Risk of Lyme Disease from Tick Bites in Thunder Bay or Ottawa
The risk of Lyme disease from tick bites is significantly higher in Ottawa compared to Thunder Bay, with Ottawa having an incidence rate of 18.1 cases per 100,000 population, making it a moderate-to-high risk area for Lyme disease transmission. 1
Geographic Risk Distribution
- Ottawa is located in eastern Ontario, which has experienced a marked increase in Lyme disease cases, with Ottawa specifically reporting an incidence rate of 18.1 cases per 100,000 population as of 2017 1
- Thunder Bay, located in northwestern Ontario, has a substantially lower risk as it falls outside the primary endemic regions identified in eastern Ontario 1
- The highest risk areas in Ontario are concentrated in the eastern part of the province, particularly in Leeds-Grenville and Lanark District (128.8 cases per 100,000), Kingston-Frontenac, Lennox and Addington (87.2 cases per 100,000), and Hastings and Prince Edward Counties (28.6 cases per 100,000) 1
Risk Factors for Lyme Disease Transmission
- Lyme disease risk is determined by three key factors:
- Density of vector ticks (Ixodes scapularis) in the environment
- Prevalence of Borrelia burgdorferi infection in these ticks
- Extent of person-tick contact through outdoor activities 2
- Approximately 15%-30% of Ixodes scapularis nymphs in highly endemic areas carry the Borrelia burgdorferi bacteria 2
- Transmission of Borrelia burgdorferi typically requires a minimum of 36 hours of tick attachment 3, 2
Seasonal Risk Variation
- Lyme disease cases occur predominantly from June through September, coinciding with the nymphal tick feeding season 1
- Nymphal ticks, which are most active in late spring and early summer, are responsible for the majority of Lyme disease cases 2
- Risk is highest when engaging in outdoor activities during these peak months 2
Population Risk Factors
- Males and individuals aged 5-14 and 50-69 years have the highest reported rates of Lyme disease in Ontario 1
- People who live in less urbanized areas with higher socioeconomic status have increased odds of Lyme disease infection 4
- Individuals living in neighborhoods with high probability of tick occurrence have 2.2 times higher odds of contracting Lyme disease 4
Risk Reduction Strategies
- Personal protective measures are highly effective when consistently applied:
- Environmental modifications can reduce tick populations:
- Remove leaf litter and brush around homes
- Clear trees and brush to reduce tick habitat
- Create barriers between wooded areas and lawns 2
- Prompt removal of attached ticks within 24 hours significantly reduces transmission risk 3
Post-Exposure Management
- Single-dose doxycycline (200 mg) can be used as prophylaxis within 72 hours of tick removal if:
- The tick is identified as Ixodes scapularis
- The tick was attached for ≥36 hours
- The bite occurred in a highly endemic area (such as Ottawa)
- Doxycycline is not contraindicated 5
- Monitor for signs of infection for 30 days after a tick bite, including the characteristic erythema migrans rash, fever, malaise, fatigue, headache, muscle and joint pain 5, 6
Important Considerations
- Climate change is contributing to the expansion of blacklegged tick habitats in Ontario, which will likely increase Lyme disease risk in more regions over time 1, 7
- Laboratory testing for Lyme disease should be guided by specific suspected tick-borne pathogens based on geographic location, tick species, and clinical presentation rather than routine testing 8
- Early diagnosis and treatment significantly reduce the risk of complications from Lyme disease 2