Variation in the intensity and prevalence of macroparasites in migratory caribou: a quasi-circumpolar study

Abstract

Comparative studies across time and geographical regions are useful to improve our understanding of the health of wildlife populations. Our goal was to study parasitism in migratory caribou (Rangifer tarandus (L., 1758)) of North America and Greenland. A total of 1507 caribou were sampled across 12 herds to assess seven of their main helminth and arthropod macroparasites between 1978 and 2010. We sought to determine which factors such as sex, age class, herd size, and season best explained the prevalence and intensity of those parasites. Intensity of warble fly (Hypoderma tarandi (L., 1758)) larvae increased with age for males, whereas the opposite was observed in females. Prevalence of giant liver flukes (Fascioloides magna (Bassi, 1875) Ward, 1917), tapeworm Taenia hydatigena Pallas, 1766, and nose bot fly (Cephenemyia trompe (Modeer, 1786)) larvae was higher in adults than in calves. Prevalence of F. magna and T. hydatigena was higher at high herd size than at lower herd size. Greenland herds had the lowest prevalence of T. hydatigena and of the tapeworm Taenia krabbei Moniez, 1879, a higher intensity of H. tarandi, and a higher prevalence of C. trompe than the other herds. Of the herds from Quebec and Labrador, the Rivière-George herd had a higher prevalence of F. magna than the Rivière-aux-Feuilles herd. Our research provides the first comparative survey of these parasites of caribou across a broad spatial–temporal range.

Multi-pathogen serological survey of migratory caribou herds: A snapshot in time

“…With respect to pathogen diversity in the Quebec and Labrador herds, differences in the parasitological fauna compared to barren-ground caribou have previously been described and likely link back to their historical biogeography [32,64]. Similar differences in pathogens detected through serology are also expected.…”

“…Herd was an important covariate for predicting both alphaherpesvirus and pestivirus seroprevalence, although no distinct pattern could be discerned. Differences among herds and regions can have arisen as a result of ecological, demographic, behavioural and evolutionary factors [32,63,64] but sampling regimes may also have influenced results. Historical biogeography could explain some differences in observed seroprevalence among herds.…”

“…Serological surveys and other pathogen studies involving Rangifer began to enter the literature around the 1970s and reported prevalences of various pathogens that could affect herd and human health (for example; [32][33][34][35]). However, many herds remain unsampled or undersampled and baselines are still incomplete.…”

Observed and predicted effects of climate change on Arctic caribou and reindeer

“…On summer ranges, increasing temperatures will likely lead to longer growing seasons, increases in plant productivity, and an earlier onset of spring, all of which could increase Rangifer body condition and reproductive success by shortening the winter period of food limitation, providing earlier access to forage (and thus offsetting the costs of parturition and lactation), and generally increasing the quantity and period of available forage (Tews et al 2007a;Cebrian et al 2008;Helle and Kojola 2008;Tveraa et al 2013;Veiberg et al 2016). However, this same increase in temperature will also likely increase insect harassment; provide opportunity for predators, potential competitor species, parasites, and diseases that have historically been restricted to more southerly ranges to expand northward; and alter plant community composition to be dominated by potentially less nutritious species (Sharma et al 2009;Witter et al 2012a;Kutz et al 2013;Thompson and Barboza 2014;Simard et al 2016). Additionally, all Rangifer populations may not respond positively to the advancement of spring (Post and Forchhammer 2008;Kerby and Post 2013).…”

“…Warming temperatures are predicted to alter the geographic distribution, transmission rates, host-parasite assemblages, and life-cycle phenologies of pathogens (Harvell et al 2002;Kutz et al 2004;Kutz et al 2005;Polley and Thompson 2009;Simard et al 2016), and in some cases, the northern expansion of parasitic species have already been observed (Laaksonen et al 2010;Kutz et al 2013). Arctic ecosystems are vulnerable to invasions by exotic species, including parasites, due to a number of factors.…”