ARCUS | Arctic Research Consortium of the United States

7th Annual ARCUS Award for Arctic Research Excellence

Winner Life Science
Submitted by   Emily Jenkins
Authors   Emily Jenkins, A. M. Veitch, G. D. Appleyard, E. P. Hoberg, S. J. Kutz, and L. Polley
Category   Life Science
Title   Geographic Distribution and Seasonal Patterns of Larval Shedding of the Muscle-Dwelling Nematode Parelaphostrongylus odocoilei in Thinhorn Sheep from Northern North America
Affiliation   Department of Veterinary Microbiology, University of Saskatchewan, Saskatoon, SK, Canada

Abstract

In 2000, the muscleworm Parelaphostrongylus odocoilei (previously reported only in cervids and mountain goats) was identified in Dall's sheep (Ovis dalli dalli) from the Mackenzie Mountains, Northwest Territories (NT), Canada. Subsequently, we determined the geographic distribution of P. odocoilei through examination of fecal samples from thinhorn sheep (Ovis dalli), bighorn sheep (Ovis canadensis canadensis), and mountain goats (Oreamnus americanus) across northwestern North America. Larvae of P. odocoilei were recovered from several populations of thinhorn sheep and both populations of mountain goats examined, but were not present in the single bighorn sheep population examined. We confirmed the identity of these larvae by obtaining and comparing sequences of the ITS-2 region of ribosomal DNA to those of P. odocoilei validated using adult parasite identification. Our results demonstrated that P. odocoilei is established in the Mackenzie Mts. (NT), the Selwyn Mts. (Yukon Territory - YT), the central Alaska range (Alaska), the St. Elias Mts. (YT), the northern end of the Rocky Mts. (British Columbia), and the Coastal Mts. of BC. Sequence data were consistent for larvae in thinhorn sheep and mountain goats across this geographic range, suggesting that P. odocoilei is not differentiated into sub-species or ‘cryptic’ species. Our work represents the first application of molecular methods for identification of unknown protostrongylid larvae in a broad-based survey of geographic and host distribution. We also described seasonal variations in prevalence and intensity of larval shedding of P. odocoilei and the sheep lungworm Protostrongylus stilesi by examining fecal samples from a population of Dall's sheep in the Mackenzie Mountains bimonthly from March 2000 to March 2002. The prevalence of P. odocoilei larvae ranged from 87-100%, while the prevalence of P. stilesi larvae ranged from 75-100% except in August of each year, when the prevalence dropped to 18% (2000) and 32% (2001). The mean intensity of larval shedding for both P. odocoilei and P. stilesi displayed a consistent pattern in both years, peaking during late winter/early spring and reaching a trough in late summer. This combination of traditional parasitology and a novel application of molecular diagnostic techniques greatly expands knowledge of the geographic range and epidemiology of P. odocoilei in thinhorn sheep in Arctic and Sub-Arctic North America.