Article courtesy of The Toronto Star: https://www.thestar.com/life/health_wellness/2017/07/17/doctors-notes-dont-let-fear-of-lyme-disease-keep-you-inside.html
This summer is shaping up to be a very big tick season because the weather has been cool and wet — ideal conditions for the black-legged tick that carries the bacteria causing Lyme disease. If this sounds worrisome, I’ve got good and bad news.
First, a reality check. Estimates from early Lyme disease vaccine trials suggest that about 90 per cent of people infected with the bacteria don’t develop major symptoms of the disease such as arthritis. Many don’t know they’re infected. Ten per cent are diagnosed with Lyme disease and receive antibiotics, and of those, another 10 per cent have a version of Lyme that doesn’t respond well to treatment. This means about one per cent of people infected with Lyme bacteria suffer the terrible, often crippling, long-lasting symptoms that make this disease so feared — but 99 per cent don’t.
Lyme disease isn’t common yet in many parts of Ontario, including the Toronto region, because traditionally our climate doesn’t allow ticks to survive the winter in large numbers. Ticks are collected from Ontario parks and other areas with woods and tall grasses and tested for the presence of the bacteria that cause Lyme disease. So far the numbers of these arthropods carrying Lyme disease bacteria has been relatively small compared to regions in the U.S. where Lyme disease is an important public health problem. This suggests the risk is low — for now.
However, this risk is growing rapidly. By 2020, all of southern Ontario extending east to Quebec and north to southern parts of Algonquin Park will be high-risk areas for Lyme-carrying ticks, and regions extending up to Wawa will be moderate risk areas.
Because our climate is warming, the GTA has developed the ideal conditions for ticks to live here year-round. This has already started in sites on the north shore of Lake Erie such as Point Pelee. Traditionally, our ticks come from birds flying up from the U.S. each spring. But instead of dying when cold weather hits, our ticks will live on, feeding off small rodents like chipmunks, squirrels and mice, which in turn pass the bacteria onto other ticks. Once established, the bacteria causing Lyme appears impossible to eradicate. Spraying has proven ineffective, and there’s no way to destroy every living mammal a tick can feed on.
As well, we don’t yet understand why some people develop long-lasting illness from Lyme that is not resolved by antibiotic treatment. We do know that these people appear to have genes making them more susceptible to autoimmune diseases like rheumatoid arthritis. Many researchers are trying to understand more about this so that new treatments can be developed, and so that we can predict who is at risk for the severe version of the disease. But this work is slow by nature.
That’s why I believe prevention is our best bet. Rather than avoiding the great outdoors, we need to get into the habit of showering after a day in nature to wash off ticks that haven’t latched on yet (typically, ticks make their way slowly to warm, protected areas like the groin, armpits or under breasts). Tick checks are very helpful, especially since a tick needs to feed for 36 to 48 hours before transmitting the bacteria.
I’m also encouraged by news that a potential new Lyme vaccine is entering early clinical trials in Europe and the U.S. It’s possible that this vaccine will be ready for use in a few years — right about when we’re predicted to see a big buildup of the Lyme bacteria in our ticks and animals.
Another reason to focus on prevention: current well-validated tests to diagnose Lyme aren’t sufficiently sensitive in the early stage of the disease. Although many researchers are trying to develop better ones, there’s nothing with substantial promise around the corner. It’s a tricky disease — we think it’s hard to detect because there are many strains of Lyme, and because something may be preventing development of the antibodies that reveal the disease.
Unfortunately, Lyme disease is going to be a part of life in Ontario in the coming years, so it would be a shame to let fear get in the way of enjoying the outdoors. As a Lyme researcher, I’m well aware that infected ticks are found in Scarborough’s Rouge Valley, but I still hike there regularly. My dogs have a canine tick vaccine, and I shower after a hike, and check myself for ticks.
As Lyme spreads into Ontario, at least we aren’t being caught by surprise. We’ve learned much about how to protect ourselves since 1975, when the first cluster was identified in Old Lyme, Connecticut. And a great many scientists, myself included, are dedicated to understanding Lyme and developing better treatments.
Tara Moriarty is an assistant professor in the Department of Laboratory Medicine and Pathobiology. Doctors’ Notes is a weekly column by members of the U of T Faculty of Medicine. Email email@example.com
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