Last fall, as the horrors of the Zika virus epidemic unfolded in South America, Canada considered itself lucky that the species of mosquitoes that transmit the virus don’t call this country home.
But experts on vector-borne diseases warn Canadians not to be complacent. Climate change is making Canada more hospitable to many new insects, some of which host bacteria that could pose serious challenges to our health system.
Lyme disease is already one such challenge. Virtually unknown in Canada a generation ago, the ticks that transmit the disease—Ixodes scapularis (the deer or black-legged tick) and Ixodes pacificus (the Western black-legged tick), native to the East and West coasts of the United States respectively, are now making themselves at home here. By 2020, an estimated 80 per cent of the population east of Saskatchewan will be living in tick territory.
As tick numbers have gone up, so too has the incidence of Lyme disease. The disease is difficult to quantify given uneven diagnostic and tracking practices. The Public Health Agency of Canada reported 522 cases in 2014, a fourfold increase over the 128 cases recorded in 2009, the year that Lyme disease became a reportable disease. And Steven Sternthal, the acting director general of the agency’s Centre for Food-borne, Environmental, and Zoonotic Infectious Diseases, cautions that this figure only reflects a fraction of all cases, estimating that Canada will be seeing well over 10,000 cases annually by 2020.
Calling Lyme a “serious emerging infectious disease,” Health Minister Jane Philpott is now overseeing the development of a “Federal Framework on Lyme Disease” that will set national guidelines on the prevention, identification, treatment, and management of the illness.
Most affected are the areas east of Saskatchewan plus British Columbia, because ticks prefer deciduous forests with ample leaf litter. But Patrick Leighton, an epidemiologist at the Université de Montréal specializing in tick biology and ecology, estimates that the line demarcating tick territory in Canada is shifting northwards by about 50 km a year. “Ticks are moving into new areas, and climate change is likely facilitating that change,” he says. “They need a long, warm summer to establish themselves in an area.” While ticks used to enter Canada on migratory birds and would survive for one season before being killed off by the long winter, global warming has enabled them to become endemic in many regions.
There is nothing endearing about the tick. A forest-dweller, it feeds off any warm-blooded animal within reach, typically deer, small rodents, and birds. Unlike the mosquito, which makes its presence known with an annoying buzz and itchy bite, the tiny deer tick often goes unnoticed. It burrows its head into flesh, secreting an immune suppressant that prevents its host from feeling the bite. Undisturbed, a tick will drink its fill of blood, typically for three or four days for a nymph or six or seven days for an adult, before falling off, sated. Researchers estimate that between five and 30 per cent of deer ticks carry Borrelia burgdorferi, the bacteria that cause Lyme disease, and, when present, the bacteria may transfer from tick to host.
One place in Canada where the deer tick has become endemic is Ontario’s Rondeau Provincial Park, a little tongue of land that sticks out into Lake Erie. Dawn Manning, who has summered in Rondeau for the past decade with her family, still loves the sand dunes, the vast beaches, and the historic little community of cottages, but she is wary of the tiny critter that has made itself at home there.
On the morning after Canada Day in 2014, Dawn was changing her two-year-old daughter’s diaper, when she found a tick embedded in Sarabeth’s thigh. They had spent the previous evening celebrating at a friend’s cottage nearby. The property next door, where Sarabeth had been ambling, was vacant and overgrown with the long grass that ticks often inhabit.
Dawn removed the tick with her fingernails, put it in a ziplock bag, and drove it and Sarabeth to the local health unit. The staff there identified it as a deer tick and sent it to the National Microbiology Laboratory in Winnipeg, Canada’s tick headquarters, to be tested for B. burgdorferi. Dawn’s family doctor said he would only prescribe antibiotics for Sarabeth if he knew for certain that the tick had been infected or if he saw sure signs of the disease taking hold.
“I’m so grateful that she developed a bull’s-eye rash,” says Dawn today, referring to one of the more definitive symptoms. The red concentric circles around the bite were enough to persuade Sarabeth’s doctor to prescribe the antibiotics that, if taken soon enough after being bitten, generally combat the infection.
