Global climate change is altering the ecology of infectious agents and driving the emergence of disease in people, domestic animals, and wildlife. We present a novel, empirically based, predictive model for the impact of climate warming on development rates and availability of an important parasitic nematode of muskoxen in the Canadian Arctic, a region that is particularly vulnerable to climate change. Using this model, we show that warming in the Arctic may have already radically altered the transmission dynamics of this parasite, escalating infection pressure for muskoxen, and that this trend is expected to continue. This work establishes a foundation for understanding responses to climate change of other host-parasite systems, in the Arctic and globally.

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Fecal samples are often the only feasible means to assess diversity of parasites in wildlife; however, definitive identification of egg or larval stages in feces by morphology is rarely possible. We determined partial sequences from the second internal transcribed spacer region (ITS-2) of nuclear ribosomal DNA for first-stage, dorsal-spined larvae (DSL) in feces from caribou ( Rangifer tarandus tarandus (L., 1758), Rangifer tarandus caribou (Gmelin, 1788), Rangifer tarandus grantii (Allen, 1902)), muskoxen ( Ovibos moschatus moschatus (Zimmermann, 1780), Ovibos moschatus wardi Lydekker, 1900), moose ( Alces alces gigas Miller, 1899 and Alces alces andersoni Peterson, 1952), and from the tissue of one slug ( Deroceras laeve (Müller, 1774)) in Arctic–Subarctic North America. A previously uncharacterized, genetically distinct species was recognized based on sequences of 37 DSL from 19 ungulate hosts and the slug. Sequence similarity among individuals of this novel species was 91%–100%. For many individual DSL, paralogues of ITS-2 were detected. ITS-2 sequences from the novel species were 72%–77% similar to those of Varestrongylus alpenae (Dikmans, 1935) and 51%–61% similar to those of other protostrongylids known in North American and some Eurasian ungulates. Results indicate a discrete lineage of an undescribed protostrongylid infecting muskoxen, caribou, and moose from Alaska to Labrador. Sympatric infections with Parelaphostrongylus andersoni Prestwood, 1972 were found in three caribou herds.

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.

Umingmakstrongylus pallikuukensis gen.nov. et sp.nov. is established for a protostrongylid nematode in muskoxen, Ovibos moschatus, from the Kitikmeot Region (central Arctic) of the Northwest Territories, Canada. It is distinguished from Cystocaulus and other Muelleriinae by characters that include the following: males: deeply incised, bilobed bursa, independent externodorsal rays, telamon composed of distal transverse plate, absence of falcate crurae, and spicules not distally split; females: absence of provagina; and first-stage larvae: presence of three cuticular folds on the tail. The great length of females (468 mm) and males (171 mm) is exceptional among the Protostrongylidae. Pathognomonic lesions include well-defined cysts dispersed through the lung tissue (maximum diameter 40 mm) containing adult and larval parasites in a dense matrix. Transmission involves a molluscan intermediate host, as indicated by experimental infections in the slug Deroceras reticulatum. The parasite is apparently restricted in its geographic distribution and has been found only in a population of muskoxen northwest of Coppermine, N.W.T. This may be indicative of a relictual host–parasite assemblage that has existed since the Pleistocene. The pathogenicity, high prevalence, and intensity of infection in the Coppermine herd suggest that the occurrence of U. pallikuukensis has implications for the management of muskoxen in the Holarctic region.

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

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 Dall's 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.

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