Cooperative Fish and Wildlife Research Units Program: Pennsylvania
Education, Research and Technical Assistance for Managing Our Natural Resources

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.


The Taeniidae 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, Versteria, 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 Versteria infection in a muskrat (Ondatra zibethicus) 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 Versteria 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 Versteria 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.