Tick-borne bacteria increasingly widespread in Canada, study finds

Researchers from Quebec and Ontario are calling for better testing to track the spread of tick-borne germs as disease-causing bacteria gain new ground in Canada.

Ticks are blood-sucking arachnids that can carry pathogens – bacteria, viruses and parasites – like those that cause Lyme disease. Now, McGill University PhD candidate Kirsten Crandall says pathogens that are local to other regions are beginning to show up across central Canada.

“While the bacteria that causes Lyme disease is the most common tick-borne pathogen in Canada, other tick-borne pathogens are moving in,” she said in a media release published on Nov. 17.

In a study published in the medical journal Vector-Borne and Zoonotic Diseases on Nov. 9, Crandall and her co-authors from McGill and the University of Ottawa warned that two pathogens, Babesia odocoilei and Rickettsia rickettsii, had been detected in Canada outside of their historic geographic range.

Babesia odocoilei causes a malaria-like parasitic disease called babesiosis. Babesiosis can be asymptomatic or it can cause flu-like symptoms, such as fever, chills, sweats, headache, body aches, loss of appetite, nausea or fatigue.

Rickettsia rickettsii causes Rocky Mountain spotted fever, and is normally found in the United States, Western Canada, Mexico, Panama, Costa Rica, Argentina, Brazil, Colombia and Bolivia.

Both bacteria can infect animals and humans, and both were found in ticks and small mammals in Quebec. According to the study, climate change, habitat fragmentation and changes in the abundance of tick populations and their hosts are all driving the spread of emerging tick-borne pathogens like these across Canada.

“The presence of these pathogens changes the risk of disease for Canadians and animals in some densely populated areas of Canada,” Crandall said.

Crandall and her team made the detections using methods that went beyond those normally used in tick monitoring studies. By testing ticks at all life cycle stages, they discovered that female ticks can actually pass pathogens to their larval young. They also tested for pathogens not already listed as nationally notifiable diseases in Canada.

She said the findings demonstrate the need for better testing and tracking to detect the spread and potential risk of tick-borne pathogens to humans and animals throughout the country.

“Only two tick-borne pathogens are listed as nationally notifiable diseases in Canada: Lyme disease and tularemia," she said. "However, we are seeing increased cases of diseases like anaplasmosis and babesiosis in humans in Canada.”

Jeremy Kerr, a professor and research chair at the University of Ottawa's department of biology, said the study highlights the importance of funding more research into tick-borne diseases that haven't historically been common in Canada.

“If we don’t know that pathogens are present, we can’t equip Canadians with the information they need to protect themselves," he said in a statement released on Nov. 17. "COVID has diverted public health resources away from challenges like this one, and we need to remember that these tick-borne diseases are on the move too."