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Title: Muellerius capillaris dominates the lungworm community of Bighorn Sheep at the National Bison Range, Montana

Author
item EZENWA, VANESSA - University Of Montana
item HINES, ALICIA - University Of Montana
item ARCHIE, ELIZABETH - University Of Montana
item Hoberg, Eric
item ASMUNDSSON, INGRID - US Department Of Agriculture (USDA)
item HOGG, JOHN - Montana Conservation Science Institute

Submitted to: Journal of Wildlife Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/25/2010
Publication Date: 7/1/2010
Citation: Ezenwa, V.O., Hines, A.M., Archie, E.A., Hoberg, E.P., Asmundsson, I.M., Hogg, J.T. 2010. Muellerius capillaris dominates the lungworm community of Bighorn Sheep at the National Bison Range, Montana. Journal of Wildlife Diseases. 46:988-993.

Interpretive Summary: Lungworm related pneumonia in wild sheep continues to be a considerable concern for populations of free-ranging hosts in western North America. However, we continue to have an incomplete knowledge about the distributions and sources for potentially pathogenic parasites, and how these may be exchanged among free-ranging and domestic ungulates. The structure of parasites faunas of ungulates in North America, including the species involved and their host and geographic distributions, continues to be documented by the process of survey and inventory involving field collections and reference to museum-based archives such as the US National Parasite Collection. New discoveries continue to accumulate as we reveal novel information about the distribution of many groups of parasites. One particular concern is the process of invasion by parasites, and how complex faunas undergo changes in host distribution. We have explored this process through studies of lungworm parasites which infect domestic and free-ranging ungulates in western North America. Lungworm infections are common among bighorn sheep (Ovis canadensis) in North America, and the predominant species reported are Protostrongylus stilesi and P. rushi. Currently, the only records of another lungworm species, Muellerius capillaris, infecting bighorns come from South Dakota. At the National Bison Range (NBR), Montana we found that 100% of wild bighorn sheep surveyed were passing first-stage dorsal-spined larvae (DSL) which appeared to be consistent with M. capillaris. Unequivocal identification of DSL based on morphology remains problematic due to potential confusion of M. capillaris with species of Parelaphostrongylus and Varestrongylus, a particular concern in areas where primary hosts including domestic stock or species of Odocoileus are in sympatry with wild sheep. Using molecular techniques, we positively identified DSL from the NBR bighorns as M. capillaris. This work provides a first definitive record of M. capillaris infection in a free-ranging bighorn sheep population outside of South Dakota. We suggest that the infections of this parasite in this population of bighorns were derived ultimately from contact with domestic stock, particularly sheep. It is currently unknown to what degree infections of M. capillaris in bighorns represent and emergent disease threat, suggesting further research is warranted.

Technical Abstract: Lungworm infections are common among bighorn sheep (Ovis canadensis) in North America, and the predominant species reported are Protostrongylus stilesi and P. rushi. Currently, the only records of another lungworm species, Muellerius capillaris, infecting bighorns come from South Dakota. At the National Bison Range (NBR), Montana we found that 100% of wild bighorn sheep surveyed were passing first-stage dorsal-spined larvae (DSL) which appeared to be consistent with M. capillaris. Unequivocal identification of DSL based on morphology remains problematic due to potential confusion of M. capillaris with species of Parelaphostrongylus and Varestrongylus, a particular concern in areas where primary hosts including domestic stock or species of Odocoileus are in sympatry with wild sheep. Using molecular techniques, we positively identified DSL from the NBR bighorns as M. capillaris. This work provides a first definitive record of M. capillaris infection in a free-ranging bighorn sheep population outside of South Dakota.