A Review of Pathogens, Diseases, and Contaminants of Muskrats (Ondatra zibethicus) in North America

Abstract

Over the last 50 years, significant muskrat (Ondatra zibethicus) harvest declines have been observed throughout North America. Several theories for the decline have been proposed, including increased parasite infections and disease within muskrat populations. No existing wholistic review of muskrat exposure to pathogens, contaminants, and diseases exists. To address this knowledge gap, we conducted a thorough review of existing literature on muskrat pathogens, contaminants, and diseases across their natural range. This review is comprised of 131 articles from 1915 to 2019 and from 27 U.S. states and 9 Canadian provinces. A wide diversity of contaminants, toxins, and pathogens were reported in muskrats, with the most common diseases being cysticercosis, tularemia, Tyzzer's disease, and biotoxin poisoning from cyanobacteria. This review provides a summary of muskrat pathogens, contaminants, and diseases over a century that has observed significant population declines throughout the species' range in North America. Such data provide a baseline for understanding the potential role of disease in these declines. In addition, these data highlight critical knowledge gaps that warrant future research efforts.

On the Helminth Fauna of the Muskrat (Ondatra zibethicus (Linnaeus, 1766)) in the Barnim District of Brandenburg State/Germany

“…The parasite spectrum of muskrats in Europe is relatively poor compared to that of North America. In publications on muskrat parasites from Canada and four US states 35 to 54 different endoparasite species were listed [ 9 ]. Examination of helminth fauna of muskrats in the state of Saxony-Anhalt in Germany ( n = 80) showed the presence of 15 and 13 different species, respectively [ 10 , 11 ].…”

Diversity of echinostomes (Digenea: Echinostomatidae) in their snail hosts at high latitudes

“…Trematodes from the family Echinostomatidae are influential players in freshwater ecosystems [ 81 ]. They can affect the larval trematode component community species composition in snail populations [ 83 , 87 ], they contribute substantially to energy flow in ecosystems [ 11 ], and they can cause diseases in humans and wildlife [ 43 , 130 ]. They are also considered effective competitors in combatting infection with schistosomes as the echinostome rediae actively feed on snail host tissue or other trematodes and can outcompete the less aggressive sporocysts [ 84 ].…”

Surveillance for diseases, pathogens, and toxicants of muskrat (Ondatra zibethicus) in Pennsylvania and surrounding regions

“…Nodules ranged in size (1 mm–4 cm diameter) and quantity (1 to dozens). Although the causative cestode was not definitively identified, four of the cysticercosis cases were caused by Hydatigera or Taenia species, which is historically the most common reported cause of cysticercosis in muskrats [ 5 ]. The fifth case of cysticercosis was in a muskrat from Pennsylvania in 2018.…”

“…Historically, muskrats have been documented as hosts and reservoirs for a wide range of pathogens and contaminants, however, the relationship between the prevalence of infection or contaminant exposure and muskrat health is poorly understood [ 5 ]. Many parasitological studies on muskrats only report prevalence of parasites without addressing body condition or health implications [ 6 – 8 ].…”