Parasites, contaminants, and body condition of muskrat (Ondatra zibethicus) in Alberta, Canada.

Environmental contamination from anthropogenic activities threatens ecosystem and wildlife health, yet interactions between contaminant exposure and biological stressors such as parasitic infections remain poorly understood. Muskrat (Ondatra zibethicus Linnaeus, 1766) are ecologically important furbearers in aquatic ecosystems serving as sentinel species and providing resources for Indigenous communities. We investigated helminth parasites and trace metals in 41 adult muskrat from Alberta's Lac La Biche region, an area influenced by oil sands operations, hypothesizing that parasite burdens and non-essential trace metal concentrations would negatively affect body condition. All individuals harbored helminths (mean species richness: 3.29 ± 1.21), with gastrointestinal trematodes dominating infections. Quinqueserialis quinqueserialis (Barker and Laughlin 1911) (78% prevalence) and Plagiorchis proximus Barker, 1915 (71%) were most prevalent, while larval Versteria rafei Shanebeck, Bennett, Green, Lagrue, and Presswell, 2024, a zoonotic cestode, infected 44% of animals, a substantially higher prevalence than previously reported. Trace metal analysis revealed elevated bismuth, barium, gallium, iron, and strontium concentrations. High trematode intensity, mercury, and strontium were associated with reduced fat stores, while arsenic and mercury were linked to lower body mass index. Arsenic was also associated with increased renal somatic index, suggesting potential nephrotoxic stress. These findings highlight cumulative impacts of biological and chemical stressors and the importance of integrated wildlife health monitoring in industrial landscapes.