(Submitted photo/Frank Crockett)

By Brady Bateman

Parasitic Disease

Large population of canids infected with tapeworm capable of causing “tumour-like” disease

Jul 26, 2019 | 5:12 PM

A small tapeworm capable of causing a “tumour-like disease” in humans is becoming more common in carnivorous animals with up to 70 per cent of coyotes tested near the P.A. area to be infected.

Echinococcus multilocularis is normally found in the small intestines of wild canids such as foxes, wolves, and coyotes. Problems arise when species that are not part of the parasite’s normal life cycle accidentally ingest eggs found in the feces of an infected animal – such as dogs, cats or humans.

Although the disease caused by the tapeworm can be potentially fatal in humans, cases involving human infection are rare according to Trent Bollinger, regional director of the Canadian Wildlife Health Cooperative.

“You would basically have to somehow ingest the feces of an infected animal. If a pet picks it up by feeding on a rodent intermediate host, they can shed the eggs of the parasite in their feces, and if you came into contact with those eggs and ingest them, you could come down with the disease,” Bollinger said.

“It’s certainly not very common for people to be infected with this parasite. In the past it was more of an issue for people such as trappers. People should be aware of it, but it’s not something that people need to be overly worried about.”

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Once the parasite has been ingested by an intermediate host, grape-like cysts form which are the larval form of the tapeworm. These parasitic cysts initially become established in the liver but as the infection progresses, the cysts can spread throughout the body.

These infected individuals develop the larval stage of the parasite. These cysts then cause a disease called alveolar echinococcosis (AE).

“Out of the coyotes that we tested in the Prince Albert, Battlefords and Saskatoon area, around 60 to 70 per cent of the animals were positive for the parasite,” Dr. Emily Jenkins, a professor at the Veterinary College at the University of Saskatchewan said. She has spent roughly 10 years studying echinococcus multilocularis.

“We’ve also had a confirmed human case in which my lab was involved doing the identification of the parasite, so we are definitely very concerned in Saskatchewan and keeping a close eye on human cases as well.”

Jenkins added it is difficult to confirm human cases as there is no official surveillance for the tapeworm at the moment. She added the case her lab was involved with in 2018 is the first locally acquired case in Saskatchewan.

More than 200 coyotes were sampled as a part of Jenkins study in the winter of 2018, with roughly 70 per cent of animals tested being infected.

According to Jenkins, those at the largest risk of acquiring the disease are not hunters and trappers, but anyone who has ingested wild berries or mushrooms without being properly cleaned, or those who have ingested unfiltered water from natural sources.

“We’re seeing a surprising and increasing amount of canine cases where the parasite takes over the liver of the dog and behaves as a tumour. So we as veterinarians are quite alarmed to see an increase like this in the number of canine cases of this disease,” Jenkins said.

“We try to advise people that have dog, which have access to eating wild rodents, to be very proactive in their de-worming, with monthly de-worming to protect human health, and to protect dogs from getting the liver form of the parasite.”

Individuals with a supressed immune system are at a higher risk of having the parasite. Jenkins added the testing and surveillance needed to get on top of the growing number of cases is not currently available.

“Saskatchewan is going to start seeing more human cases. The biggest issue is that most physicians trained in North America have no idea to look for this, or to even keep it on their radar as a potential diagnosis,” Jenkins said.

“The disease used to have a 90 per cent case fatality disease. That is a very different number now because we have modern methods of surgery and medical management, chemotherapy essentially. The real key for a good outcome is early detection, so if your doctor figures out what you have very soon … your outcome will be much, much better.”

According to the Western College of Veterinary Medicine there had been no documented cases of AE in Canadian dogs up until 2009. Since then, veterinarians have identified cases in British Columbia, Alberta, Saskatchewan, Manitoba and Ontario.

The tapeworm was initially discovered in wildlife in Western Canada in 2012, with the first human case of alveolar echinococcosis confirmed in 2013 according to a study by the University of Calgary’s Faculty of Veterinary Medicine (UCVM).

The disease develops slowly over several years, causing multiplying lesions in the body, especially the liver, and is potentially fatal if left undiagnosed and left to spread to other organs.

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Brady.bateman@jpbg.ca

On Twitter: @TheDigitalBirdy