Professor Johan Schoeman of the Department of Companion Animal Clinical Studies (CACS) at the Faculty of Veterinary Science and South African, RCVS and EBVS® European Veterinary Specialist in Small Animal Internal Medicine discusses the health issues that may arise for dogs during a heatwave, signs of heat stress and emergency treatment that should be administered in the case of heatstroke.

What sort of health issues are dogs at risk of during a heatwave?

Do not lock your animal in a car that’s parked in direct sunlight, as this can have fatal consequences. Don’t take dogs with thick coats (like Siberian huskies) or those with short noses (like bulldogs) on long walks in direct sunlight during the current heatwaves affecting the country. Dogs cannot sweat, and the only way in which they can dissipate heat is through panting. Many short-nosed breeds have very thin tracheas (windpipes) and cannot rid themselves effectively of excess heat. These thick coats and maladapted respiratory systems make these dogs prone to heatstroke. 

The central nervous system is often affected. Neuronal injury and cell death, the development of brain oedema and the occurrence of localised areas of brain haemorrhage can lead to seizures, coma and death. Signs of cerebellar (small brain) dysfunction may also develop and remain permanent in animals that survive. 

What are the signs of heat stress in animals?

An animal with heatstroke will present with extreme panting, hypersalivation and darkened mucous membranes in an attempt to decrease the markedly elevated temperature.

What does emergency treatment entail?

The key to recovery from heatstroke lies in early recognition and treatment. Treatment should be instituted at home by the owners whenever possible. Following initial phone consultation, a dog should be sprayed with cold water before transporting it to the veterinary clinic. All the car windows should be left open on the way to the clinic, as this will help to increase convective heat losses from the dog. On presentation at the clinic, the dog should be sprayed down with cold water and not immersed in a cold water bath. Massaging the animal will help to increase blood flow, vasodilation  and cooling. An ice-water bath is usually not necessary and may actually decrease cooling of the animal because of vasoconstriction and decreased cutaneous blood flow. Furthermore, application of ice water may induce a shivering response, which is a heat-generating mechanism. Cold water enemas have been suggested as a means of decreasing body temperature, but this approach is often not necessary and inhibits monitoring.

The prognosis in heatstroke victims is variable and depends on the presence or absence of any underlying disease that may have precipitated the hyperthermia. In any case, the prognosis is guarded to poor, given the potential for life-threatening complications. Heatstroke victims will often have residual neurologic deficits and are predisposed to recurrent episodes of hyperthermia. Animals that recover are those whose temperatures are returned to normal early in the course of the disease, since the longer the animal remains hyperthermic, the greater the damage that occurs to vital organ systems.