Lungworms in the Rocky Mountain bighorn sheep of western Canada

Abstract

In 58 sets of lungs from bighorns from western Alberta or eastern British Columbia, 91% were infected with Protostrongylus stilesi, and 38% were infected with P. rushi. Four of the five sheep free of P. stilesi were lambs. Lungs from nine near-term fetuses were negative for lungworms.All but 1 of 409 field-collected fecal samples from the same ranges contained larvae of Protostrongylus spp.; counts of larvae per gram of dry feces suggest a clumped distribution of lungworms. Analysis of monthly samples from one herd indicated a significant seasonal variation, with high numbers of larvae shed by bighorns on winter range. The use of fecal analyses in assessing severity of infection and the evolutionary significance of the clumped distribution of lungworms are discussed.