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Summary of Public Health Ontario’s “Companion animals and tick-borne diseases: A systematic review”

Public Health Ontario (PHO) recently released an evidence-based review on the use of companion animals (dogs, cats, horses) as sentinels for human tick-borne disease, along with the role (and risk) companion animals represent to humans (specifically pet-owners) for these same disease concerns.


Key findings summarized by the review include:

1. Can companion animals be utilized as sentinels for human disease? 


Forty-four North American studies were identified (Canada: ON, BC) using companion animals as sentinels for human disease. The majority of these studies were on dogs as sentinels for human Lyme disease (19 studies, 2009-2016). 


Overall there was support for use of dogs for informing disease risk in people. One study found that a canine seroprevalence (test positive status) of greater than 5% was associated with increased human risk of Lyme disease (Mead et al., 2011).


2. Is companion animal ownership a risk factor for Lyme disease? 


The review identified 12 USA studies (cats (n=6), dogs (n=4), other companion animals (n=5)). Despite limitations to these reviewed studies (e.g., only adult populations looked at, no children), there was no evidence to support an increased risk of Lyme disease related to pet-ownership.



Why do dogs work as sentinels for human disease?


  1. Dogs are regularly (and easily) tested for exposure to multiple tick-borne pathogens (including the causative agent of Lyme disease, B. burgdorferi).

  1. The typical canine lifestyle consists of wandering happily through tick infested habitats, i.e. dogs commonly visit tick habitats and are easily exposed to ticks that bite, attach to dogs and subsequently transmit infection with B. burgdorferi or other common vector-borne pathogens.

  2. As such, canine seroprevalence (test positive status) aids in predicting areas where humans are more likely to become infected. This is in contrast to human Lyme disease surveillance which may lack reliability due to under-reporting.


This review provides another example of One Health in action, illustrating how human, animal (and environmental) health are interconnected. There is little doubt that man’s best friend and protector (i.e., the dog) continues to do what he or she does best…act as a warning bell for their beloved humans. Future research and collaboration between veterinarians, human health care providers and the general public will be needed to raise awareness regarding disease risk and prevention strategies with respect to ticks- for people as well as their pets.

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