Certain species of them can be found in almost any tissue of the body. Some of them migrate through the body in various stages of development. While in migration they pose different problems than they do when in the intestinal tract which can be more difficult to treat. The nematodes that infect mice and rats are the Oxyurids, commonly called Pinworms. Syphacia obvelata, Aspiculuris tetraptera, and Syphacia muris, are the species that infect them both, with the latter being the main pinworm of rats.
Pinworms are basically commensal, which means they neither harm nor benefit the host.
Even gerbils and hamsters may be infected with these. There is another nematode that is pathogenic in rats. This is Trichosomoides crassicauda, a threadworm found in the bladder. It produces few signs of disease, and none of these mentioned so far are considered a threat to humans. Mice, rats, gerbils, and hamsters are the definitive hosts for the tapeworms called Hymenolepis nana, Hymnenolepis diminuta.