The possible importance of wintering yards in the transmission of Parelaphostrongylus tenuis to white-tailed deer and moose

Terrestrial gastropods were collected, 15 June to 25 November 1994, from beneath cardboard sheets on deer range in northeastern Minnesota (USA) and examined individually for larvae of Parelaphostrongylus tenuis, the meningeal worm of white-tailed deer (Odocoileus virginianus). Overall, 10 (0.08%) of 12,096 snails and slugs were infected with a mean (+/-SD) of 3.2 +/- 2.5 P. tenuis larvae. The prevalence of infection in gastropods was greater in a traditional deer wintering yard (seven of 4,401, 0.16%), where deer aggregated for almost 5 months at a density of 50/km(2), than on summer range (three of 7,695, 0.04%) where they occurred at 4/km(2). Despite relatively low densities of infected gastropods, their ingestion purely by chance remains a tenable explanation for the high prevalence of P. tenuis infection observed in white-tailed deer.