ECOLOGY OF MENINGEAL WORM, PARELAPHOSTRONGLYUS TENIUS (NEMATODA) IN WHITE-TAILED DEER AND TERRESTRIAL GASTROPODS OF MICHIGAN'S UPPER PENINSULA WITH IMPLICAITONS FOR MOOSE

Abstract

Moose (Alces alces) were reintroduced to Michigan's Upper Peninsula in the mid-1980's. Because of some of the subsequent mortalities were attributed to meningeal worm, Parelaphostrongylus tenuis, a study was done in 1995 - 1996 to determine potential exposure of moose to this parasite. Objectives were to determine parasite population size in white-tailed deer (Odocoileus virginianus) of the region as well as the abundance and distribution of gastropod intermediate hosts with emphasis on their role in the transmission of P. tenuis. Prevalence and intensity of adult worms were lower in fawns (28%, all with 1 worm) than in older deer (51%, x̄ = 1.7). Numbers of first-stage larvae were more numerous in deer feces collected in winter and spring than in feces collected in summer and autumn. Gastropods, collected June - October 1995 and June - August 1996, were most abundant in lowland areas (predominantly mixed conifer - deciduous habitat). Canonical correspondence analysis showed that % canopy cover, soil type, and soil depth best explained the distribution of snails among 35 collection sites. Eight of 23 species of gastropods collected were infected with P. tenuis larvae; 2 members of the genus Discus spp. were considered to be the most important intermediate hosts. Deer concentrated in areas called 'yards' in winter. One such type of yard where deer were fed artificially tended to have more infected gastropods than other areas, but their role in transmission of P. tenuis to moose is probably limited for several reasons including that these sites were spatially separated from primary moose range. Another type of yard that involves logging activity poses some threat to moose because numbers of gastropods in it are relatively high and, unlike artificial feeding sites, it is more accessible to moose because of seasonal decreases in human activity.