Let’s Talk About Ticks!

Public Health 101

18 July 2022

Summer is here and many Ontarians will be spending time at cottages, getting away for staycations within the province, and generally spending more time outdoors. Unfortunately, summer is also the time when the risk of encountering a tick is at its highest.

Encountering a tick is as easy as brushing against bushes or long grass in a tick-infested area. Ticks are members of the arachnid family and are unable to jump or fly. They survive by attaching themselves to mammals and birds and feeding on their blood. Ticks thrive in wooded, brushy areas with undergrowth and significant leaf litter that keep the ground damp. Most ticks are about three to five millimetres in length, but can expand significantly in size after feeding.

Ticks in Ontario

Various species of ticks can be found in most parts of Ontario, clustering along the north shores of Lake Erie, Lake Ontario and the St. Lawrence River. It is possible, however, to find ticks anywhere in Ontario where they may have been transported by migratory birds. Although they are primarily active in spring and summer, ticks can be found any time of year when the temperature is above freezing.

There are a number of different tick species in Ontario, but Ixodes scapularis, the blacklegged tick (also known as the deer tick), is of particular concern from a public health perspective. Blacklegged ticks can carry the bacterium Borrelia burgdorferi which, if transmitted to humans via a tick bite, may cause Lyme disease.

Blacklegged Ticks and Lyme Disease

Lyme disease is a potentially serious infectious disease that can result from the bite of an infected blacklegged tick. In 2020, there were 5.7 confirmed cases of Lyme disease per 100,000 people in Ontario and cases have been rising for several years. Approximately 70% of all cases are reported in June, July and August. This peak in cases during the summer months coincides with both greater participation in outdoor activities and increased presence of ticks in the nymph stage of their lifecycle, when they are about the size of a poppy seed and very difficult to see.

Early symptoms of Lyme disease can include a ring-like rash that expands outward from the bite. Other symptoms may be flu-like, including fever, headache, muscle and joint pain, and fatigue. Find out more about Lyme disease and how to avoid exposure to infected ticks at the Ontario government's Lyme disease information page.

Blacklegged Tick Surveillance

Using tick surveillance data from Public Health Units (PHUs) across the province, Public Health Ontario (PHO) produces a Lyme Disease Estimated Risk Area Map each spring. The map highlights the Ontario regions where the risk of Lyme disease is higher due to the establishment of blacklegged tick populations. PHUs use the map as they investigate cases of Lyme disease. It can also help health care providers determine whether the location where a patient was bitten by a tick suggests a higher risk of Lyme disease.

In regions where there has been no history of blacklegged tick populations, blacklegged tick sightings and/or human cases of Lyme disease may indicate that active tick surveillance should take place. PHO has produced a number of resources to support PHUs with tick surveillance, including

PHUs outside of the established risk areas for Lyme disease can submit suspected blacklegged ticks to PHO for identification. Members of the public and health care providers can upload photos of ticks for identification to the eTick website or mobile app.

To learn more about Lyme disease and tick surveillance in Ontario, visit PHO’s Lyme disease page.

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Published 18 July 2022