Oncomelania

Oncomelania is a genus of very small tropical freshwater snails, aquatic gastropod mollusks in the family Pomatiopsidae.

Various Oncomelania species are significant medically, because they can serve as vectors for two serious human diseases: they can carry the schistosomiasis blood fluke parasite, and the paragonimus lung fluke parasites.

These Oncomelania snails are distantly related to the marine periwinkle, and more closely related to the small marine snails of the family Rissoidae.