A total of 21 species of parasitic helminths was recovered from wild and captive caribou. Gastrointestinal nematodes were represented by eight species of Ostertagiinae, four species of Nematodirinae, Trichostrongylus axei, T. vitrinus, Oesophagostomum venulosum, Trichuris ovis, Skrjabinema sp., and Capillaria sp. Other helminths included Dictyocaulus viviparus, Setaria yehi, and Moniezia sp. Nematodirus odocoilei, a common parasite of Odocoileus spp. is reported from caribou for the first time. Ostertagia leptospicularis is reported from North America for the first time. Illustrations and diagnostic keys are provided for the eggs, infective larvae, and adults of the gastrointestinal nematodes recovered from caribou.
The synlophe for specimens of Nematodirus odocoilei from deer (Odocoileus hemionus) and woodland caribou (Rangifer tarandus caribou) is characterized. In the cervical region, at the level of the cervical papillae, there are 36–42 and 38–47 ridges of variable height in males and females, respectively. Sixteen ridges extend to the cephalic expansion. In males, 34–40 ridges occur at midbody, and the synlophe extends posteriad to within 50 μm of the prebursal papillae. In females, 36–42 ridges occur at midbody; the maximum number of ridges occurs posterior to the vulva (50) with a decrease again posteriad. The synlophe is continuous and extends to the caudal extremity of females. Based on concepts of parasite–host biogeography, both host switching and coevolution appear as determinants in the relationships of Nematodirus spp. and cervids. An evaluation of parasite morphology and host–parasite biogeography suggests that in the plesiomorphic condition the synlophe is composed of a high number of ridges as exemplified by Nematodirus spp. from cervids and neotropical camelids.
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