A Survey for Echinococcus in Saskatchewan Coyotes
We might be the only people in Canada happy to have a cold February. As in “high of -20 C” cold, for weeks on end. That’s because we received a trailer full of 200 coyote carcasses trapped in Saskatchewan last February, and had nowhere to keep them frozen while we processed them.
This was part of a research project on Echinococcus multilocularis, a tapeworm that normally transmits between wild canids (coyotes and foxes) and wild rodents (voles and deer mice). Recent cases in dogs and people in Canada have raised concerns that this wildlife parasite is spreading and showing more potential to cross species borders.
To determine how common the parasite is in coyotes in Saskatchewan, we contacted the local trappers association, who delivered skinned carcasses which would otherwise have simply been discarded. Coyotes were trapped from all around the west central region of the province, in an area roughly bounded by the towns of North Battleford, Prince Albert, and Saskatoon. Hence the trailerful of frozen coyotes sitting in the parking lot…
We had to process the carcasses before thaw – and to do that we enlisted student members of the local Wildlife Disease Association chapter. As veterinary students, they had keen enthusiasm, good anatomical knowledge, and best of all, they were vaccinated against rabies. Although trapped coyotes are extremely unlikely to have rabies, the rules are that anyone handling wild canids should be vaccinated, and wear protective masks and clothing.
The students were troopers, photographing the teeth of each carcass for aging, collecting heart blood and chest fluid for testing for antibodies (serology), muscles for testing for a parasitic roundworm called Trichinella, and intestines for tapeworm testing. Students didn’t open the intestines, because eggs of Echinococcus are immediately infective for people. Instead, the intestines were frozen at even-colder-than-a-Saskatchewan-winter-temperature (-80C) for at least 3 days. This is one of few things known to kill these hardy eggs.
Then, in the summer of 2018, two undergraduate veterinary students, Joy Wu and Mila Bassil, processed the intestines to recover the tiny, but deadly, tapeworms. This is a tedious, time consuming, and smelly procedure, which is why they spent many hours in a fume hood, without human contact. But their efforts were rewarded…
Much to our surprise, over 70% of the coyotes were infected with Echinococcus, and thus far it all seems to be E. multilocularis, rather than the more benign E. canadensis that cycles between coyotes and wild cervids like moose, elk, or caribou. This infection rate is more than double what we expected, based on previous studies in western Canada showing that 20-30% of coyotes were infected. This suggests a very high level of environmental contamination with eggs of E. multilocularis. And some of these coyotes were trapped just outside the Saskatoon city limits.
Finally, as part of graduate student Temitope Kolapo’s project and in collaboration with Dr Caroline Frey (Canadian Food Inspection Agency), samples from these coyotes will be used to develop better tests for the parasite in dogs, including fecal testing for the form harmful to people, and blood tests (serology) for the form that can be fatal in dogs. She will also compare the genetics of the parasite in coyotes, dogs, rodents, and people in Saskatchewan to determine how the parasite circulates in wildlife and spills over into people and pets. Finally, she will determine if the strain(s) of the parasite are home grown North American strains that have suddenly jumped the species barrier, or if recently introduced European strain(s) have colonized native wildlife and now pose a new threat to animal and human health.
And all this, from a trailer of frozen coyotes in the depths of February in Saskatchewan… this February, we are hoping the cold holds out, as we have a load of Arctic foxes coming…
This study and other research on wildlife parasites transmissible to people, is part of the Zoonotic Parasite Research Unit at the Western College of Veterinary Medicine, led by Emily Jenkins, who is affiliated with the Western/Northern region of the Canadian Wildlife Health Cooperative. This work is a collaboration with the Canadian Food Inspection Agency Centre for Food-borne and Animal Parasitology, and Aquila Diagnostics, and is funded by NSERC and the US National Center for Veterinary Parasitology.
Post by: Dr. Emily Jenkins