Parasites of Ovis canadensis canadensis in Montana, with a Checklist of the Internal and External Parasites of the Rocky Mountain Bighorn Sheep in North America

Abstract

Eighteen Rocky Mountain bighorn sheep in Montana were examined for parasites at necropsy. Twelve came from the National Bison Range, five from Wildhorse Island (Flathead Lake), and one from the Sun River area. The parasites recovered were: Cysticercus tenuicollis, Wyominia tetoni, Marshallagia marshali, Ostertagia circumcincta, O. lyrata, O. occidentalis, O. ostertagi, Cooperla oncophora, C. sumabada, Nematodirus archari, N. davtiani, N. helvetlanus, N. lanceolatus, N. spathiger, Trichostrongylus sp. (unidentified females), Protostrongylus rushi, Dermacentor albipictus, and D. venustus. Gastrointestinal nematodes recovered from the National Bison Range sheep ranged in number from 275 to 5300 per host and those from the Wildhorse Island sheep from 670 to 3510. The species recovered from the National Bison Range sheep were totally different from those recovered from the Wildhorse Island and Sun River sheep. The parasites recovered represent several new host and distribution records. Included in this report is a checklist of 51 species from Ovis canadensis, based on the present report, unpublished records of specimens in the U.S. National Museum Helminthological Collection, and from the literature. Seventy% of these 51 species are known parasites of domestic sheep and 35% of cattle in North America.