Versteria species infections and implications for human health

The Versteria genus includes two species of tapeworm, the Versteria mustelae, and an unnamed species that has been implicated in the fatal infections of various intermediate host species across North America. Given that relatively little is known about this unnamed species, researchers are interested in further characterizing the tapeworm and the infections they cause.

Performing necropsies on the hosts that die as a result of Versteria infections is one way to learn more about the mysterious worm. These necropsies enable scientists to see the worm’s larvae as well as the damage inflicted by the parasite on the body of the host. 

For this study, a research team, including CEID’s Michael Yabsley and Alec Thompson, performed a necropsy on a muskrat suspected to have died from a Versteria species infection to learn more about the circumstances of the animal’s death.

The necropsy revealed that the muskrat’s liver was covered in dozens of cysts containing parasitic worm larvae, with the lungs, kidneys, spleen, ovaries, brain and gastrointestinal tract also carrying larval cysts. In addition to the cysts, there was tissue loss and mild inflammation in several of the organs.

During the necropsy, the research team also extracted DNA from the cysts to examine the novel Versteria species more closely and develop an evolutionary tree for the genus. The researchers were able to determine the relative placement of this unidentified species on the evolutionary tree by comparing the DNA obtained from the cysts to the DNA of other specimens in the genus.

They found that the Versteria specimen responsible for the infection of the muskrat was genetically most similar to specimens found in mink in Oregon and in ermine in Colorado, and it’s also closely related to specimens found in one captive orangutan and humans. The reports of Versteria infection in humans included three cases that resulted in death.

The conclusion that this species is genetically closely related to specimens that have caused death in humans indicates that identification needs to occur more frequently and accurately. The genetic relation indicates there could be potential for a zoonotic spillover and outbreak of Versteria infection among humans. Zoonotic spillover occurs when a disease normally infecting animals is transmitted to humans. 

Future research should expand on existing knowledge of relationships between the different specimens of Versteria and identification options in order to better inform understanding of the potential for a serious threat of infection and transmission in humans.

To learn more about this study, click here.

By Amanda Budd