Metastrongylid nematodes are characterized by having life cycles that typically require an intermediated molluscan host for the development of the third-stage larvae that are infective to vertebrates. Cats do not appear to eat many snails, and typically acquire their infections with these worms through the ingestion of paratenic hosts, e.g., small birds or rodents. The majority of metastrongyles are associated with lung tissue, although the adults are often living within associated blood vessels. There are four metastrongyles that have been reported from the domestic cat. One species, Aelurostrongylusabstrusus, is rather common. The other three species, Troglostrongylussubcrenatus, Oslerus rostratus, and Gurltiaparalysans have only rarely been reported from cats and probably represent species typically parasitic in wild felids or some other non-domestic mammal.