Published: 26 Mar 2021 | Last Updated: 26 Mar 2021 15:08:51

More than half of dogs that are taken to veterinary clinics with severe heatstroke go on to die from the condition, according to a new study.

Image credit: Nottingham Trent University

The risks to dogs are much lower, however, if these cases are detected and managed earlier, veterinary researchers at Nottingham Trent University and the Royal Veterinary College found.

They are now urging owners to be more vigilant in watching out for the early, more mild clinical signs of heatstroke in their dogs so they can take action before their pet’s condition worsens and becomes potentially fatal, particularly as the summer season approaches and temperatures start to rise.

The researchers examined anonymised clinical records of more than 900,000 UK dogs as part of the ‘VetCompass’ study.

They found that respiratory changes and lethargy were the two most common early signs of heatstroke. Heatstroke is becoming an increasing problem for dogs - particularly as global temperatures continue to rise – and cases are expected to become more common in the UK.

The researchers identified 856 heat-related incidents in their study that required veterinary care over a two-year period, making this the largest study on heatstroke ever carried out in the UK.

They found that 111 (14.0%) of these heatstroke cases were categorised as severe, with these dogs showing a range of serious clinical signs such as seizures, vomiting and loss of consciousness. Of these severe cases, 63 (57%) went on to die of the condition.

Once dogs lost consciousness at that severe stage, they were 37 times more likely to die, the researchers found.

Dogs with the early and milder forms of heatstroke generally showed respiratory changes (seen in 69% of mild cases), such as laboured breathing, and lethargy (seen in 48% of mild cases) where dogs displayed tiredness or changes in behaviour such as not wanting to exercise.

Almost all dogs that presented for veterinary care with these early signs survived (98%).

This is key, the researchers say, because earlier recognition of these milder signs allows owners to take decisive action such as contacting their veterinary practice, giving their dog a drink or cooling it with water, bringing it inside and stopping exercise.

The work, which is published in the journal Scientific Reports, has also led to the development of a new grading tool that enables veterinarians to reliably categorise heatstroke cases into mild, moderate or severe grades. This information will assist veterinarians to tailor their clinical management plans to match the clinical needs of these dogs and therefore to improve their chances of a successful outcome.

“Heatstroke is a potentially fatal condition inflicted on dogs and is expected to become even more common as temperatures continue to rise,” said lead researcher Emily Hall, a veterinary surgeon in Nottingham Trent University’s School of Animal, Rural and Environmental Sciences.

She said: “If the dog is not quickly cooled or treated by a veterinary surgeon, its condition can rapidly worsen. It is vitally important that owners know to take action when their dogs show these milder signs, in order to prevent progression to heatstroke. Once dogs get to that severe stage, it’s really a coin toss as to whether they will survive.

“We hope the grading tool will be useful for veterinary surgeons as there has never been a clear definition for dogs such as this.”

Dr Dan O’Neill, co-author and senior lecturer in companion animal epidemiology at the Royal Veterinary College, said: “This new information on heatstroke signs and the novel VetCompass Grading Tool empowers owners to understand and take back control of heat-related illness in their dogs. This is especially important for flat-faced breeds such as English and French Bulldogs and Pugs that are at extra risk.

“Owners can rapidly learn how to avoid the triggers for heat-related events for their own dog and therefore how to prevent future events. Owner empowerment is the key to improving dog welfare.”

Dogs Trust, the UK’s largest animal welfare charity, provided a Canine Welfare Grant for the research project.

Paula Boyden, Dogs Trust Veterinary Director, said: “Each year, Dogs Trust considers grant applications from institutions such as the Royal Veterinary College and Nottingham Trent University for research projects which positively impact dog welfare and we were delighted to be able to support this important work.

“Dogs Trust has campaigned for many years on the ‘Hot Dogs’ issue, providing guidance to owners to help them look after their dogs in hot weather, but sadly every year we hear of dogs dying as a result of heatstroke. It is truly worrying that the research has found that over half of dogs taken to veterinary clinics with severe heatstroke go on to die from the condition.

“We hope that with the research showing the risks to dogs are much lower if heatstroke is detected and managed early, raising awareness and knowledge of the early warning signs amongst owners, and encouraging prompt attention, will help avoid the heart-breaking situation of their dog becoming severely ill or dying as a result.”

Previous research by the team behind this new study showed that excessive exercise was responsible for three-quarters of heatstroke cases in dogs and that flat-faced breeds such as bulldogs and pugs – were most at risk of developing heatstroke.

The latest study is part of the ongoing VetCompass research programme at the Royal Veterinary College, that aims to improve companion animal welfare and was supported by a Dogs Trust Canine Welfare Grant.