COS 234-6 - Hidden stressors: parasites and pollutants a threat to river otter and mink in Western Canada

Abstract: Aquatic meso-carnivores are ideal sentinels for our freshwater and marine ecosystems. As apex predators in freshwater systems, they are at high risk for the bioaccumulation of pollutants and hosts to a variety of parasites. Studies investigating the populations of North American river otter (Lontra canadensis) and mink (Neovison vison) are limited, though they are integral parts of riparian ecosystems and are commercially trapped in Canada. Very little is known about their parasitic communities, and there is limited knowledge about how parasites may be influencing individual and population health and fitness. Previous reports have emphasized the danger of a variety of contaminants, including hydrocarbons around Albertan Oil Sands, and metals from mines in British Columbia, but our knowledge is still limited as to the prevalence and intensity of these threats. We investigated the parasites and pollutants of river otter (L. canadensis, n=155) and mink (N. vison, n=106) provided by licensed fur trappers in Alberta and British Columbia. We modeled the effects of parasites and pollutants on host energetic condition and potential link between parasitic infection and the bioaccumulation of pollutants in host livers. The goal of our study was to assess whether parasites and pollutants constitute a threat to aquatic meso-carnivores in Western Canada?

Necropsies of otter and mink recorded several parasites of concern, for both wildlife and human populations. Most prevalent was Alaria mustelae (Trematoda: Diplostomidae) which infected over 70% of animals, both mink and otter being competent definitive as well as paratenic hosts. Larval parasites were associated with subacute and chronic inflammation due to migration through the intestinal wall to other tissues and reduced energetic condition. Infections by larval Alaria alata have been reported to cause similar pathology in humans, while infections by A. mustelae have not previously been reported as a major threat to aquatic wildlife or people in Canada. Other zoonotic species of concern included infection by Versteria sp. (Cestoda: Taeniidae) which causes similar disease pathology to Echinococcus sp. and Toxoplasma gondii. Toxoplasma was also found in the brains of 30% of Albertan otters. Multiple pollutants of concern were identified, pollutant concentrations were influenced by both geographical and biological moderators, as well as mammal condition. Continued monitoring of aquatic meso-carnivores, especially those of commercial and indigenous importance like river otters and mink, is needed, as both parasites and pollutants may have serious implications for individual and population fitness, as well as the health of rural communities.