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United States Department of Agriculture

Agricultural Research Service

Title: Protostrongylid parasites and pneumonia in captive and wild thinhorn sheep (Ovis dalli).

Authors
item Jenkins, E - CANADA
item Veitch, A - CANADA
item Kutz, S - CANADA
item Bollinger, T - CANADA
item Chirino-Trejo, M - CANADA
item Elkin, B - CANADA
item West, K - CANADA
item Hoberg, Eric
item Polley, L - CANADA

Submitted to: Journal of Wildlife Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 10, 2006
Publication Date: March 4, 2007
Citation: Jenkins,E.J., Veitch,A.M., Kutz,S.J., Bollinger,T., Chirino-Trejo,M., Elkin, B.T., West,K., Hoberg,E.P., Polley,L. 2007. Protostrongylid parasites and pneumonia in captive and wild thinhorn sheep (Ovis dalli). Journal of Wildlife Diseases. 43:189-205.

Interpretive Summary: Parasites are significant factors in health and mortality of both wild and domestic ungulates, but we continue in many cases to lack clear data and conclusions about the mechanisms of disease. Increasingly interactions between wild and domestic hosts ate the interfaces (ecotones) of natural and managed ecosystems act as determinants of distribution for parasites and pathogens. In order to predict the outcomes of such interactions and to take a proactive approach for management of both wild ungulates and domestic stock we require accurate information about parasite biology and behavior. We describe the role of protostrongylid parasites (Parelaphostrongylus odocoilei and Protostrongylus stilesi) and other respiratory pathogens in the health of thinhorn sheep (Ovis dalli). Our conclusions are based on studies of parasite localization and associated pathology in over 50 naturally-infected Dall’s sheep (O. d. dalli) from the Mackenzie Mountains, Northwest Territories, as well as in three Stone’s sheep (Ovis dalli stonei) experimentally infected with P. odocoilei. Histological lesions in the brain and distribution of P. odocoilei in the muscles of experimentally and naturally infected sheep were consistent with a previously hypothesized ‘central nervous system to muscle’ migration pattern for P. odocoilei. In the lungs, size of granulomas associated with eggs of P. odocoilei and density of protostrongylid eggs and larvae in the cranial lung were significantly correlated with intensity of larvae of P. odocoilei in feces, and varied with season of collection. Due to marked seasonal effects on larval production and focal distribution of lesions in the lungs, prevalence of P. stilesi based on examination of lungs did not correlate with that based on presence of larvae of P. stilesi in feces. Diffuse, interstitial pneumonia due to P. odocoilei led to fatal pulmonary hemorrhage and edema following exertion in one experimentally infected Stone’s sheep and one naturally infected Dall’s sheep. Protostrongylid parasites, especially P. odocoilei, may be predisposing factors in the development of acute or chronic bacterial pneumonia (associated with Arcanobacterium pyogenes, Pasteurella sp., and Mannheimia sp.), which caused sporadic mortalities in this population of Dall’s sheep. There was no evidence of respiratory viruses or bacterial strains characteristically associated with domestic animals, nor of an epizootic pattern of mortality due to respiratory disease in Dall’s sheep of the Mackenzie Mountains. Domestic livestock harbor parasites, viruses, and strains of bacteria to which thinhorn sheep are naïve, but likely susceptible. Thinhorn sheep are also likely susceptible to the same ecological factors (such as habitat fragmentation and degradation) that have hampered conservation efforts for bighorn sheep. Therefore, efforts to avoid translocation, contact with domestic animals, and anthropogenic stressors are a sound basis for proactive management for thinhorn sheep in North America, and may forestall the breakdown of protective ecological barriers that are maintained by isolation and distance.

Technical Abstract: We describe the role of protostrongylid parasites (Parelaphostrongylus odocoilei and Protostrongylus stilesi) and other respiratory pathogens in the health of thinhorn sheep (Ovis dalli). Conclusions are based on studies of parasite localization and associated pathology in over 50 naturally-infected Dall’s sheep (O. d. dalli) from the Mackenzie Mountains, Northwest Territories, as well as in three Stone’s sheep (Ovis dalli stonei) experimentally infected with P. odocoilei. Histological lesions in the brain and distribution of P. odocoilei in the muscles of experimentally and naturally infected sheep were consistent with a previously hypothesized ‘central nervous system to muscle’ migration pattern for P. odocoilei. In the lungs, size of granulomas associated with eggs of P. odocoilei and density of protostrongylid eggs and larvae in the cranial lung were significantly correlated with intensity of larvae of P. odocoilei in feces, and varied with season of collection. Due to marked seasonal effects on larval production and focal distribution of lesions in the lungs, prevalence of P. stilesi based on examination of lungs did not correlate with that based on presence of larvae of P. stilesi in feces. Diffuse, interstitial pneumonia due to P. odocoilei led to fatal pulmonary hemorrhage and edema following exertion in one experimentally infected Stone’s sheep and one naturally infected Dall’s sheep. Protostrongylid parasites, especially P. odocoilei, may be predisposing factors in the development of acute or chronic bacterial pneumonia (associated with Arcanobacterium pyogenes, Pasteurella sp., and Mannheimia sp.), which caused sporadic mortalities in this population of Dall’s sheep. There was no evidence of respiratory viruses or bacterial strains characteristically associated with domestic animals, nor of an epizootic pattern of mortality due to respiratory disease in Dall’s sheep of the Mackenzie Mountains.

Last Modified: 7/23/2014