Lyme disease is caused by a bite from a tick infected with the bacterium Borrelia burgdorferi. In Québec, blacklegged ticks, also called deer ticks, can transmit the disease.

Populations of this species of tick are established in the south of the province. The risk of infection is increasing, both in animals and humans.           

For more details on the risk of infection in humans, visit the Lyme disease page in the Health section.

At-risk animals

Lyme disease primarily affects dogs, horses, donkeys and mules.

Signs of the disease in animals

Ticks are very small mites. Their bites can easily go unnoticed.

Infected animals generally do not show any symptoms. If there are signs of the disease, they vary in severity and present differently depending on the species.

Generally, kidney damage (nephritis) and lameness caused by joint pain that alternates between each leg is observed. Sometimes, a fever, fatigue, appetite loss, a lack of energy and swollen lymph nodes may occur.

A skin rash can expand around the site of the tick bite. It’s rarely visible under an animal’s fur.

In dogs

Only 5% to 10% of infected dogs show signs of the disease, which develop two to five months after the dog is bitten by an infected tick.

These signs generally disappear on their own in less than a week. Sometimes, they reappear cyclically. If the disease is not treated quickly, it can cause heart, neurological or kidney problems that are often fatal.

In horses, donkeys and mules

In addition to generally observed signs, changes in behaviour and other neurological signs may occur. Some horses develop eye problems.

Transmission and incubation period

In Québec, only a bite from an infected blacklegged tick can transmit Lyme disease. The risk is low if the tick is attached to the skin for less than 24 hours. If the tick is attached for longer than that, the risk increases.

Ticks do not jump or fly. Generally, they wait in leaf litter on the ground, in tall grasses or in bushes until an animal or human goes by.

Before a tick feeds, it can vary in size between 1 and 3 millimetres. It can triple in size when filled with blood. It needs to feed on animal or human blood at each stage of development, from larva to nymph to adult.

The disease does not spread from an infected animal to humans or by contact between people. If a blacklegged tick is found on an animal, that can indicate that there are other ticks in the immediate environment or in an area where the animal was found recently. Pet and other animal owners would therefore be at risk of coming into contact with ticks that transmit the disease.


If your animal shows signs of the disease, contact a veterinarian. A consultation will determine if antibiotics are required.

Protection and prevention

Blacklegged ticks capable of transmitting Lyme disease can be active at temperatures of 4°C or higher. They reach their optimal level of activity at around 25°C.

The risk of being bitten is highest in spring and summer, but it continues into the fall. During tick season, it’s important to take steps to protect yourself and your animals.

Several measures can help prevent this disease in animals and humans.

Avoiding tick bites

The best way to prevent the disease is to avoid tick bites.

If your animal has easy access to a forest, wooded areas or tall grasses, your veterinarian can provide advice about products to protect your animals.

Reducing the number of ticks

Other methods help reduce the number of ticks in your immediate environment.

Regularly maintain your property and buildings to limit the number of rodents, which often carry the bacterium and cause immature ticks to become infected.

Manage the vegetation around the periphery of your home and in play areas. Keep your grass cut, and clear away any leaf litter that accumulates on the ground.

Installing a fence to keep white-tailed deer at a distance is recommended. Adult blacklegged ticks prefer these deer, as they provide an appropriate environment for ticks to mature and reproduce.

What to do if you find a tick

Within two hours of returning from an outdoor activity, use a brush to check if there are any ticks on your animal. If you find a tick, remove it using a pair of tweezers that will not crush the abdomen (such as fine-tipped tweezers).

If the head of the tick remains implanted in the skin, you can then gently remove it with the tweezers. If you are unable to remove it, leave the head of the tick in place and wait for the skin to heal, because the head cannot transmit Lyme disease. For more details, visit the page Removing a tick after a bite.

Keep the tick refrigerated at 4°C in a tightly closed container. Take note of the location of the bite and the date and the places where the animal may have gone. The tick and that information will be used if you need to consult a doctor or veterinarian.


The surveillance system has made it possible to identify several regions in the south of the province where the risk of transmission of the disease is greater. It has been observed that the proportion of infected ticks varies and is generally low, rarely exceeding 20%.

It is mandatory to report human cases of Lyme disease. Ticks found on humans, on animals (in certain regions of Québec) and in the environment are used to determine their increased presence in zones where they are established as well as the percentage of ticks carrying the bacteria that causes the disease. That’s how we can better assess the risks for Quebecers.

Visit the Lyme disease page to find out more about the situation in Québec.

Hospitals and medical and vet clinics send ticks to the Laboratoire de santé publique du Québec. The lab identifies the tick species and sends blacklegged ticks to the National Microbiology Laboratory in Winnipeg. For more information, visit the Diseases transmitted by ticks This hyperlink will open in a new window. page on the website of the Laboratoire de santé publique du Québec.

Analysis of ticks found on animals is conducted in the following regions: Bas-Saint-Laurent, Saguenay–Lac-Saint-Jean, Abitibi-Témiscamingue, Côte-Nord, Nord-du-Québec and Gaspésie–Îles-de-la-Madeleine. That makes it possible to monitor the extent of ticks in these regions.

Last update: July 18, 2023


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