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United States Department of Agriculture

Agricultural Research Service

Title: Geographic Distribution of the Muscle-Dwelling Nematode Parelaphostrongylus Odocoilei in North America, Using Molecular Identification of First-Stage Larvae

Authors
item Jenkins, Emily - CANADA
item Appleyard, Greg - CANADA
item Hoberg, Eric
item Rosenthal, Benjamin
item Kutz, Susan - CANADA
item Veitch, Alasdair - CANADA
item Schwantje, Helen - CANADA
item Elkin, Brett - CANADA
item Polley, Lydden - CANADA

Submitted to: Journal of Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 17, 2004
Publication Date: September 7, 2004
Citation: Jenkins, E.J., Appleyard, G.D., Hoberg, E.P., Rosenthal, B.M., Kutz, S.J., Veitch, A.M., Schwantje, H.M., Elkin, B.T., Polley, L. 2004. Geographic distribution of the muscle-dwelling nematode Parelaphostrongylus odocoilei in North America, using molecular identification of first-stage larvae. Journal of Parasitology. 91:574-584.

Interpretive Summary: Protostrongyle nematodes include pathogenic parasites that reside in the pulmonary system, skeletal musculature, or the central nervous system of their ruminant hosts. Identification based on either adult in tissue and tissue spaces, or larval parasites in feces has remained problematic, and has hampered a detailed understanding of host distribution and geographic range. Such information is critical in defining the potential for disease, and the degree to which parasites may be shared among a number of different ungulates. We applied a combination of comparative morphology and molecular analyses to define the host and geographic range for Parelaphostrongylus odocoilei in North America. Molecular identification of dorsal-spined larvae (DSL) indicates that the protostrongylid parasite Parelaphostrongylus odocoilei occupies a broader geographic range in western North America than previously reported. We analyzed 2,124 fecal samples at 29 locations from thinhorn sheep (Ovis dalli dalli and O. d. stonei), bighorn sheep (Ovis canadensis canadensis and O. c. californiana), mountain goats (Oreamnos americanus), woodland caribou (Rangifer tarandus caribou), mule deer (Odocoileus hemionus hemionus), and black-tailed deer (O. h. columbianus). DSL were recovered from populations of thinhorn sheep south, but not north, of the Arctic Circle, and were not recovered from any of the bighorn sheep populations examined. DSL were identified as P. odocoilei by comparing sequences of the second internal transcribed spacer (ITS2) region of ribosomal RNA among 9 protostrongylid species validated by adult comparative morphology. ITS2 sequences were markedly different among Parelaphostrongylus and other protostrongylid genera. The concepts demonstrated in our study are significant in the realm of molecular epidemiology and in circumstances where ruminant hosts cannot be collected for detailed necropsy. Our research represents the first study to combine extensive fecal surveys, comparative morphology, and molecular diagnostic techniques to comprehensively describe the host associations and geographic distribution of a parasitic helminth. The development of such epidemiological probes will have significant applications in veterinary and conservation medicine.

Technical Abstract: Molecular identification of dorsal-spined larvae (DSL) indicates that the protostrongylid parasite Parelaphostrongylus odocoilei occupies a broader geographic range in western North America than previously reported. We analyzed 2,124 fecal samples at 29 locations from thinhorn sheep (Ovis dalli dalli and O. d. stonei), bighorn sheep (Ovis canadensis canadensis and O. c. californiana), mountain goats (Oreamnos americanus), woodland caribou (Rangifer tarandus caribou), mule deer (Odocoileus hemionus hemionus), and black-tailed deer (O. h. columbianus). DSL were recovered from populations of thinhorn sheep south, but not north, of the Arctic Circle, and were not recovered from any of the bighorn sheep populations examined. In total, DSL were recovered from 20 locations in Alaska, Yukon Territory, Northwest Territories, British Columbia, Alberta, and California. DSL were identified as P. odocoilei by comparing sequences of the second internal transcribed spacer (ITS2) region of ribosomal RNA among 9 protostrongylid species validated by adult comparative morphology. ITS2 sequences were markedly different among Parelaphostrongylus and other protostrongylid genera. Fewer fixed differences served as diagnostic markers for the three species of Parelaphostrongylus. ITS2 sequences (n=60) of P. odocoilei were strongly conserved across its broad geographic range from California to Alaska. Polymorphism at 5 nucleotide positions was consistent with multiple copies of the ITS2 within individual specimens of P. odocoilei. Our research represents the first study to combine extensive fecal surveys, comparative morphology, and molecular diagnostic techniques to comprehensively describe the host associations and geographic distribution of a parasitic helminth.

Last Modified: 10/24/2014
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