Common Diseases of Guinea Pigs, Mice and Rats

Common Diseases of Guinea Pigs, Mice and Rats

Common diseases that affect pet rodents (guinea pigs, rats and mice) include respiratory diseases, anorexia and lethargy, overgrown teeth and tumours.

Respiratory infections

Respiratory infections are common and signs include discharges from the nose and eyes. With more severe infections you may notice wheezing, coughing, and open-mouthed breathing if pneumonia is present. Sick animals often stop eating and become lethargic.

Bordatella is a bacterium that causes respiratory disease in guinea pigs and can be fatal. In rats and mice, respiratory disease is often caused by a mycoplasma, another type of bacterium. Regardless of the cause, respiratory infections are common and can be prevented by keeping pet rodents in a clean, dry and warm environment and avoiding overcrowding.

Anorexia and lethargy

Anorexia and lethargy are not specific diseases, but they are the most commonly shown signs of illness in rodents. Anorexia (not eating) and lethargy (lack of energy) confirm that the animal is sick but do not mean you can tell the different diseases apart, such as pneumonia, cancer, kidney or liver failure. The sooner your vet sees your pet when it shows these signs, the sooner the correct treatment can be started and the better the chances of a full recovery.

Overgrown teeth

Overgrown teeth can occur in all rodents as their teeth grow continuously throughout their lives. If the teeth don’t wear down properly, they can become too long and not meet properly. This can cause your pet to stop eating and you may notice it drooling or having a wet chin ('slobbers').


Cancer is most often seen in pet rodents as tumours on the body, like mammary tumours. In rats and mice the mammary glands extend along the back and sides so breast cancer can appear as a lump anywhere on the body.

Treatment of rodent diseases

  • Respiratory diseases are treated with antibiotics provided by your vet. All pet rodents are sensitive to certain antibiotics, which can cause stomach upsets and diarrhoea, and some can be fatal. Never use antibiotics left over from another pet and always consult your vet first before using any medication.
  • Overgrown teeth need to be trimmed and this is done under anaesthesia by your vet with a rotating burr. Using nail clippers or wire cutters can cause broken teeth and lead to infection. Preventing the problem by providing wood blocks for your pet to chew is far better.
  • Tumours can be removed surgically under anaesthesia, which is best done while the tumour is still small.

Prevention of rodent diseases

Maintaining good hygiene, a proper diet and a stress free environment are important factors in preventing most diseases in pet rodents.