Surveillance for Ixodes scapularis and Ixodes pacificus ticks and their associated pathogens in Canada, 2021

Ixodes scapularis and Ixodes pacificus ticks pose risk of infection with tick-borne diseases in Eastern and Pacific Western Canada, respectively.

In 2021, passive and active tick surveillance programs collected ticks and associated data elements, including location, infection and other characteristics, to monitor their populations and inform public health prevention and mitigation activities.

Surveillance data for ticks were compiled from the National Microbiology Laboratory (Public Health Agency of Canada), provincial public health, Canadian Lyme Disease Research Network and eTick (an image-based online platform). A descriptive analysis of tick records and infection prevalence of tick-borne pathogens is presented. Seasonal trends are described.

During 2021, 6,892 I. scapularis ticks were identified across all ten provinces via passive surveillance with 777 I. pacificus ticks collected from British Columbia. Most were adult female ticks, collected from human hosts in the spring (March-May) or fall (October-November) seasons. The most common pathogen, Borrelia burgdorferi, was detected in 18.6% (95% CI: 17.2%-20.1%) of samples. Active surveillance resulted in 1,929 I. scapularis and 18 I. pacificus ticks collected in six provinces. Among I. scapularis, 22.3% were infected with B. burgdorferi, 11.8% with Babesia odocoilei and 4.3% with Anaplasma phagocytophilum. Fewer than 1% were infected with each of Borrelia miyamotoi (0.7%), Babesia microti (0.1%) and Powassan virus (0.1%).

As the risk of infection with tick-borne diseases continues to grow in many parts of Canada, monitoring trends in infection prevalence and the geographical range expansion of ticks provides essential data to inform public health actions and messaging.