This week I saw Bob, a Labrador, who went for a walk with his owner in the bush. Bob was enjoying the sights and smells when he spotted a wallaby in the distance. This set off some primal urge and off he went after it. The wallaby disappeared with bob in hot pursuit. Three hours later he and his owner found each other again and Bob collapsed at her feet and had a seizure. Bob was middle aged and over weight and his strenuous burst of exercise was too much for him. He was seriously overheated.
When I saw him he was collapsed and salivating profusely, he was twitchy but no longer seizuring. His temperature was very high, nearly off the rectal thermometers scale. His owner had given some first aid by rolling him in a puddle. I lowered his temperature further by intravenous fluids, and some medications. Blood tests showed that he had fortunately not suffered any internal damage. Bob was very lucky.
Others have not been so lucky. Overheating often causes severe internal damage resulting in organ failure or brain damage. The breakdown products of the cooked tissues can also then damage the kidneys creating even more problems.
First aid consists of wetting the dog, giving it small frequent drinks of water, and putting the air-conditioning on full in the car as you drive it to the vet. Even if it seems only mild it is important to take your dog to the vet to help prevent the nasty after effects.
Prevention is mostly being aware of the temperature even on cloudy days and ensuring your dog has plenty of to drink and rests on its walks. If your dog likes to chase things then keeping it on a lead is also a good idea. Of course never leave your dog unattended inside a car or tied up in the sun.