Meningeal Worm (parelaphostrongylus Tenuis) in South Dakota: the Parasite in Terrestrial Gastropods

Terrestrial gastropods were collected from wetland, grassland, and forested habitats throughout eastern and southcentral South Dakota from May-August of 1999 and 2000 to assess the role of gastropods in transmission of meningeal worm (Parelaphostrongylus tenuis) to white-tailed deer (Odocoileus virginianus) populations throughout the state. A total of 4,063 gastropods representing 14 species, five of which were known intermediate hosts for P. tenuis, were collected throughout South Dakota during the summers of 1999 and 2000. Significantly more (P < 0.0001) gastropods were collected from eastern than western South Dakota. Six species of snails (Zonitoides nitidus, Z. arboreus, Discus cronkhitei, Succinea ovalis, Gastrocopta pentadon, and Vallonia sp.) and one slug species (Deroceras laeve) accounted for 87% of the gastropods collected. A total of 3,468 gastropods were examined for presence of P. tenuis larvae. Three species of snails (Z. arboreus, Z. nitidus, and D. cronkhitei) and one slug species (Deroceras laeve) accounted for 93% of the total number of infected gastropods (i.e., 66 of 71). Significantly more (P = 0.005) infected gastropods were collected from semipermanent wetlands than from grasslands or forested habitats, suggesting that wetland habitats are important transmission sites of P. tenuis from gastropods to white-tailed deer in South Dakota.