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Summer is on the way, and with it, the growing problem of Lyme disease. The Public Health Agency of Canada says cases are on the rise, and a new study published this month maps out the risk.
The study looked at 1,230 cases of Lyme disease reported in Ontario from 2005 to 2014. During that time, the incidence went up six-fold.
In 70 per cent of the cases, patients had erythema migrans or EM, the typical flat to slightly raised erythematous or red-coloured rash that appears at the site of the tick bite seven to 10 days on average following the bite.
Seventy-five per cent of the patients had flu-like symptoms, 42 per cent had arthritis, 41 per cent had neurological symptoms and six per cent had heart symptoms.
One-third of the patients had early localized disease consisting of a rash with flu-like symptoms. Just over 200 had early disseminated Lyme disease causing the rash plus mostly neurological symptoms. More than a third had late disseminated disease presenting as skin rash, neurological symptoms and arthritis.
There are several reasons why cases of Lyme disease are on the rise. Better detection is one reason why more cases are being diagnosed. Scientists at the B.C. Centre for Disease Control concluded that it’s mostly due to a new more sensitive test for Lyme disease.
They added that for every case of Lyme disease reported to authorities, eight to 10 other cases go unreported. However, authorities don’t rule out the possibility that more Canadians have been contracting the disease.
Climate change is likely playing a role in the growing incidence of Lyme disease in Canada and in the northeastern part of the U.S. Humans get infected by a bite from an infected black-legged tick or nymph.
Black-legged ticks used to be called deer ticks because it scientists once believe that they could only be found in areas where deer roam. However, the ticks are increasingly being found in areas not known for having deer, hence the name change.*
Climate change means that the typical hosts of black-legged ticks such as the white-tailed deer and white-footed mice are able to migrate into Canada.
In the past, adult ticks lived in season, but earlier springs and longer fall seasons permit them to live close to year-round.
Spring and summer are times when humans are outdoors. So are tick nymphs, which are most active from May to August. Unlike adult ticks, nymphs are as tiny as a poppy seed, and just as difficult to notice, which makes them a frequent vector for Lyme in humans.
Diagnosing Lyme disease
My sense is that doctors are hit-and-miss in diagnosing Lyme. If you present to a doctor with early localized Lyme disease and a characteristic rash, there’s a good chance you’ll get a correct diagnosis and appropriate treatment. The longer the disease has gone on and the more disseminated it becomes, the less helpful some doctors become.
Then, there’s the matter of the tick bite. Some doctors believe (erroneously) that you can’t get Lyme disease if you haven’t had an obvious bite. The fact that Lyme disease can be transmitted by nymphs puts paid to that assumption. The U.S. Centers for Disease Control says most humans are infected through the bites of nymphs that are less than two millimetres and difficult to see.
Then there’s the controversy surrounding so-called chronic Lyme disease. Many patients complain of ongoing symptoms of chronic infection. Often, they have joint and muscle pain, dizziness, vertigo, fatigue, headaches and chest pain.
They get tested for multiple sclerosis, lupus, chronic fatigue and fibromyalgia, and all of them are ruled out. A 2014 review in the journal Clinical Infectious Diseases did not support the idea of chronic Lyme infection, and the CDC discourages use of the term. Many people who have had a tough time getting diagnosed disagree strenuously with that.
The Mayo Clinic Health Letter has a good article on Lyme disease. The best way to prevent it is to avoid wooded, bushy areas with long grass.
If you can’t, then wear shoes with long pants tucked into your socks, a long-sleeved shirt, a hat and gloves. Stay on trails and avoid walking through low bushes and long grass. Apply DEET insect repellent 20 per cent or higher concentration to your skin. Apply products with permethrin to clothing or buy pretreated clothing.
Check yourself carefully for ticks that may be no bigger than the head of a pin. Shower as soon as you come indoors. Ticks often remain on your skin for hours before attaching themselves. Showering and using a washcloth might remove unattached ticks.
Patients who think they have Lyme disease should see their health professional for a preliminary ELISA antibody test and, if positive, a western blot test.
Early-stage Lyme disease is treated with a 14 to 21 days course of oral antibiotics. Intravenous antibiotics for up to 28 days may be recommended if the disease involves the central nervous system.
Lyme disease is on the rise in Canada. Doctors and patients need to prepare for it.
Dr. Brian Goldman is an ER physician in Toronto. His new book, The Power of Kindness: Why Empathy is Essential in Everyday Life, is published by HarperCollins.
* The blog contains updated information.
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