Tick-borne Illnesses in Canada - Part 2

Black-legged tickThis is the second of two posts looking at the tick-borne illnesses it's possible to contract in Canada. As you read though this post and the one I wrote in October keep in mind that our collective knowledge of tick-borne illnesses is far from complete. Some of the organisms that I describe in these posts have been known to exist for many decades and are well documented while many others are new to medicine and little is currently known about them. Still others have yet to be discovered.

The one thing that tick researchers know is that they don't know very much about what organisms live in and on ticks and how those organisms impact human health. Novel pathogens - infectious organisms previously unidentified in Canada or, in some cases, the world - are being discovered in this country on a fairly regular basis. And while it remains unknown what effect many of these organisms have on human health, there is growing concern that Canadians suffering from the types of symptoms that have become associated with chronic Lyme disease may not actually be contracting Lyme bacteria (Borrelia spp.) but other pathogens whose symptoms are masquerading as those caused by Lyme disease.

True Lyme disease is caused by infection with one of several closely related species of borrelia bacteria. In the past decade, quite a few unique species of borrelia bacteria have been identified in this country and many more are expected to discovered. Why? Because very little research has ever been done into tick-borne pathogens in Canada so the feeling is that the organisms that have been discovered so far are the tip of a very large iceberg.

I wrote about anaplasma, babesia, ehrlichia muris-like pathogen, Powassan virus, and relapsing tick fever in my previous post. Here are a few more tick-borne illnesses for you to wrap your head around:

Bartonella - Frequently listed as a Lyme disease co-infection, many in the scientific and medical communities remain skeptical that bartonella can be transmitted to humans by ticks. Those who believe it can, list the symptoms as including fever, fatigue, headache, poor appetite, swollen glands, neurological symptoms such as blurred vision, memory loss and balance problems, and a strange rash that looks an awful lot like stretch marks. The full range of symptoms remains unknown as do the number of people suffering from tick-borne bartonella infections both in Canada and abroad. The US Centers for Disease Control has firmly stated that there is no compelling evidence that ticks are transmitting bartonella to humans. However, researchers at the influential Lyme and Tick-Borne Diseases Research Center at the Columbia University Medical Center state that evidence for tick-borne transmission, although circumstantial, is "fairly strong". The fact remains that many Canadians have been diagnosed with bartonella, often by American doctors who specialize in tick-borne illnesses.

Borrelia miyamotoi - One of the relapsing fever borrelia, Borrelia miyamotoi (Bm) has been making headlines ever since it was discovered in Canada in 2011. Like Lyme disease, it causes flu-like symptoms including fevers, chills, headaches, body and joint pain and fatigue although the full range of symptoms remains unknown. Unlike Lyme disease, Bm rarely causes a rash and unlike the better known causative agent of relapsing tick fever, Borrelia hermsii (which I wrote about in my previous post) it is not detectable using existing tests for Lyme disease. Bm has been found in all provinces except Newfoundland and is thought to be widespread in nature. It's not currently known how many people have been infected with this bacterium in Canada.

Rocky Mountain Spotted Fever - Cased by a bacterium that is transmitted by the American dog tick, Rocky Mountain wood ticks and brown dog ticks, Rocky Mountain Spotted Fever (RMSF) can cause symptoms that include fever, headache, nausea, vomiting, red eyes, appetite loss, abdominal pain, muscle pain, light sensitivity, neck stiffness, and sometimes a distinctive scatter-shot rash. Although most people recover fully, some go on to experience long-term health effects. The number of cases in the US have increased significantly in the last 20 years. In Canada, the illness is restricted to the western provinces.

Tick paralysis - Caused by the bite of a breeding female tick, tick paralysis is the only tick-borne illness included in this series that is not caused by an infectious agent. Rather, it's caused by a powerful neurotoxin found in the salivary glands of female ticks that are about to lay eggs. It tends to affect girls under the age of 16 and men disproportionately, but it can affect anyone. American dog ticks, Rocky Mountain ticks, lone star ticks, black-legged ticks, and western black-legged ticks have been known to cause paralysis in humans. Symptoms include paralysis that starts in the feet and moves upwards, malaise, listlessness, and numbness or tingling in the face and limbs. Patients tend to make a rapid recovery once the tick has been removed. If the tick is not removed the paralysis can be life threatening. This illness occurs most commonly in western Canada.

Tularemia - While Borrelia miyamotoi has been snapping up all the headlines, tularemia is another illness that public health researchers have put forth as a possible explanation for Lyme-like symptoms in people who test negative for Lyme disease. Caused by a bacterium that has long been endemic to Canada, outbreaks of tularemia have been recorded in this country as far back as the 1940s. Symptoms can include sudden fevers, chills, headaches, diarrhea, aching muscles, swollen glands, eye inflammation, sore throats, tonsillitis, dry coughing, joint pain, chest pain, progressive weakness and trouble breathing. Although it can be transmitted by the bites of dog ticks, wood ticks and/or lone star ticks, it can also be acquired from a number of other sources, including biting flies, infected animals, under-cooked meat, dust, or contaminated water. It's considered rare, but the troubling rise in the number of people with Lyme-like symptoms has caused some to wonder if maybe it's a bit more common than previously thought.

With that, I'll conclude my trip through the tick-borne illnesses in this country. As more novel pathogens are found and more research is done into the health implications of these discoveries, it may be necessary to update this list at a later date.

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