CLIMATE CHANGE AND EPIDEMIOLOGY OF PROTOSTRONGYLID NEMATODES IN NORTHERN ECOSYSTEMS: PARELAPHOSTRONGYLUS ODOCOILEI AND PROTOSTRONGYLUS STILESI IN DALL'S SHEEP (OVIS DALLI DALLI)

Authors: JENKINS, E - U SASKATCHEWAN,CANADA; VEITCH, A - WILDLIFE MGMT, CANADA; KUTZ, S - U SASKATCHEWAN,CANADA; Hoberg, Eric; POLLEY, L - U SASKATCHEWAN, CANADA

Submitted to: Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/18/2005
Publication Date: 1/30/2006
Citation: Jenkins, E.J., Veitch, A.M., Kutz, S.J., Hoberg, E.P., Polley, L. 2006. Climate change and epidemiology of protostrongylid nematodes in northern ecosystems: parelaphostrongylus odocoilei and protostrongylus stilesi in dall's sheep (ovis dalli dalli). Parasitology 132:387-401.

Interpretive Summary: Climate warming is predicted to have a major impact on the distribution and life history of parasites in ungulates. We currently have limited information to develop models for patterns of development of larval stages, and for the dynamics involved in survival and transmission between hosts. We describe the epidemiology of two protostrongylid parasites, Parelaphostrongylus odocoilei and Protostrongylus stilesi, in Dall’s sheep (Ovis dalli dalli) from the Mackenzie Mountains, Northwest Territories, Canada (65º N; 128º W). Peak numbers of first-stage larvae of both protostrongylids were shed by Dall’s sheep on their winter range from March-May, and peak numbers of third-stage larvae of P. odocoilei were available in experimentally-infected gastropod intermediate hosts in August-September. The majority of transmission likely occurs on the winter range, with infection of gastropods when they emerge from hibernation in spring, and infection of Dall’s sheep upon their return in fall. We validated a degree day model for temperature-dependent development of larval P. odocoilei in gastropods, and applied this model to describe and predict spatial and temporal patterns in development of P. odocoilei and P. stilesi. Temperature-dependent larval development is not currently limiting northward range expansion of P. odocoilei into naïve populations of Dall’s sheep in the Arctic. In Subarctic regions where both P. odocoilei and P. stilesi are endemic, the length of the parasite “growing season” and amount of warming available for parasite development has increased over the last 50 years. With climate warming, the seasonal window for transmission will be significantly extended, possibly leading to amplification of parasite populations and disease outbreaks in host populations. Detailed biological studies are necessary dealing with a variety of complex host-parasite system to formulate accurate models for the impact of directional warming in northern and temperate systems.

Technical Abstract: We describe the epidemiology of two protostrongylid parasites, Parelaphostrongylus odocoilei and Protostrongylus stilesi, in Dall’s sheep (Ovis dalli dalli) from the Mackenzie Mountains, Northwest Territories, Canada (65º N; 128º W). Peak numbers of first-stage larvae of both protostrongylids were shed by Dall’s sheep on their winter range from March-May, and peak numbers of third-stage larvae of P. odocoilei were available in experimentally-infected gastropod intermediate hosts in August-September. The majority of transmission likely occurs on the winter range, with infection of gastropods when they emerge from hibernation in spring, and infection of Dall’s sheep upon their return in fall. We validated a degree day model for temperature-dependent development of larval P. odocoilei in gastropods, and applied this model to describe and predict spatial and temporal patterns in development of P. odocoilei and P. stilesi. Temperature-dependent larval development is not currently limiting northward range expansion of P. odocoilei into naïve populations of Dall’s sheep in the Arctic. In Subarctic regions where both P. odocoilei and P. stilesi are endemic, the length of the parasite “growing season” and amount of warming available for parasite development has increased over the last 50 years. With climate warming, the seasonal window for transmission will be significantly extended, possibly leading to amplification of parasite populations and disease outbreaks in host populations.