Canadian scientists track Lyme disease threat

Health officials combine surveillance of human cases, dogs and ticks in the field to track the spread of the disease across the country.

Dog owners can help stop the spread of the disease by reporting ticks they find on their pets

Veterinarian Scott Weese with his dog Merlin. Weese has dog owners identify ticks from their pets as part of an early warning system for disease risk in humans. (Craig Chivers/CBC)

An increase in cases of Lyme disease in Canada could be the result of greater awareness and better testing, say experts who remind those heading out in risky areas to take precautions.

In 2009, the Public Health Agency of Canada recorded 144 cases of Lyme disease in the country. In 2016, there were 992 cases countrywide. The illness is caused by a type of bacteria transmitted to humans through the bite of an infected tick, such as the blacklegged tick and western blacklegged tick.

Ticks pick up the bacteria from feeding on rodents, birds and other small animals. Large animals, such as deer, are also needed for the bacteria to complete their life cycle. 

Pets can help track ticks

For a tick to be able to pass on the infection to a human, it has to be the right type of tick and it has to carry the bacteria, said Scott Weese, a veterinarian and professor at the University of Guelph.

Weese co-ordinates the Pet Tick Tracker, a site that asks pet owners and vets to help monitor and track the spread of ticks in Canada by helping them to identify pests collected from dogs.

"They're probably in many ways better sentinels, because they're low to the ground, they root around, they go in some areas off paths that we don't go. So they're going into those tick areas more intensively than we are," Weese said.

Pet dogs are routinely tested for Lyme disease with records going back decades. Weese said the dog data can provide an early warning system to link exposures in canines to what's going on in people.

Lyme disease surveillance in Canada is also based on reports of human Lyme disease, which is nationally notifiable. As well, scientists conduct active tick surveillance — collecting ticks from the environment by dragging flannel sheets through the tall grass.

An adult female blacklegged tick is shown with a quarter for scale. People should check for adult and juvenile ticks on their body when returning from the woods, health officials advise. (CBC)

In Canada, people are at risk for contracting Lyme disease based on where they live or travel or whether they visit wooded areas with tall grass, rushes or moist environments. 

Dr. Nick Ogden, a veterinarian, studies tick ecology with the Public Health Agency of Canada in Saint-Bruno, Que.

"I'm concerned about it. It has gone from something we raised as a hypothesis about 10 to 12 years ago that there might be emerging Lyme disease … to a reality," said Ogden.

Spreading risk

Ticks are becoming more common from the Maritimes through Quebec, Ontario and into southern Manitoba, Ogden said. Local and provincial public health units have more specific maps of their prevalence. 

Ogden called Lyme disease an emerging public health issue. He said Canadians should know three things about it:

  • How to prevent infection by wearing long trousers and long-sleeved shirts and insect repellent containing DEET or icaridin on clothes and exposed skin.
  • Check for ticks when returning from the woods and remove any within 24 to 36 hours to reduce the risk. Put clothes in the dryer on a hot setting to kill any acquired ticks. 
  • Know symptoms of a tick bite and consult a health-care professional if you experience any.

"I think we can manage the risk," Ogden said.

People should be aware but not concerned, Weese suggested. "Keeping a perspective is the key, right? I'm much better off being outside with my dog, getting lots of exercise, rather than staying in my office all day in front of a screen."

Vaccine in the works

For their part, scientists are conducting more lab tests, said Muhammad Morshed with the BC Centre for Disease Control public health lab.

"Last year we tested over 6,000 samples," Morshed said, up from about 500 tests a year about two decades ago.

The risk is still relatively low and experts say the threat of Lyme disease shouldn't keep you from going outdoors — but they do have tips on how to avoid ticks. 3:00

Morshed said there are still many questions, but research is advancing, including on a vaccine.

"It's still not there, but there is an animal vaccine available," Morshed said. "For a human vaccine, people are desperately working on it so we might be able to get good news in about three to five years."

A previous Lyme disease vaccine is no longer available as the manufacturer discontinued production, the U.S. Centers for Disease Control and Prevention's website says. 

Sources: Public Health Agency of Canada, U.S. Centers for Disease Control and Prevention, Health Canada and Canadian Lyme Disease Foundation (CBC)

With files from CBC's Amina Zafar and Christine Birak