Brett T. Elkin

The Arctic as a model for anticipating, preventing, and mitigating climate change impacts on host-parasite interactions.

Climate change is influencing the structure and function of natural ecosystems around the world, including host-parasite interactions and disease emergence. Understanding the influence of climate change on infectious disease at temperate and tropical latitudes can be challenging because of numerous complicating biological, social, and political factors. Arctic and Subarctic regions may be particularly good models for unraveling the impacts of climate change on parasite ecology because they are relatively simple systems with low biological diversity and few other complicating anthropogenic factors. We examine some changing dynamics of host-parasite interactions at high latitudes and use these to illustrate a framework for approaching understanding, preventing, and mitigating climate change impacts on infectious disease, including zoonoses, in wildlife.

“Emerging” Parasitic Infections in Arctic Ungulates

Abstract Important drivers for emergence of infectious disease in wildlife include changes in the environment, shrinking habitats or concentration of wildlife, and movement of people, animals, pathogens, or vectors. In this paper we present three case-studies of emerging parasitic infections and diseases in ungulates in the Canadian north. First we discuss climate warming as an important driver for the emergence of disease associated with Umingmakstrongylus pallikuukensis, a nematode lungworm of muskoxen. Then we examine how Protostrongylus stilesi, the sheep lungworm, emerged (or re-emerged) in muskoxen after re-introduction of this host into its historical range made it sympatric with Dalls sheep. Finally, we consider Teladorsagia boreoarcticus, a newly described and common abomasal nematode of muskoxen that is emerging as a disease-causing parasite and may be an important regulator for muskox populations on Banks Island, Northwest Territories. These and other arctic host-parasite systems are exquisitely tuned and constrained by a harsh and highly seasonal environment. The dynamics of these systems will be impacted by climate change and other ecological disruptions. Baseline knowledge of parasite biodiversity and parasite and host ecology, together with predictive models and long-term monitoring programs, are essential for anticipating and detecting altered patterns of host range, geographic distribution, and the emergence of parasitic infections and diseases.

Dogs as Sources and Sentinels of Parasites in Humans and Wildlife, Northern Canada

A minimum of 11 genera of parasites, including 7 known or suspected to cause zoonoses, were detected in dogs in 2 northern Canadian communities. Dogs in remote settlements receive minimal veterinary care and may serve as sources and sentinels for parasites in persons and wildlife, and as parasite bridges between wildlife and humans.

Integrated approaches and empirical models for investigation of parasitic diseases in northern wildlife.

A decade of research has yielded a multidisciplinary approach for detection, prediction, and potential mitigation measures.

Geographic distribution of the muscle-dwelling nematode Parelaphostrongylus odocoilei in North America, using molecular identification of first-stage larvae.

Molecular identification of dorsal-spined larvae (DSL) from fecal samples indicates that the protostrongylid parasite Parelaphostrongylus odocoilei occupies a broader geographic range in western North America than has been 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). The DSL were recovered from populations of thinhorn sheep south, but not north, of the Arctic Circle, and they were not recovered from any of the bighorn sheep populations that we examined. In total, DSL were recovered from 20 locations in the United States and Canada (Alaska, Yukon Territory, Northwest Territories, British Columbia, Alberta, and California). The 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. The ITS2 sequences were markedly different between Parelaphostrongylus and other protostrongylid genera. Smaller fixed differences served as diagnostic markers for the 3 species of Parelaphostrongylus. The 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. This work combines extensive fecal surveys, comparative morphology, and molecular diagnostic techniques to describe comprehensively the host associations and geographic distribution of a parasitic helminth.

Parasites in Ungulates of Arctic North America and Greenland: A View of Contemporary Diversity, Ecology, and Impact in a World Under Change

Parasites play an important role in the structure and function of arctic ecosystems, systems that are currently experiencing an unprecedented rate of change due to various anthropogenic perturbations, including climate change. Ungulates such as muskoxen, caribou, moose and Dalls sheep are also important components of northern ecosystems and are a source of food and income, as well as a focus for maintenance of cultural traditions, for northerners. Parasites of ungulates can influence host health, population dynamics and the quality, quantity and safety of meat and other products of animal origin consumed by people. In this article, we provide a contemporary view of the diversity of nematode, cestode, trematode, protozoan and arthropod parasites of ungulates in arctic and subarctic North America and Greenland. We explore the intricate associations among host and parasite assemblages and identify key issues and gaps in knowledge that emerge in a regime of accelerating environmental transition.

