Beyond the Heat: Understanding Triggers and Epidemiology of Canine Heat-Related Illness

Heat-related illness (HRI), commonly referred to as heatstroke, remains a significant yet often underestimated emergency in small animal practice. While traditionally associated with dogs trapped in hot cars, emerging research highlights a broader and more complex epidemiological landscape. A deeper understanding of triggers and environmental dynamics is essential for veterinarians aiming to reduce morbidity and mortality associated with this condition. 

Heat-related illness occurs when a dog’s body temperature exceeds its capacity for thermoregulation, leading to systemic dysfunction. With rising global temperatures and shifting breed preferences, the burden of HRI is expected to increase, making early recognition and prevention strategies critical in veterinary practice¹. 

Reframing the Triggers: More Than Just Hot Cars 

One of the most clinically important insights from recent research is the distinction between environmental and exertional heat-related illness. 

Environmental HRI is triggered by exposure to high ambient temperatures, such as confinement in a hot vehicle, building, or poorly ventilated space. While widely recognized, this form represents only part of the problem. 

In contrast, exertional heat-related illness accounts for the majority of cases, contributing to 74.2% of HRI presentations in UK primary care settings². This finding challenges long-standing assumptions and underscores the importance of educating owners about exercise-related risks. 

Interestingly, many exertional HRI cases occur during low-intensity exercise, particularly in spring and summer. This suggests that dogs may not require extreme exertion or peak summer heat to develop HRI. Furthermore, cases have been reported year-round, indicating that environmental awareness must extend beyond seasonal advice. 

Understanding Environmental Risk: The Role of Wet Bulb Globe Temperature 

A key concept for clinicians is the wet bulb globe temperature (WBGT), which provides a more comprehensive assessment of environmental heat stress than ambient temperature alone. WBGT incorporates humidity, radiant heat, and wind speed, factors that significantly influence a dog’s ability to dissipate heat¹. 

The average WBGT associated with exertional HRI events in UK dogs was reported to be 16.5°C³, a temperature many owners may perceive as safe. This highlights a critical gap in public understanding and reinforces the veterinarian’s role in translating environmental risk into actionable advice. 

Urban Living and Emerging Risk Environments 

Urbanisation has introduced new risk factors for canine heat-related illness. Dogs living in urban settings are at increased risk, particularly due to heat retention in buildings and reduced airflow. Confinement in hot indoor environments has been identified as the third most common trigger for HRI¹. 

Additionally, veterinary clinics and grooming parlours themselves may inadvertently contribute to risk. These environments can be warm and stressful, and were implicated in approximately 4.6% of HRI events². This finding calls for heightened vigilance in clinical settings, including monitoring, ventilation, and stress reduction strategies. 

Clinical Implications for Veterinary Practice 

For practicing veterinarians, these findings translate into several practical considerations¹: 

• History-taking should actively explore exertional triggers, not just environmental exposure.  

• Client education must extend beyond “don’t leave dogs in cars”, addressing exercise timing, intensity, and environmental conditions.  

• Clinic protocols should include heat-risk assessment, particularly during warmer months or in high-risk patients.  

Furthermore, veterinarians should advocate for public awareness campaigns similar to the “Dogs Die on Hot Walks” initiative, which reflects the growing recognition of exertional heat-related illness. 

Bridging the Knowledge Gap 

A major challenge remains the disconnect between perceived and actual risk. Owners often underestimate the dangers of moderate temperatures or routine exercise. By incorporating epidemiological data into consultations, veterinarians can provide evidence-based guidance that resonates with clients. 

For example, explaining that most HRI cases occur during normal walks rather than extreme conditions can significantly influence owner behaviour. 

Conclusion 

The evolving understanding of canine heat-related illness demands a shift in both clinical practice and client education. Exertional triggers, urban environments, and subtle environmental factors all play a critical role in disease onset. By integrating these insights into routine care, veterinarians can move from reactive treatment to proactive prevention. 

Ultimately, improving awareness of triggers and environmental risk factors is not just about reducing case numbers; it is about safeguarding canine welfare in an increasingly unpredictable climate. 

Reference 
1. Bradbury J, Hall E, Carter A, O'Neill DG. Canine heat-related illness–new perspectives from recent research. Companion Animal. 2023 Jul 2;28(7):2-5. https://www.magonlinelibrary.com/doi/pdf/10.12968/coan.2023.0015 

2. 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. 2020 Jul 31;10(8):1324. https://www.mdpi.com/2076-2615/10/8/1324 

3. Hall EJ, Carter AJ, Chico G, Bradbury J, Gentle LK, Barfield D, O’Neill DG. Risk factors for severe and fatal heat-related illness in UK dogs—a VetCompass study. Veterinary Sciences. 2022 May 11;9(5):231. https://www.mdpi.com/2306-7381/9/5/231