Epidemiology, Triggers, and Risk Factors of Canine Heat-Related Illness

Heat-related illness (HRI), commonly referred to as heatstroke, is a potentially fatal condition in dogs arising when thermoregulatory mechanisms fail to maintain normothermia. Increasing ambient temperatures, urbanisation, and breed preferences have contributed to a rising incidence, making awareness essential in veterinary practice^1,2. 

Primary Triggers 

HRI in dogs is broadly classified into two categories: environmental and exertional. Environmental HRI occurs due to exposure t2o high ambient temperatures, such as confinement in poorly ventilated spaces, including vehicles or indoor environments. Exertional HRI is associated with physical activity and may develop even in moderate climatic conditions¹. 

Epidemiological data from the UK indicate that exertional HRI accounted for approximately 74.2% of cases presenting to primary care settings, often following low- to moderate-intensity exercise¹. Notably, cases are not restricted to peak summer months and may occur year-round. 

Wet bulb globe temperature (WBGT), which incorporates temperature, humidity, radiant heat, and airflow, is a more accurate indicator of environmental heat stress than ambient temperature alone. Mean WBGT associated with exertional HRI events has been reported at 16.5°C, reinforcing that risk exists even under seemingly mild conditions ². 

Additional triggers include confinement in warm buildings and exposure to stressful environments such as veterinary clinics or grooming facilities, where thermal load and anxiety may compound risk¹. 

Breed and Conformation Risks 

Breed predisposition is a significant factor. Increased risk has been reported in breeds such as Chow Chow, Bulldog, French Bulldog, Pug, Dogue de Bordeaux, Greyhound, Cavalier King Charles Spaniel, English Springer Spaniel, and Golden Retriever³. 

Brachycephalic breeds demonstrate elevated susceptibility due to compromised respiratory efficiency, limiting effective heat dissipation through panting ⁴. 

Age, Bodyweight, and Comorbidities 

Age-related variation in risk has been observed. Dogs under two years of age are more likely to develop exertional HRI, potentially reflecting higher activity levels. Conversely, dogs over 12 years are more susceptible to environmental HRI, likely due to age-associated decline in thermoregulatory capacity¹. 

Increased bodyweight and obesity are also associated with higher risk, whereas dogs weighing under 10 kg appear comparatively less susceptible³. 

Clinical Implications 

Recognition of these epidemiological patterns enables veterinary professionals to identify at-risk populations, guide client education, and implement preventive strategies. Proactive risk assessment is essential to reducing morbidity and mortality associated with canine HRI. 

References  

1. Hall EJ, Carter AJ, O’Neill DG. Dogs Don’t Die Just in Hot Cars-Exertional Heat-Related Illness (Heatstroke) Is a Greater Threat to UK Dogs. Animals (Basel). 2020a;10(8):1324. https://doi.org/10.3390/ani10081324   
2. Hall EJ, Carter AJ, Chico G, et al. Risk Factors for Severe and Fatal Heat-Related Illness in UK Dogs-A VetCompass Study. Vet Sci. 2022;9(5):231. https://doi.org/10.3390/vetsci9050231    
3. Hall EJ, Carter AJ, O’Neill DG. Incidence and risk factors for heat-related illness (heatstroke) in UK dogs under primary veterinary care in 2016. Sci Rep. 2020b;10(1):9128. https://doi.org/10.1038/s41598-020- 66015-8 https://www.nature.com/articles/s41598-020-66015-8    
4. Davis MS, Cummings SL, Payton ME. Effect of brachycephaly and body condition score on respiratory thermoregulation of healthy dogs. J Am Vet Med Assoc. 2017;251(10):1160–1165. https://doi.org/10.2460/ javma.251.10.1160