Risk Factors for Severe and Fatal Heat-Related Illness in UK Dogs—A VetCompass Study

Abstract

Heat-related illness (HRI) is predicted to increase in dogs due to rising global temperatures. This study evaluated retrospective VetCompass veterinary clinical records to explore geographical variability and ambient conditions associated with HRI events in UK dogs, and report the intrinsic (canine) and extrinsic (location, trigger, ambient weather) risk factors for severe disease and fatal outcome in dogs affected by HRI. Dogs living in London had the greatest odds for developing HRI compared with dogs living in the North West (OR 1.9, 95% CI 1.31–2.74). The median ambient temperature on days of HRI events was 16.9 °C. For dogs with HRI, age, bodyweight and trigger were risk factors associated with severe disease. Age, skull shape and clinical grade of HRI presentation were associated with a fatal outcome. Whilst the majority of HRI events overall were triggered by exertion, the risk of severe disease was greater in situations where dogs could not escape the heat source (vehicular confinement), and the risk of death in HRI cases was greater for those dogs with reduced capacity to thermoregulate (older and brachycephalic dogs). These results highlight the need for better owner awareness of the factors that increase the risk of severe and fatal HRI, as a first stage in protecting canine welfare in the face of rising global temperatures.

Incidence and risk factors of heat‐related illness in dogs from New South Wales, Australia (1997–2017)

“…Death by heatstroke is likely to involve prolonged suffering, with potential sources of pain including the release of inflammatory mediators, damage to the gastrointestinal mucosa, ischemia, the stretching of organ capsules associated with acute congestion of abdominal viscera and rhabdomyolysis. The reported case fatality rate varies from 14% to 50% 14–19 . The actual fatality rate is likely to be higher as affected dogs may die before they can be presented to a veterinarian.…”

“…Dog‐related factors that may increase heat generation or reduce heat dissipation include obesity, large (>15 kg) bodyweight, brachycephalic conformation, thick hair‐coat, advanced age, pre‐existing airway, cardiovascular or neurologic disease. Specific dog breeds such as Chow Chow, Bulldog, French bulldog, Dogue de Bordeaux, greyhound, Cavalier King Charles Spaniel, Pug, English Springer Spaniel and Golden Retriever were found to be at increased risk of HRI compared with Labrador retrievers 19 . Poor clinical outcomes in affected dogs are associated with upper airway obstruction, prolonged seizures 3 and neurological dysfunction 20 .…”

“…The reported case fatality rate varies from 14% to 50%. [14][15][16][17][18][19] The actual fatality rate is likely to be higher as affected dogs may die before they can be presented to a veterinarian.…”

“…Specific dog breeds such as Chow Chow, Bulldog, French bulldog, Dogue de Bordeaux, greyhound, Cavalier King Charles Spaniel, Pug, English Springer Spaniel and Golden Retriever were found to be at increased risk of HRI compared with Labrador retrievers. 19 Poor clinical outcomes in affected dogs are associated with upper airway obstruction, prolonged seizures 3 and neurological dysfunction. 20 The prognosis of affected dogs is improved if veterinary care is sought early in the development of HRI and aggressive treatment is delivered.…”

Scientific and technical assistance on welfare aspects related to housing and health of cats and dogs in commercial breeding establishments

“…A limited ability to cool down efficiently can lead to rapid overheating, especially when exposed to high temperatures or humidity. Brachycephalic breed was found to be a risk factor for heatstroke in a retrospective study conducted to associate the heat-related illness events in UK with the dogs' characteristics and the environmental variables (Hall et al, 2022). The risk of a fatal outcome in dogs was indeed 12 times higher in dogs aged more than 12 years, and three-times higher if these dogs were brachycephalic when compared to mesocephalic dogs aged less than 2 years old.…”