Parasitism

Coastal Furbearers Catch A New Bug

Citation

Shanebeck, K. M., Thacker, D. C., & Lagrue, C. (2022). Corynosoma strumosum (Acanthocephala) infection in marine foraging mink (Neogale vison) and river otter (Lontra canadensis) and associated peritonitis in a juvenile mink. Parasitology International, 102579. https://doi.org/10.1016/j.parint.2022.102579

 

(Un)picky Eaters

Northern American minks (Neogale vision) and river otters (Lontra canadensis) are both predatory marine animals that eat lots of fish and intertidal organisms. They both have generalist diets, meaning they’ll scarf down pretty much anything you put in front of them, and this makes them easy to cook for, but it also exposes them to a wide variety of parasites. 

A North American mink (Neogale vision) Credit: Ekytza- Wiki Commons
Adorable River Otters (Lontra Canadensis)
Credit: Dmitry Azovtsev

Meet the Parasite

Corynosoma strumosum is a very common and widespread parasite among seals that causes debilitating inflammation of the small intestine, and can impact the survival of its host. This can create consequences much bigger than having to cancel plans after too much spicy Indian curry. This parasite can wreak serious havoc on the hosts’ health. Seals are its primary host, but this particular parasite is closely related to Corynosoma endhydri, a parasite that infects sea otters.

Attack of the Worms!

Until recently, reports of C. strumosum were largely contained to seal hosts. However in 2021, Canadian fur trappers caught two minks and a river otter infected with an unknown disease. The carcasses were sent to scientists at the University of Alberta, who eventually were able to confirm the first reported case of C. strumosum in those animals.

A related Corynosoma worm
Credit: Dr. Neil Campbell, University of Aberdeen

The only infected juvenile mink was the most serious case. Dissection of this mink revealed five individual C. strumosum in its abdominal cavity, a veritable wormapalooza compared with the adults. It also showed perforation, or penetration, of the intestinal wall, meaning the parasite spread past the abdominal cavity and into the small intestine. The juvenile mink showed signs of emaciation, blood loss, and anemia, all as a result of this infection, and likely the direct cause of the mink’s death.

 

The parasites were identified based on their morphology and genetics. The scientists extracted DNA from 8 individual parasitic worms, and this DNA was amplified and then compared to DNA using known DNA sequences from an online database. DNA sequencing relies on targeting a specific gene that other scientists have sequenced, and comparing that sequence to the DNA you are trying to identify. This process allowed the scientists to confirm the parasite was C. strumosum.

Who’s Worm-Proof?

The juvenile mink died because C. strumosum perforated the intestine wall and caused sepsis, but this didn’t happen in the infected adults. Why was the juvenile so vulnerable? The authors of the paper saw a much higher number of worms in the juvenile than the adults, so maybe worm counts are linked to the parasite’s ability to get through the intestine wall. It is also possible that the juvenile’s younger age left it more vulnerable to C. strumosum.

A Wormy Future for Furbearers?

Parasites can cause a lot of damage to a marine ecosystem. Their ability to incapacitate and kill certain species can shift community structure and alter local food webs. The parasite in this paper has been found in minks and river otters, ecologically significant animals that are not normal hosts for C. strumosum. Yet the authors note that wild minks and river otters seem to be biologically ideal hosts for this parasite, and their generalist diet of marine fish means that they have a lot of potential for exposure. The worm is also closely related to similar parasitic worms that routinely infects other otter species, which implies that this parasite may be well positioned to do serious damage on these species. The spread of parasites to new hosts requires close monitoring to understand the overall health of these furry foragers and enable more effective management and conservation strategies.

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