Blacklegged Tick “Hot Spots” Emerging in Northern Canada

Blacklegged ticks are appearing in unexpected regions of Canada, creating new “hot spots” of Lyme disease risk—even in areas previously considered unsuitable.

This shift highlights the evolving geographic footprint of tick-borne disease.

Unexpected Tick Hot Spots Identified

Ticks were collected through a surveillance program involving veterinary clinics and the public between 2014 and 2016.

Investigators identified clusters of Ixodes scapularis ticks in northern New Brunswick, including areas not typically thought to support tick populations.

These findings suggest that Lyme disease risk is expanding beyond traditional environmental limits.

Dogs Reveal Hidden Risk

Most infected dogs were located in south-central regions, but seropositive dogs were also identified in northern pockets.

These canine “hot spots” likely reflect increased risk for humans in the same areas.

How Are Ticks Reaching These Areas?

The most likely explanation is long-distance transport by migratory birds.

Ticks can attach to birds and be carried far beyond their typical habitat, allowing them to “leapfrog” into new regions.

This mechanism enables tick populations to establish in areas previously considered too cold or unsuitable.

Citizen Science Reveals More Than Expected

Tick detection rates were significantly higher when members of the public participated in surveillance compared to traditional professional methods.

This suggests that tick prevalence in northern regions may be underestimated.

Why This Matters

As ticks expand into new geographic areas, clinicians and the public may not recognize the risk.

This can lead to delayed diagnosis when Lyme disease is not considered in regions previously thought to be low-risk.

Clinical Takeaway

Lyme disease risk is expanding into northern Canada. Clinicians should consider Lyme disease even in regions where ticks were historically uncommon, particularly when patients present with compatible symptoms.

Related Articles:

Dogs in Canada at risk for Lyme disease

Back yards at risk of migrating deer ticks

Tracking ticks in Canada with digital images

Hundreds of infected ticks found in one yard in Canada

References:

Lieske DJ, Lloyd VK. Predicting the distribution of Ixodes scapularis in Canada. Ticks Tick Borne Dis. 2018.
Lewis J, et al. Citizen science in tick surveillance. Healthcare (Basel). 2018.

Dr. Daniel Cameron, MD, MPH
Lyme disease clinician with over 30 years of experience and past president of ILADS.

Symptoms • Testing • Coinfections • Recovery • Pediatric • Prevention