Distribution of freshwater gastropods in the lower River Niger and Cross River basins of southeastern Nigeria with reference to their trematode infections.

Malacological surveys on the abundance of molluscan fauna were carried out in freshwater habitats at the 2 main rivers of southeastern Nigeria: River Niger and Cross River basins. A total of 19 species of gastropods were found, 13 of which are pulmonates and 6 prosobranchs. The distribution of the species varied between the habitats, with high densities recorded in patches within the habitats. Infected snails were collected mainly from portions of the habitats that are accessible. Trematode cercariae types and infection rates were recorded for each snail species. Seasonal patterns of both snail types and their trematode infection at various developmental stages are discussed.