Canada has, and is forecasted to continue to, experience significant changes to its climate. These climatic changes have impacted many different facets of our lives, and non-vertebrate animals have not been immune to these shifts.

While it is easy to generalize these changes, the most important aspects are prolonged periods of warm temperatures and increased humidity, as these conditions can support the survival, reproduction, and activity of Ixodes spp. ticks. With higher tick abundance and longer periods of activity, there is an increase in the risk of companion animal tick acquisition, which, in turn, can lead to pathogen exposure and disease development.

The infamous blacklegged tick (deer tick), Ixodes scapularis, has shown considerable range expansion in Canada. This tick and its western counterpart, Ixodes pacificus, can transmit the causative agent of Lyme disease, Borrelia burgdorferi, and the causative agent of anaplasmosis, Anaplasma phagocytophilum.

In dogs, Borrelia burgdorferi infection can manifest as lameness, fever, or anorexia, but many dogs will remain clinically normal. The impact of infection with B. burgdorferi in cats is not clear at this time. Dogs and cats infected with Anaplasma phagocytophilum may present with fever, lethargy, and inappetence.

Given these ongoing changes in tick populations and the risks they can pose to companion animal health, it is important to have regionally specific information on tick distribution and pathogen prevalence to generate evidence-based recommendations for prevention.

The data

The Canadian Pet Tick Survey (CPTS), which was sponsored by the Ontario Veterinary College (OVC) Pet Trust Fund, was a year-long study through which participating veterinary clinics across Canada submitted ticks from companion animals.

In total, 94 veterinary hospitals participated from all provinces and more than 4500 ticks were received. Accompanying each tick submission was a brief questionnaire that ascertained information, including the date of tick removal and suspected location of acquisition. All ticks were identified at the University of Guelph (U of G), and Ixodes scapularis and I. pacificus were subsequently tested via molecular methods for B. burgdorferi and A. phagocytophilum.

While this study is useful for highlighting patterns and emerging trends, it is important to remember results will be influenced by several factors, including the location of participating clinics and the level of interest in the study.

Where and when were ticks found?

Ixodes scapularis submissions were received from central and eastern Canada, especially southeastern Manitoba, southeastern Ontario, southern Québec, New Brunswick, Nova Scotia, and Prince Edward Island. Many of these locations have been previously identified as ‘high-risk’ regions for Ixodes scapularis acquisition. Submissions exhibited a bimodal peak in the spring (particularly from April to May), and the fall (particularly October).

All Ixodes pacificus submissions were received from southern British Columbia, concentrated to the Vancouver Island region. Ixodes pacificus had prolonged activity, with submissions received nearly every month of the year (with higher numbers in April and May).

We also received many Ixodes cookei submissions. This tick species, also known as the groundhog tick, was submitted from southern regions of Ontario, Québec, and throughout New Brunswick. Groundhog tick submissions were submitted from April through October, with a submission peak in May and June.

Overall, we found Ixodes spp. are well-distributed in the country and active throughout many times of the year, depending on the area and species of tick.

What pathogens were they carrying?

The findings were relatively consistent with ongoing tick surveillance conducted via public health and other research endeavours.

Borrelia burgdorferi was detected in Ixodes scapularis across eastern Canada, with the highest estimates (i.e. greater than 20 per cent) in southern Manitoba, eastern Ontario, southern New Brunswick, and southeast Nova Scotia. In contrast, A. phagocytophilum was either absent or detected at a low level (i.e. less than five per cent), except for southern Manitoba, eastern Ontario, and Prince Edward Island, where it was slightly higher (i.e. between five and 10 per cent). This may indicate potential areas of emerging risk.

The pathogen risks associated with Ixodes pacificus have historically been much less (i.e. less than one per cent). Borrelia burgdorferi was found at a lower infection prevalence in our study compared to other areas, but higher than typically found in British Columbia. This warrants ongoing surveillance.

Driving home the importance of tick prevention

Preventative measures should be taken by pet owners to limit the chance of tick acquisition for themselves and their pets. While the first line of defence is avoidance of tick habitat, this is often not practical for pet owners, nor in the best interest of their pets, given the health and well-being benefits of being in nature.

Performing thorough tick checks following any outdoor activity is an excellent way to find and remove these parasites promptly. If clients are limited on time, it can be helpful to tell them to pay particular attention to the head, ears, and collar region of their pets, as these are common areas of tick attachment.

Veterinary-prescribed tick prevention products offer strong coverage for the most common tick species encountered in Canada. A ‘one-size-fits-all’ approach to tick prevention use does not work in a country as vast as Canada, with diverse climates and habitats. Utilizing regionally specific data, such as what is available through the Canadian Pet Tick Survey or provincial public health organizations, is invaluable in generating evidence-based recommendations for your clinics.

Sydney DeWinter, BSc., MSc., is a PhD student at the Ontario Veterinary College (OVC), University of Guelph. She recently completed her MSc. at this institution, where she analyzed passive surveillance data to report on several epidemiological aspects of Ixodes ticks in Canada. DeWinter is trained as an epidemiologist and has experience building multi-level logistic regression models and projecting spatial data. Her research interests include vector-borne zoonoses and infectious disease epidemiology and ecology, and implementation of the One Health approach. She can be reached at sdewinte@uoguelph.ca.

Katie Clow, DVM, PhD, is an assistant professor at OVC. Her research focuses on the ecology and epidemiology of vector-borne and zoonotic diseases, with an emphasis on companion animals. She is passionate about applying a One Health approach in her research. Dr. Clow can be reached at kclow@uoguelph.ca.

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