Tick-borne Disease Information for Health Care Professionals

As per provincial standards, there are risk areas where black-legged ticks are known to have established endemic populations within northwestern Ontario. The black-legged tick is the primary vector of the four tick-borne diseases listed as Diseases of Public Health Significance (DoPHS):

anaplasmosis
babesiosis
Lyme disease
Powassan virus infection.

Please see Public Health Ontario’s 2024 Ontario Blacklegged Tick Established Risk Areas Map to understand where black-legged ticks are present (previously the Ontario Lyme Disease Map: estimated risk areas).

Estimated Risk Area data is more robust in areas where human populations and suitable habitats for black-legged ticks overlap. It is possible to encounter an infected black-legged tick anywhere in the province where ticks can live.

Active tick surveillance (tick dragging)

NWHU conducts active tick surveillance (tick-dragging) twice per year, in the spring and fall, to track the migration of tick populations throughout our region and identify tick-borne diseases they are carrying.

Active tick surveillance results

As part of our 2023 fall active tick surveillance, Powassan virus was detected in a small number of black-legged ticks collected in the Fort Frances area, and we issued a Public Health Alert. It is uncertain whether black-legged ticks will continue to test positive for Powassan virus; however, we will continue active tick surveillance to determine if this is an ongoing risk for the area. The bacteria that cause anaplasmosis and babesiosis have been identified as part of our active tick surveillance over the past 10 years, which indicates their transmission cycles are supported. Anaplasmosis and babesiosis will likely persist among tick populations in our region.

Lyme disease

Symptoms, testing, diagnosis, and treatment

See the following for Lyme disease-specific information:

Surveillance statistics from 2023’s active tick dragging show that more than 20% of black-legged ticks in our area are positive for Borrelia burgdorferi (the bacteria that can cause Lyme disease.)

Lyme disease post-exposure prophylaxis criteria are the same as before:

Blacklegged tick attached for more than 24 hours AND
Tick acquired in a risk area with more than 20% infected ticks (this includes the risk areas of NWHU) AND
It has been less than 72 hours since the tick was removed AND
There are no contraindications for doxycycline.

Pharmacists can reference Assessment and Prescribing Algorithm for Pharmacists: Antibiotic Prophylaxis to Prevent Lyme Disease following a Tick Bite.

As part of our infectious disease surveillance for 2023, there were zero (0) confirmed cases of Lyme disease infection reported in the NWHU area. In 2022, there were seven (7) confirmed cases of Lyme disease reported, an incidence rate of 8.6 cases per 100,000. Due to relatively small numbers, Lyme disease incidence fluctuates year to year in the area, with a general increasing trend consistent with provincial trends in recent years. Provincially in 2023, there were 1799 confirmed cases of Lyme disease reported, an incidence rate of 11.7 cases per 100,000¹.

Please note that only patients tested and lab-confirmed with Lyme disease infection will be captured in this data. Post-exposure prophylaxis (PEP) prevents the progression to Lyme disease. The number of human Lyme disease cases should not be used to interpret disease endemicity or risk at a population level but may indicate a need for increased awareness and use of PEP in a particular cohort or geographical area.

Other tick-borne diseases

Symptoms, testing, diagnosis, and treatment

See the following for information related to other tick-borne diseases:

As part of our infectious disease surveillance for 2023, there was one (1) confirmed case of anaplasmosis reported in the NWHU region, an incidence rate of 1.2 cases per 100,00, and zero (0) confirmed cases of babesiosis and Powassan virus infection reported. Provincially in 2023, there were seventeen (17) confirmed cases of anaplasmosis (0.1 per 100,000), eight (8) confirmed cases of babesiosis (0.1 per 100,000) and zero (0) confirmed cases of Powassan virus infection reported².

Please see Enhanced Epidemiological Summary: Anaplasmosis and Babesiosis in Ontario: 2023

Reporting tick-borne diseases

Anaplasmosis, babesiosis, Lyme disease and Powassan virus infection are reportable Diseases of Public Health Significance (DoPHS), under the Health Protection and Promotion Act. Reporting allows for routine, ongoing surveillance, and the identification of endemic areas.

To report a tick-borne disease, visit our Reporting Diseases of Public Health Significance page.

Tick-borne disease webinars for health care providers