MUSKRATS (ONDATRA ZIBETHICUS) ARE COMPETENT INTERMEDIATE HOSTS OF ECHINOCOCCUS MULTILOCULARIS IN NORTH AMERICA.

The tapeworm Echinococcus multilocularis is an emerging pathogen of significance to human and animal health in Canada, yet little is known about key rodent intermediate hosts in local urban ecosystems. In Europe, invasive muskrats (Ondatra zibethicus) are an important indicator intermediate host species; however, the role of this semiaquatic rodent in the ecology of E. multilocularis is undetermined in the North American context. We examined 93 muskrats that were livetrapped in the spring of 2017 within Calgary, Alberta, Canada, for the presence of E. multilocularis infection. The objectives of this study were to 1) diagnose alveolar echinococcosis using macroscopic assessment, histopathology, and molecular analyses; 2) quantify infection severity; and 3) assess host demographic risk factors for infection. Macroscopic cysts consistent with alveolar echinococcosis were present in 24% of muskrats (22/93). Most individuals had hepatic cysts; however, cysts were also occasionally detected in the mesentery, reproductive organs, omentum, peritoneum, spleen, diaphragm, lung, or kidney. The mean number of cysts per liver was 2.1 (range, 1-4). We examined hepatic cysts from 18 individuals using histology; all had lesions compatible with alveolar echinococcosis. Protoscoleces, indicative of patent infections, were present in 14/18 (78%). No demographic risk factors (sex, body condition, body mass) were significantly associated with infection. Muskrats in the North American context are competent intermediate hosts with high infection prevalence and may play an important role in the ecology of this emerging parasite.

Spatial variation of mercury bioaccumulation in bats of Canada linked to atmospheric mercury deposition.

Wildlife are exposed to neurotoxic mercury at locations distant from anthropogenic emission sources because of long-range atmospheric transport of this metal. In this study, mercury bioaccumulation in insectivorous bat species (Mammalia: Chiroptera) was investigated on a broad geographic scale in Canada. Fur was analyzed (n=1178) for total mercury from 43 locations spanning 20° latitude and 77° longitude. Total mercury and methylmercury concentrations in fur were positively correlated with concentrations in internal tissues (brain, liver, kidney) for a small subset (n=21) of little brown bats (Myotis lucifugus) and big brown bats (Eptesicus fuscus), validating the use of fur to indicate internal mercury exposure. Brain methylmercury concentrations were approximately 10% of total mercury concentrations in fur. Three bat species were mainly collected (little brown bats, big brown bats, and northern long-eared bats [M. septentrionalis]), with little brown bats having lower total mercury concentrations in their fur than the other two species at sites where both species were sampled. On average, juvenile bats had lower total mercury concentrations than adults but no differences were found between males and females of a species. Combining our dataset with previously published data for eastern Canada, median total mercury concentrations in fur of little brown bats ranged from 0.88-12.78µg/g among 11 provinces and territories. Highest concentrations were found in eastern Canada where bats are most endangered from introduced disease. Model estimates of atmospheric mercury deposition indicated that eastern Canada was exposed to greater mercury deposition than central and western sites. Further, mean total mercury concentrations in fur of adult little brown bats were positively correlated with site-specific estimates of atmospheric mercury deposition. This study provides the largest geographic coverage of mercury measurements in bats to date and indicates that atmospheric mercury deposition is important in determining spatial patterns of mercury accumulation in a mammalian species.