Abstract
Background: Heat-related illness (HRI) can affect all companion animals and is likely to become more common as global temperatures rise. The misconception that HRI is primarily a result of dogs being trapped in hot cars, highlights a lack of awareness of HRI risk factors within the UK companion animal population.

Aim: This project aimed to review all species of small animal presentations of HRI to UK veterinary practices participating in the Small Animal Veterinary Surveillance Network (SAVSNET), describe the inciting triggers and seasonality of HRI events, and review the clinical grade of canine patients presenting with HRI.

Methods: Electronic consultation records were submitted by volunteer veterinary practices across Great Britain to SAVSNET. Cases were defined as animals presented for consultation with strong evidence of current, or recent heat induced illness during the study period (2013-2018).

Results: The HRI cases included 146 dogs, 16 cats, eight guinea pigs, three rabbits and one ferret. Of the 118 HRI cases with a recorded trigger, exercise was the primary trigger for dogs presenting (73.5%); seven (6.9%) canine HRI events followed vehicular confinement. Environmental HRI was recorded as a trigger for the remaining dogs (19.6%), and for all cats, guinea pigs, rabbits and the ferret. Brachycephalic breeds comprised 21.2% of canine HRI cases, and all rabbits were brachycephalic breeds. Dogs presented for HRI between April and October, with 42.5% during July, typically the UK’s hottest month of the year. Cats with HRI were presented between May and September, with 75.0% during June and July. The smaller companion species - ferrets, rabbits and guinea pigs – were presented during the UK’s summer months June to August.

Conclusion: This study highlights the risk of HRI to all pet animals during the UK’s warmer summer months (June to August). The findings support previous claims that exercise is the most common trigger of HRI in dogs, whilst environmental HRI (a hot ambient temperature) accounted for all HRI events in cats, rabbits, guinea pigs and ferrets. Both brachycephalic dogs and rabbits were overrepresented, adding further evidence that owners of these animals should be particularly vigilant for HRI during hot weather.

Key words: Canine heatstroke, Feline heatstroke, Heat-related illness, Heatstroke, SAVSNET