An examination of the manipulation hypothesis to explain prevalence of <i>Parelaphostrongylus tenuis</i> in gastropod intermediate host populations

Abstract

There are many examples of parasites that manipulate intermediate host behaviour facilitating transmission to the definitive host. We examined this hypothesis as a possible explanation for the observed prevalence of Parelaphostrongylus tenuis, a nematode parasite of white-tailed deer (Odocoileus virginianus) in eastern North America. The prevalence of this parasite in deer populations is typically high compared with its prevalence in its gastropod intermediate hosts. It is unclear how high levels of prevalence are maintained, given that the transmission of this parasite to deer is considered to occur by the accidental ingestion of infected gastropods. We tested the manipulation hypothesis by comparing the vertical climbing behaviour of infected and uninfected individuals of a known intermediate host species, Mesodon sayanus. Snails climbed higher at dawn than during the rest of the day and adults climbed higher than juveniles, but no differences were found between infected and uninfected snails. These res...