July 25, 2019

UCalgary research shows local emergence of a human disease caused by parasites in coyotes and foxes

Findings highlighted in letter to the editor of prestigious New England Journal of Medicine

Research led by the University of Calgary Faculty of Veterinary Medicine (UCVM) shows a strain of a tiny tapeworm that can make people seriously ill is now common in wildlife throughout Alberta.

In 2012, a parasitic tapeworm called echinococcus multilocularis (E. multilocularis) common in Europe, was first detected in wildlife in western Canada. A year later, the first human case of a tumour-like disease caused by the tapeworm, human alveolar echinococcosis (AE), was diagnosed. Since 2016, six more people in Alberta have been diagnosed with this potentially fatal disease, which develops slowly over several years and causes multiplying lesions in the body, usually in the liver. People with compromised immune systems are most at risk. Undetected, AE can spread to other organs and, if diagnosed too late, can be fatal.

The research, led by Dr. Alessandro Massolo, PhD, adjunct professor of wildlife health ecology at UCVM (now based at the University of Pisa in Italy where he’s an associate professor of behavioural ecology), Dr. Claudia Klein, DVM, PhD, UCVM associate professor, and Dr. Kinga Kowalewska-Grochowska of the University of Alberta, was shared in a letter to the editor in the latest issue of the New England Journal of Medicine.

“This evidence is the smoking gun that these AE cases are locally acquired, and they are caused by an invasive strain coming from Europe that has spread all over Alberta,” says Massolo. “So, this European strain is known to be very virulent for people, and now is everywhere in wildlife and even in dogs. From a public health perspective, to me is very relevant, because it has to change the way you assess the risk for this disease.”

A parasitic tapeworm called echinococcus multilocularis (E. multilocularis) can be fatal to humans.

A parasitic tapeworm called echinococcus multilocularis (E. multilocularis) can be fatal to humans.

Manigandan Lejeune Virapin

Recent studies of coyotes, foxes, and rodents in the province have found a high incidence of infected wild animals in areas across Alberta, including urban off-leash dog parks in Calgary. The infection is spread through the feces of coyotes and foxes that have eaten infected rodents. Dogs get the infection through contact with feces or eating infected rodents, then developing adult worms and passing eggs in their feces.

People can become infected by eating fruit or vegetables contaminated with parasitic eggs. The eggs aren’t visible to the human eye, so the infection can also happen from hand to mouth contact after handling contaminated soil or an infected pet’s fur.

“For pet owners, careful hygiene is important, as is regular veterinary care for their dogs,” says Massolo.

“Our data supports the hypothesis that the establishment of a European-like strain of E. multilocularis in animal hosts locally may result in the emergence of AE in North America,” Massolo says. “This strain has spread all over Alberta and it is very common. The fact that it is widely spread in wildlife, and the fact that it's the strain that is causing these human cases of AE really suggests very strongly that we are facing a new emergence. And a change in what we thought was the risk of AE. This would be the take-home message.”

Alessandro Massolo shared his research in a New England Journal of Medicine letter to the editor.

Alessandro Massolo shared his research in a New England Journal of Medicine letter to the editor.

Alessandro Massolo