Eastern Ontario is experiencing a surge in tick populations, prompting health officials to report the province’s highest levels of Lyme disease in 2025.
So far, Public Health Ontario has confirmed 186 cases in southeast and eastern Ontario—stretching from Prince Edward County to the Quebec border, including Ottawa—accounting for over half of Ontario’s total cases this year.
The South East Health Unit, which covers areas including Kingston, Brockville, Belleville, and Smiths Falls, has reported 132 cases, the highest rate in Ontario. Ottawa has recorded 41 cases, while the Eastern Ontario Health Unit has 13. Health officials say those numbers will likely rise due to delays in diagnosis and reporting.
The spike reflects a climate-driven expansion of blacklegged ticks, which carry the bacteria responsible for Lyme disease and anaplasmosis. Anaplasmosis, which causes flu-like symptoms and may require hospitalization, has seen 15 reported cases in Ontario so far this year.
To monitor the threat, Public Health Ontario now offers a real-time Ontario Vector-borne Disease Tool tracking tick- and mosquito-borne illnesses like Lyme, anaplasmosis, and West Nile virus. So far this year, only Lyme and anaplasmosis have been reported, though West Nile typically appears later in summer.
Ottawa Public Health urges people to take precautions outdoors: use insect repellents with DEET or icaridin, wear long sleeves and pants, tuck pants into socks, stick to trails, wear light-coloured clothing, and perform full-body tick checks after outdoor activities.
(Richard Evans)