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.

This species of tick is established in the south of the province. Québec’s populations of bacteria-carrying ticks are growing, and with them the risk of infection for both animals and humans.

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

At-risk animals

Among domestic animals, Lyme disease primarily affects dogs, horses, donkeys and mules.

The wild animals that primarily act as reservoirs for the bacterium that causes Lyme disease are rodents such as white-footed mice. A tick in one of its early stages of development (larva or nymph) can get infected by biting a rodent or bird, as birds can also be reservoirs. Ticks in their final stage of development (adult) are often abundant on white-tailed deer. However, deer are not carriers of the bacterium and do not transmit it to ticks when bitten.

Contrary to popular belief, the North American opossum does not play any part in controlling or preventing the spread of Lyme disease This hyperlink will open in a new window. (French only), even if it eats ticks found in its fur while grooming. Opossums, like other small mammals, can be infected by the bacterium that causes Lyme disease.

Signs of the disease in animals

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

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

Kidney damage (nephritis) and lameness caused by joint pain that alternates between each leg is observed in some domestic animals. 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.

The disease does not spread from an infected animal to humans or by contact between people. If a blacklegged tick is found on a domestic 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 domestic 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 for protection.

Reducing the number of ticks

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

For example, it’s recommended that you 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.

Regular maintenance of your property and buildings will limit the number of rodents, which often carry ticks and the bacterium.

Installing a fence to keep white-tailed deer at a distance is also recommended. 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, 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.


Lyme disease surveillance 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 domestic animals (in certain regions of Québec) and in the environment are used to monitor the zones where they are established as well as the percentage of ticks carrying the bacterium that causes the disease, so that 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.

Ticks found on domestic animals and collected by veterinarians are analyzed when they come from 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 spread of ticks in these regions.

Last update: March 5, 2024


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