Hyperthermia – overheating

Guinea Pigs originate from South America where they still live in the wild today. In the wild, guinea pigs tend to make their habitats in rocky areas, grasslands and forests. They are used to coping with relatively high environmental temperatures, upwards of 22°C/71.6°F, providing they have access to shade and fresh water. However, they can rapidly overheat, and apart from their ears and the soles of their teeth, they are densely furred, so find cooling down, when too hot, difficult.

Guinea pigs can regulate their body temperature using their ears to lose heat and seeking shade to keep cool. However, unlike other animals like dogs, guinea pigs can’t pant to regulate their body temperature. Therefore, they are very susceptible to their body overheating, or hyperthermia. Mouth breathing in the guinea pig is extremely serious and a life-threatening sign that the guinea pig is struggling to breathe.

If the guinea pig’s body temperature rises over 40°C/104°F, they are very likely to suffer from hyperthermia. A normal body temperature is up to about 39.4°C/102.92°F.

Hyperthermia can have effects on many parts of the body, including the nervous and respiratory systems, the heart, digestive tract and kidneys, and can be rapidly, and often, fatal.

There are several risk factors for hyperthermia in guinea pigs.

Excessive heating of the guinea pig’s environment, eg on a hot sunny day (>22°C/71.6°F ambient temperature) without shade and drinking water. Direct sunlight, poor ventilation, high humidity and dehydration all predispose to hyperthermia. If the guinea pig is ill or elderly, or even if the companion bullies it, so it is unable to reach any available shade, they are more likely to succumb to it.

Drugs including some anesthetics can affect the guinea pig’s ability to regulate its body temperature although this normally results in hypothermia, which is why it is important after any anesthetic or sedation, to keep the guinea pig warm.

Excessive exercise, particularly if it involves stress, eg chasing a guinea pig to capture and handle it; exertion creates body heat. This could be a person chasing them, another guinea pig or a predator.

Stress and anxiety due to other causes, eg confinement in a vehicle or small carrying box or being in the presence of predators. Often guinea pigs are given small plastic hides and whilst they like these, if the guinea pig becomes trapped or unable to exist the hide, it will rapidly heat up inside, causing hyperthermia.

Heavily pregnant does, obesity, elderly guinea pigs, a thick hair coat, and underlying disease, eg heart disease or infection, are also all predisposing factors.

Several of these factors may combine in one instance.

Clinical signs may include:

• Extremities, eg ears and feet, are warm to the touch.
• Anorexia.
• Increase in breathing rate, with open-mouth breathing.
• In some cases, blood-tinged fluid from the nose and mouth.
• Dullness.
• Restlessness.
• Incoordination.
• If the guinea pig isn’t circulating enough oxygen then their mouth and nose will by cyanotic, ie blue-tinged.
• If allowed to progress, the guinea pig may collapse, have seizures, and die.

Hyperthermia is an emergency and treatment must be given rapidly.Call your veterinarian and take your guinea pig to your local veterinary clinic straight away for emergency treatment if advised to do so.

In the meantime, these simple steps can help reduce your guinea pig’s body temperature:

• Take your guinea pig out of the warm environment and place it into a cooler, well-ventilated area.
• If you have access to one set a fan, on a low speed onto them to help circulate the air around.
• Reduce body temperature SLOWLY; if this is done too quickly it can cause stress sending your guinea pig into shock which can be fatal.
• Wet the ears and feet and blow them with a hair drier or convection fan on a cold setting.
• Spray the body with cool water, in particular the belly area and between the back legs.

DO NOT PLACE WET TOWELS ON TOP OF YOUR GUINEA PIG. THIS WILL INSULATE THE WARM AIR AND WILL NOT AID COOLING.

If the guinea pig becomes more distressed, stop active cooling.

Check the temperature of your guinea pig’s environment; it should be between 16-21°C/60.8-69.8°F.

Ensure your guinea pig has accommodation which shelter it from excess temperatures, either heat or cold, and that it can move freely from a warmer area to a cooler area (and vice versa). In hot weather, fans or water sprays can help cool the environment. Bear in mind that the sun moves around during the course of the day, so ensure that if left alone, the guinea pig will have shade throughout the day.

Obese or heavy-coated guinea pigs can have their hair clipped to reduce the risk of hyperthermia.

Avoid stressing your guinea pig by chasing it, especially in warm weather.