Complex life cycle of Pterygodermatites peromysci, a trophically transmitted parasite of the white-footed mouse (Peromyscus leucopus)

The aim of this study is to experimentally verify the intermediate host of a common gastrointestinal nematode, Pterygodermatites peromysci, infecting the white-footed mouse (Peromyscus leucopus) and describe the complex life cycle. As with other nematodes in the family Rictulariidae, adult worms reside in the small intestine of the host, and infective eggs are shed into the environment where they are ingested by scavenger insects. A field survey of common nocturnal insects on the forest floors of central Pennsylvania was conducted to identify the putative intermediate host. Encysted nematode larvae were recovered from the hemocoel of three species of camel cricket, Ceuthophilus pallidipes, Ceuthophilus guttulosus, and Ceuthophilus gracilipes. The mean prevalence of infection was 11-17%, and the intensity of infection ranged from 1 to 41 cysts per cricket. Laboratory white-footed mice were infected with cysts harvested from the three species of crickets. Cysts taken from the C. pallidipes produced the highest level of infection (41%); the adult worms recovered from the mice were confirmed as P. peromysci. Laboratory infections of naive C. pallidipes with P. peromysci eggs yielded a 70% infection rate, further verifying that the cricket C. pallidipes is a suitable intermediate host for P. peromysci. We discuss the importance of identifying the intermediate host for understanding the transmission dynamics of a trophically transmitted parasite.