraulus euphraticus, Indoplanorbis exustus, Lymnaea luteola, Melanoides tuberculata, Pila globosa, Thiara granifera and Thiara lineata) for shedding cercariae. A total of 4.3% (N=62) infected snails were found, distributed among the snail species as follows (B. bengalensis - 1, G. orcula - 11, G. euphraticus - 8, I. exustus - 39, L. luteola - 2 and T. granifera - 1). Collectively, six morphologically distinguishable types of trematode cercariae were found: amphistomes, brevifurcate-apharyngeate (likely mammalian schistosomes), clinostome, gymnocephalus (likely fasciolid), longifurcate-pharyngeate and xiphidiocercaria. I. exustus had the highest prevalence of trematode infection, and harbored all the noted cercarial types except gymnocephalus cercariae. One double infection (xiphidiocercaria and longifurcate-pharyngeate cercaria) was found in this snail. Amphistome cercariae were common in G. euphraticus, G. orcula, and I. exustus. The highest prevalence of infection (38.3%) was recorded among snails collected from temporary ponds. DOI: http://dx.doi.org/10.3126/hjs.v7i9.2183 Himalayan Journal of Sciences Vol.7 Issue 9 2011 pp.9-14