Not all Lyme patients get the telltale rash, however (estimates are anywhere from nine to 70 per cent of all cases). Doctors should look for other indications of early acute infection, such as flu symptoms outside of flu season, especially when few people are coming into the doctor’s office with such symptoms. “We have to make clear to physicians that they should not expect to see the bull’s-eye rash,” says Jim Wilson, the president of the Canadian Lyme Disease Foundation, which has been involved in research and advocacy work on the disease since 2003. He mentions numbness, tingling, swollen joints, fatigue, brain fog, and confusion as classic symptoms.
But there’s no standard national protocol when it comes to tick bites. Generally, if the doctor can identify the tick as an Ixodes, and if Lyme is prevalent in the region, he or she will immediately prescribe an antibiotic, usually doxycycline. Otherwise, a provincial lab will determine if the tick carries B. burgdorferi; results could take four weeks. Lab tests on the patient’s blood are of limited use, as the antibodies they check for are rarely evident in the early stages of infection, and once they develop, can remain in the blood for a decade or more, making it virtually impossible to determine whether an infection is lingering or if, in fact, reinfection has occurred.
There is no one test that can be administered to patients that will check for all strains of the bacteria, and different strains are prevalent in different parts of the country. Over-the-counter kits that test the tick are not 100 per cent reliable and do not test for all strains. Moreover, a false negative could give you a false sense of security.
Diagnosis is further complicated by the variety of Lyme symptoms (different strains of B. burgdorferi manifest differently), which can mimic other illnesses. Most perplexingly, in roughly 20 per cent of all Lyme disease patients, symptoms persist long after antibiotic treatment has been completed. The term “chronic Lyme disease,” commonly used to describe this condition, is contested by most medical authorities, which prefer the term “post-treatment Lyme disease syndrome.” How best to treat these ongoing symptoms is a matter of debate.
The long-term prescription of antibiotics to treat Lyme disease is not recommended by the Association of Medical Microbiology and Infectious Disease Canada (AMMI Canada), to which the Canadian Medical Association defers on Lyme disease. New York State, on the other hand, has, since 2014, permitted long-term antibiotic treatment of Lyme and other tick-borne diseases. Maureen McShane, a family doctor in upstate New York who had Lyme disease in 2002, says that the vast majority of her roughly 2,000 patients come from Ontario and Quebec, many with cottages. These patients foot the bill themselves.
Daniel Gregson, an associate professor at the University of Calgary who specializes in infectious diseases, hopes that the new federal framework will find “the best strategies for identifying and treating patients” and a better understanding of the mechanism that causes these persistent symptoms, so that Canadians can access clinically proven treatment here rather than seeking “alternative forms of therapy” elsewhere. But, he cautions, “it’s just the beginning.”
As we go to press, Canada’s Public Health Agency is hearing from scientists, doctors, and patient groups at a national conference in Ottawa—input that will form the basis of the new framework. Gregson, representing AMMI Canada at the conference, expects a major focus on prevention, “the first motive in managing infections.” He’s also optimistic that a better test is in the works, as researchers work to identify blood markers other than antibodies that indicate infection.
Jim Wilson will also attend the conference. Wilson, who himself contracted Lyme in 1991 while living in Nova Scotia, and whose daughter got it a decade later in B.C., where the family now lives, hopes that the new framework will redress an imbalance. He feels many Lyme patients have not been well served by the system as it is. “We could and should have been doing a lot more,” he says, including more collaboration between patient advocacy groups, physicians, government, and medical associations. He also would like to see funding for human tissue study. “We need that data to make testing more accurate.”
Patrick Leighton, who spends a lot of time in tick-infested woods, stresses that “the risk is manageable.” He wears light-coloured clothing, tucks his pant legs into his socks, and, most importantly, conducts a thorough check at the end of the day, especially in the crevices, such as the armpit, the navel, and the crotch. Leighton points to Europe and Australia, where infection-bearing ticks abound but don’t prevent people from living healthy, balanced lives. “It shouldn’t keep people from enjoying the outdoors.”
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