Lyme disease cases rising in Canada; climate change cited as a probable factor

More Canadians are contracting Lyme disease and federal health officials are partly blaming global warming for a dramatic uptick in cases.

Lyme disease is caused by the bacterium Borrelia burgdorferi, which is transmitted to people by black-legged ticks that get infected after biting mice or deer that carry the bug. These ticks are referred to as vectors for the disease.

"As climates change across the country, that is certainly one of the major factors why we believe that it has spread in recent years," Health Minister Jane Philpott told reporters after addressing a national conference on Lyme disease in Ottawa on Monday.

"The vectors have spread and we expect it to continue to change and it needs to be monitored closely," Philpott added.

In 2015, there were 700 new cases of Lyme disease reported to the Public Health Agency of Canada (PHAC), up from 140 cases in 2009. Lyme is now being diagnosed in southern B.C., Manitoba, Ontario, Quebec, Nova Scotia and New Brunswick.

But PHAC chief Dr. Gregory Taylor said those figures are likely under-reported.

"We have estimates it could be thousands of Canadians getting infected, not just several hundred, and that is worrisome," Taylor said in an interview from Ottawa.

Some estimates project that Canada could see from 10,000 to 20,000 a cases a year if the ticks that carry the bacterium continue to expand their range into other parts of Canada.

In North America, the disease was first identified as a tick-borne infection in 1978 in the town of Lyme, Conn., and has been endemic in Canada since the early 1980s.

Immediate symptoms of Lyme disease include fever, headache, body pain, fatigue and in some cases a bull's-eye rash at the site of the bite. Treatment with a short-term course of antibiotics can cure the illness.

But not all of those infected get that tell-tale rash, making it difficult for some patients to get early diagnosis and timely treatment, said Taylor, explaining that many doctors are unfamiliar with the hallmarks of the illness, having never seen a case.

"And part of what people worry about is that some clinicians think that you must have that rash to have Lyme, which is just not true. We know that not all patients have the bull's-eye rash. They can have a rash that doesn't look like a bull's eye or they can have no rash whatsoever."

If not treated promptly or left untreated altogether, Lyme can develop into a "very debilitating" chronic condition marked by lingering muscle and joint pain and neurological disturbances that can last many months.

Without a diagnosis based on symptoms, doctors can turn to tests that look for antibodies to the bacterium in a blood sample. But these tests are notorious for false-positive and false-negative results.

Some patients who have been told they don't have Lyme — but nevertheless believe they are infected with the tick-borne bacterium — seek tests at U.S. clinics and get "a diagnosis of Lyme disease, which they would not get in Canada," said Taylor, noting that Canadian labs follow the same test-interpreting guidelines used in Europe and by the U.S. Centers for Disease Control.

That can lead some doctors to prescribe months-long antibiotic treatment, which Taylor said can cause adverse side-effects as well as contributing to drug-resistance by various bacteria, which one day could include B. burgdorferi.

Still, he conceded that current blood screens for antibodies are difficult to interpret "at the best of times.... Everyone agrees that we have to have better laboratory testing."

The three-day conference has brought together patient groups, researchers and policy experts with the aim of creating a national framework for tackling Lyme disease, including developing better tracking of human cases and the spread of ticks; treatment guidelines; and educating health providers and the public about the disease.

Jim Wilson, president of the Canadian Lyme Disease Foundation, told attendees the conference is only a starting point.

Patients and the clinical experts who support them must be treated as equal partners in decision-making about guidelines for diagnosing, treating and preventing Lyme, as well as in choosing how best to track its spread and what research into the disease should be funded, he said.

"We need to truly identify the burden of Lyme borreliosis currently in our chronically ill population, and to find better ways to identify future victims of the disease," said Wilson, whose non-profit organization is dedicated to promoting better diagnosis and treatment of Lyme disease, as well as research and education.

"And here we are in 2016 and Canada has no idea how many Canadians now or over the previous decades contracted Lyme disease because the protocols in place for testing and clinical diagnostics have had big gaping holes and still do."

With files from Kristy Kirkup

The Canadian Press