Environmental Toxic Exposures Using Companion Animals as an Indicator of Human Toxicity: A Case Report and Discussion

Hundreds of years ago, humans realized that animals could be used as surrogate indicators of toxic environmental exposures, as a tool to measure risk to human health. The classic example is coal miners bringing canaries into coal mines. The respiratory rate and metabolism of the animal resulted in toxic signs of injurious gases in the environment before humans were injured. Occasionally, modern diagnosis of cryptic toxic exposures can be aided by the discovery of such features in the history.

We introduce this review using a case of inhalational mercury toxicity involving humans and companion animals-household dogs and cats. The death of exposed pets prior to the mounting of symptoms in the exposed humans was advance warning of the near-fatal presentation to come. Our objective was to review and characterize the state of the literature on companion animals as sentinel species.

We reviewed 748 articles, which resulted in 25 selected for inclusion in this narrative review. We detail examples of companion animals (household dogs, cats, and birds) affected by toxic exposures in acute and chronic ways-acting as harbingers of impending human toxicity in acute or chronic settings. Mercury, lead, Teflon, herbicide, and asbestos exposures present with predictable signs and symptoms in companion animals prior to presenting in humans. Identifying the toxidrome in a companion animal allows for subclinical identification of exposure and consequences in the human that permits early treatment and intervention.

Companion animals, when similarly exposed to toxic substances as humans regarding route, dose, and chronicity often mount symptoms and signs in advance of humans. This phenomenon allows the clinician to identify occult exposure, test, and treat while human disease is mild or still subclinical.