Protostrongylus stilesi (Nematoda: Protostrongylidae): Ecological Isolation and Putative Host-Switching Between Dall's Sheep and Muskoxen in a Contact Zone

Abstract The occurrence of Protostrongylus stilesi in a population of introduced muskoxen, Ovibos moschatus wardi, on the Arctic Coastal Plain, Yukon Territory (YT) and Northwest Territories (NT), Canada, is consistent with a contemporary colonization event from Dalls sheep, Ovis dalli dalli, which indicates that host specificity may be ecologically based and contextual for this parasite. Colonization of muskoxen by P. stilesi may be a predictable event in zones of sympatry with Dalls sheep; exposure to infection may coincide with occupation of winter ranges of Dalls sheep by muskoxen during the summer season. Disruption of contemporary ecological isolating barriers can result from anthropogenically or climatologically driven habitat perturbation, and result from management practices that influence the distribution of ungulate hosts. Thus, if zones of contact become more extensive or the temporal limits on allopatry are relaxed, we may observe increasing instances of host switching by parasites or pathogens at the interface of newly emerging ecotones. Impacts to northern systems linked to climatologically and anthropogenically driven global change and the effects of management must be tracked within the context of biodiversity survey and inventory and archival collections, as foundations for monitoring ecosystem-level perturbations. A developing interface for muskoxen, wild sheep, and parasites along the Mackenzie River ecotone represents a natural model or field laboratory to examine these processes. Additonally, lungworms, Protostrongylus spp., had not been reported in muskoxen, and a new geographic record for this nematode was established in Dalls sheep from the northern Richardson Mountains, NT.

Giardia assemblage A: human genotype in muskoxen in the Canadian Arctic

As part of an ongoing program assessing the biodiversity and impacts of parasites in Arctic ungulates we examined 72 fecal samples from muskoxen on Banks Island, Northwest Territories, Canada for Giardia and Cryptosporidium. Cryptosporidium spp. were not detected, but 21% of the samples were positive for Giardia. Sequencing of four isolates of Giardia demonstrated G. duodenalis, Assemblage A, a zoonotic genotype.

New Host and Geographic Records for Two Protostrongylids in Dall's Sheep

Biodiversity survey and inventory have resulted in new information on the distribution of Protostrongylidae in Dalls sheep (Ovis dalli dalli) from the Northwest Territories (NT, Canada) and from Alaska (AK, USA). In 1998, Parelaphostrongylus odocoilei adults were found for the first time in the skeletal muscles of Dalls sheep in the Mackenzie Mountains (NT). Adult P. odocoilei were associated with petechial and ecchymotic hemorrhages and localized myositis; eggs and larvae in the lungs were associated with diffuse granulomatous pneumonia. Experimental infections of the slugs Deroceras laeve and Deroceras reticulatum with dorsal-spined first-stage larvae assumed to be P. odocoilei, from ground-collected feces from Dalls sheep in the Mackenzie Mountains, yielded third-stage larvae by at least 28 (in D. laeve) and 48 (in D. reticulatum) days post-infection. Third-stage larvae emerged from D. laeve between days 19 and 46 post-infection and emergence occurred both at room temperature and at 10 to 12 C. Protostrongylus stilesi were definitively identified from the lungs of Dalls sheep collected in the Mackenzie Mountains, NT in 1998. Specimens collected from sheep in the Mackenzie Mountains, NT in 1971–72, and the Alaska Range, AK in 1972 were also confirmed as P. stilesi. Lung pathology associated with adults, eggs, and larvae of P. stilesi was similar to that described in bighorn sheep (Ovis canadensis). Concurrent infections with P. odocoilei and P. stilesi in a single host have not been previously reported.

Prevalence of Toxoplasma gondii Antibodies in Barren-Ground Caribou (Rangifer tarandus groenlandicus) From the Canadian Arctic

Prevalence of antibodies to Toxoplasma gondii was determined in 147 barren-ground caribou (Rangifer tarandus groenlandicus) from 5 herds in the Northwest Territories and Nunavut, northern Canada, by the modified agglutination test (MAT). In the mainland herds (Bluenose, Bathurst, and Beverly), antibodies were found in 43 (37%) of 117 caribou, and MAT titers were 1:25 in 10, 1:50 in 24, and 1:500 in 9. In the island herds, only 1 (4.3%) of 23 animals sampled from the North Baffin Island herd was positive (titer = 1:25) and no antibodies were detected in 7 caribou from the Dolphin and Union herd. The high prevalence of antibodies to T. gondii in the mainland caribou herds indicates that caribou meat may contain viable T. gondii.