By: Dr. Katie Clow DVM, PhD
      Post-Doctoral Fellow, Department of Pathobiology
      Ontario Veterinary College, University of Guelph, Guelph, ON, Canada

      May 31, 2018


With the warmer weather finally upon us, not only do we feel the need to be more active outside, but unfortunately so do the bugs! And included with those creepy crawly creatures are ticks.

There’s been a lot of talk about ticks over the last few years in many places of Canada. A big portion of this talk revolves around Lyme disease, which is a tick-borne disease that can affect people as well as our canine and equine companions.

 Let’s take a look at the top 5 things you should know about Lyme disease in dogs.


1. Dogs can only get Lyme disease from the bite of an infected blacklegged tick.

In northeastern North America, the blacklegged tick (Ixodes scapularis) is the tick species that can transmit Borrelia burgdorferi, the bacteria that causes Lyme disease. Blacklegged ticks can acquire the bacteria when they feed on white-footed mice or other small mammals harbouring B. burgdorferi. At their next blood meal, they can then transmit the bacteria to another ‘host’ (which could be a human, dog or horse). It takes about 24 hours for the bacteria to migrate out of the gut of the tick and then into the host, so quick removal of a tick can decrease the risk of transmission.

2. The risk of encountering a blacklegged tick varies by geographic area.

The blacklegged tick population has been expanding northward over the last few decades. In Ontario, the areas of highest risk are along the north shores of Lake Erie and Lake Ontario and most of eastern Ontario. This distribution continues to change, and Public Health Ontario routinely publishes a risk map to show you the areas where blacklegged ticks have been found (see: In general, this tick species prefers woodland habitat, so the likelihood of encountering this tick is much greater in forests and the surrounding brushy area.

3.  Most dogs that are exposed to the bacteria do not get sick.

Fortunately, exposure to the bacteria via the bite of an infected tick does not necessarily mean that your dog will get sick. It’s estimated that 95% of dogs that are exposed will not develop clinical signs. If a dog does get sick, the most common symptoms of Lyme disease are low energy, fever, lack of appetite and a ‘shifting lameness’ – which means a dog is limping on one leg one day, and then a different leg the next day. In very rare cases, Lyme disease can lead to a type of kidney failure.

4. Annual testing for Lyme disease is good practice.

Testing your dog is recommended on an annual basis. A simple in-clinic blood test can tell you if your dog has been exposed to B. burgdorferi but cannot tell you if your dog will get sick. There are several reasons this test is recommended, even if your dog is not showing any signs of disease. The most important reason is that it allows your veterinarian to conduct follow-up testing to ensure your dog stays healthy. For example, if your dog is positive, your veterinarian may request a urine sample to make sure there is no evidence of kidney disease. Additionally, testing allows your veterinarian to assess if your tick prevention strategies are working and if the risk of exposure within the area is changing.

5. Tick prevention is the best choice to keep your dog healthy.

Using a product that either repels ticks or kills ticks quickly once they bite is a great way to prevent the transmission of B. burgdorferi, and many other pathogens that can be transmitted to our canine companions by numerous species of ticks. Your veterinarian can help you find the best product that provides good protection against the ticks to which your dog may be exposed.

Conducting a thorough tick check on your dog (and yourself!) after a nice hike is still recommended, even if you use a tick preventative.

Vaccines also exist for Lyme disease. Although research is still needed in this area to fully understand the efficacy of these vaccines, in some scenarios they may be a useful addition to your dog’s preventative health care program (but not a replacement for tick prevention). Your veterinarian can help you decide if vaccination for Lyme disease is a good choice for your dog or not. 

If you’re looking for more information on ticks in Canada and the risks they may pose to your pet, a new website has just been launched:! This website is also home to the Pet Tick Tracker – here you can submit any tick you find on your pet and contribute to a growing database of pet tick surveillance.  

Bonus: Even though ticks pose a risk to our beloved companions, it is still important to get outside and enjoy the great outdoors with them. You just need to be aware of the risks and take the necessary precautions. For information on how to protect yourself, please visit the Public Health Agency of Canada’s website: or your local health unit.