As climate change causes global temperatures to rise, heat-related illness, a potentially fatal condition in dogs, will become an ever-greater threat. this study aimed to report the incidence, fatality and canine risk factors of heat-related illness in UK dogs under primary veterinary care in 2016. The VetCompass tM programme collects de-identified electronic patient records from UK veterinary practices for research. From the clinical records of 905,543 dogs under veterinary care in 2016, 395 confirmed heat-related illness events were identified. The estimated 2016 incidence of heat-related illness was 0.04% (95% CI 0.04-0.05%), with an event fatality rate of 14.18% (95% CI 11.08-17.96%). Multivariable analysis identified significant risk factors including breed (e.g. Chow Chow, Bulldog and French Bulldog), higher bodyweight relative to the breed/sex mean and being over two years of age. Dogs with a brachycephalic skull shape and dogs weighing over 50 kg were also at greater risk. As we move into an ever-warmer world, veterinary professionals may need to include resistance to heat-related illness amongst their rationales when advising owners on breed selection. Breeding for good respiratory function and maintaining a healthy bodyweight should be considered key welfare priorities for all dogs to limit the risk of heat-related illness. Climate change is listed among the World Health Organisation's top ten threats to Global Health in 2019, with heat-related illness (HRI) predicted to contribute towards an additional 250,000 human deaths annually by 2030 1. HRI is a progressive disorder of animals and man caused by core body temperatures that rise above homeostatic limits, resulting in metabolic disturbances 2. This can lead to decreased cardiac output, fatigue of heat dissipation mechanisms, organ failure and ultimately death 2-4. Animal welfare organisations in the United Kingdom (UK) and Australia have reported increasing numbers of calls about animals trapped in hot environments over recent years 5,6. As the frequency and severity of heat waves is predicted to increase, there is an urgent need for better evidence-based guidance on the risk factors and early recognition of HRI to improve prevention and treatment strategies for both humans and animals 3,7. A deficiency of reliable and current data on the diagnosis, treatment and fatality rate of HRI is a key barrier to mitigating HRI risks in both humans and dogs 8. The classical terminology used to define HRI varies, but typically includes terms that describe progression from heat stress, through heat exhaustion to heatstroke 2. However, these classical terms lack clear explicit definitions and are often used interchangeably as synonyms, leaving their usage open to individual interpretation that creates a confused medical and veterinary literature 3. A novel HRI scoring system has been proposed for use in humans, acknowledging that patients can progress through the stages of disease severity depending on the duration and intensity of heat exposure and effectivenes...

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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 VetCompassTM 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.

Increasing numbers of people are running with their dogs, particularly in harness through the sport canicross. Whilst canicross races are typically held in the winter months, some human centred events are encouraging running with dogs in summer months, potentially putting dogs at risk of heat related injuries, including heatstroke. The aim of this project was to investigate the effects of ambient conditions and running speed on post-race temperature of canicross dogs in the UK, and investigate the potential risk of heatstroke to canicross racing dogs. The effects of canine characteristics (e.g. gender, coat colour) were explored in order to identify factors that could increase the risk of exercise-induced hyperthermia (defined as body temperature exceeding the upper normal limit of 38.8°C).108 dogs were recruited from 10 race days, where ambient conditions ranged from - 5 to 11°C measured as universal thermal comfort index (UTCI). 281 post race tympanic membrane temperatures were recorded, ranging from 37.0-42.5°C. There was a weak correlation between speed and post-race temperature (r = 0.269, P < 0.001). Whilst no correlation between any single environmental factor or UTCI and post-race temperature was found, the proportion of dogs developing exercise-induced hyperthermia during the race increased with UTCI (r = 0.688, P = 0.028). Male dogs (χ(1) = 18.286, P < 0.001), and dark coated dogs (χ(2) = 8.234, P = 0.014), were significantly more likely to finish the race with a temperature exceeding 40.6°C. Prolonged elevati°n of body temperature above this temperature is likely to cause heatstroke. At every race dogs exceeded this critical temperature, with 10.7% (n = 30) of the overall study population exceeding this temperature throughout the study period. The results suggest male dogs, dark coloured dogs, and increased speed of running all increase the risk of heatstroke in racing canicross dogs. Further research is required to investigate the impact of environmental conditions on post-race cooling, to better understand safe running conditions for dogs.

Running header:Comparison of rectal and tympanic membrane temperature in exercising dogs. AbstractThe ability to monitor body temperature in athletes at risk of hyperthermia is essential in all species. Currently, the only commonly accepted temperature monitoring site in dogs is the rectum. This is impractical in field situations as it takes time, requires additional handlers to restrain the dog and is not tolerated by all animals. Tympanic membrane temperature (TMT) monitoring may provide a rapid measure of body temperature to facilitate identification of heat stress and heat stroke in canine athletes. In human studies, TMT diverges from rectal temperature (RT) as body temperature increases during exercise induced hyperthermia so is not recommended for monitoring human athletes. If the same divergence occurs in dogs, TMT may not be suitable for use when monitoring the temperature of canine athletes.The aim of the study was to determine if TMT diverged from RT following exercise in healthy dogs. 24 healthy dogs were recruited to the study. Body temperature was measured using a veterinary auricular infrared thermometer (VetTemp) to record tympanic membrane temperature and an electric predictive rectal thermometer. Temperatures were recorded pre and post exercise in a non-clinical setting, familiar to the dogs.The mixed model approach showed that exercise had no effect on the difference between RT and TMT (F(1,201) =0.026, P=0.872). The overall mean difference of RT minus TMT was 0.39°C (n = 116). 68.4% of readings fell within the accepted 0.5°C difference in temperature recording method.In line with previously reported TMT to RT comparison studies in dogs, this study found that TMT measured consistently lower than RT. Using a correction factor of 0.4°C minimised the difference. The hypothesis that dogs would show greater differences between TMT and RT following exercise was not supported, suggesting that TMT could be used to monitor body temperature in exercising dogs where RT is not possible.