Dogs Don’t Die Just in Hot Cars—Exertional Heat-Related Illness (Heatstroke) Is a Greater Threat to UK Dogs

SIMPLE SUMMARY: Heat-related illness (often called heatstroke) is a potentially fatal condition inflicted on dogs that will become more common as global temperatures rise. Understanding why dogs develop heatstroke can help to refine prevention strategies through owner education and societal changes. This study aimed to determine the most common triggers of heat-related illness in UK dogs, and which types of dogs were at most risk. We reviewed the veterinary records of over 900,000 dogs and identified that exercise was the most common trigger of heat-related illness in dogs. We also found that heatstroke caused by exercise was just as likely to kill as heatstroke from a hot car. Male dogs and younger dogs were more likely to develop heat-related illnesses triggered by exercise. Older dogs and flat-faced dogs were at greater risk of developing heat-related illness just by sitting outside in hot weather. Any dog can develop heatstroke if left in a hot car, but flat-faced breeds were particularly at risk. As the world gets hotter, we need to include our canine companions in our strategies to stay cool, as they can suffer fatal consequences when we fail to keep them safe. ABSTRACT: Heat-related illness will affect increasing numbers of dogs as global temperatures rise unless effective mitigation strategies are implemented. This study aimed to identify the key triggers of heat-related illness in dogs and investigate canine risk factors for the most common triggers in UK dogs. Using the VetCompass(TM) programme, de-identified electronic patient records of 905,543 dogs under primary veterinary care in 2016 were reviewed to identify 1259 heat-related illness events from 1222 dogs. Exertional heat-related illness was the predominant trigger (74.2% of events), followed by environmental (12.9%) and vehicular confinement (5.2%). Canine and human risk factors appear similar; young male dogs had greater odds of exertional heat-related illness, older dogs and dogs with respiratory compromise had the greatest odds of environmental heat-related illness. Brachycephalic dogs had greater odds of all three types of heat-related illness compared with mesocephalic dogs. The odds of death following vehicular heat-related illness (OR 1.47, p = 0.492) was similar to that of exertional heat-related illness. In the UK, exertional heat-related illness affects more dogs, and kills more dogs, than confinement in a hot vehicle. Campaigns to raise public awareness about heat-related illness in dogs need to highlight that dogs don’t die just in hot cars.