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Niedringhaus, K.D, L.S. Ganoe, M. Lovallo, W.D. Walter, M.J. Yabsley, J.D. Brown. 2022. Fatal infection by Versteria sp. in a muskrat (Ondatra zibethicus) with implications for human health. Journal of Veterinary Diagnostic Investigations 34(2): 314–318.
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Abstract
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March 2022
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The <i>Taeniidae</i> tapeworms are a family of helminths that have a similar life cycle with intermediate hosts developing characteristic cysts in visceral organs. Recently, a new genus in this family, <i>Versteria,</i> has been implicated as the cause of severe morbidity and mortality in humans and animals in North America. This report describes a case of fatal <i>Versteria</i> infection in a muskrat (<i>Ondatra zibethicus</i>) which has not been previously reported to develop disease associated with infection. Postmortem examination revealed widespread tissue loss and replacement by solid-bodied cestode larvae with minimal adjacent inflammation in many visceral organs, most severe in the lungs, liver, and brain. Characteristic morphological features via histology included multiple cephalic structures and short rostellar hooklets, which are characteristic for the genus. Genetic characterization confirmed the cestode as being an undescribed lineage of <i>Versteria</i> that has been implicated as the cause of severe morbidity and mortality in humans and non-human primates in North America. Considering the zoonotic significance of this pathogen, this report expands on the limited literature regarding disease caused by <i>Versteria </i>and emphasizes the need to identify the causative tapeworm more accurately, especially in rodent intermediate hosts as all previous reports do not have molecular confirmation of species.
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Ganoe, L.S., J.D. Brown, M.J. Yabsley, M.J. Lovallo, and W.D. Walter. 2020. A review of pathogens, diseases, and contaminants of muskrats (Ondatra zibethicus) in North America. Frontiers in Veterinary Science 7:233. doi: 10.3389/fvets.2020.00233.
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Abstract
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May 2020
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Over the last 50 years, significant muskrat (<i>Ondatra zibethicus</i>) 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 129 articles from 1915-2019were 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 disease over a century that has observed significant population declines throughout the species’ range in North America. Such data provides baseline data for understanding the potential role of disease in these declines. In addition, these data highlight critical knowledge gaps that warrant future research efforts.
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Ganoe, L.S., J.D. Brown, M.J. Lovallo, M.J. Yabsley, K.B. Garrett, A.T. Thompson, R.H. Poppenga, M.G. Ruder, and W.D. Walter. 2021. Surveillance for diseases, pathogens, and toxicants of muskrat (Ondatra zibethicus) in Pennsylvania and surrounding regions. PlosONE 16(12):e0260987.
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Abstract
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December 2021
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Using diagnostic data and contemporary sampling efforts, we conducted surveillance for a diversity of pathogens, toxicants, and diseases of muskrats (<i>Ondatra zibethicus</i>). Between 1977 and 2019, 26 diagnostic cases were examined from Kansas and throughout the Southeast and Mid-Atlantic, USA. We identified multiple causes of mortality in muskrats, but trauma (8/26), Tyzzer’s disease (5/6), and cysticercosis (5/26) were the most common. We also conducted necropsies, during November 2018 - January 2019 Pennsylvania muskrat trapping season, on 380 trapper-harvested muskrat carcasses after the pelt was removed. Tissue samples and exudate were tested for presence of or exposure to a suite of pathogens and contaminants. Gastrointestinal tracts were examined for helminths. Intestinal helminths were present in 39.2% of necropsied muskrats, with <i>Hymenolepis</i> spp. (62%) and echinostome spp. (44%) being the most common. Molecular testing identified a low prevalence of infection with <i>Clostridium piliforme </i>in the feces and <i>Sarcocystis</i> spp. in the heart. We detected a low seroprevalence to <i>Toxoplasma gondii</i> (1/380)<i>.</i> No muskrats were positive for <i>Francisella tularensis </i>or <i>Babesia </i>spp. Cysticercosis was detected in 20% (5/26) of diagnostic cases and 15% (57/380) of our trapper-harvested muskrats. Toxic concentrations of arsenic, cadmium, lead, or mercury were not detected in tested liver samples. Copper, molybdenum, and zinc concentrations were detected at acceptable levels comparative to previous studies. Parasite intensity and abundance were typical of historic reports; however, younger muskrats had higher intensity of infection than older muskrats which is contradictory to what has been previously reported. A diversity of pathogens and contaminants have been reported from muskrats, but the associated disease impacts are poorly understood. Our data are consistent with historic reports and highlight the wide range of parasites, pathogens and contaminants harbored by muskrats in Pennsylvania. The data collected are a critical component in assessing overall muskrat health and serve as a basis for understanding the impacts of disease on recent muskrat population declines.
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