Mice – health

Information about disease prevention and signs of illness in mice.

Disease prevention

Disease control methods and internal and external parasite control programs should be developed in consultation with a veterinarian. All activities must be documented in the appropriate records.

It is important to maintain a program of control for both internal and external parasites and disease in all mice. When treating for internal and external parasites, all mice should be treated at the same time. These activities need to be documented in the appropriate records.

When using animal care chemicals, care must be taken and noted about the following:

  • Reading all labels
  • Maintaining appropriate storage
  • Adhering to withholding periods
  • Determining the weight of the animals to be treated
  • Determining the correct dose rate
  • Using protective clothing if required
  • Using the correct equipment for application
  • Disposal of chemical containers
  • Documenting the dose, chemical name, batch number, expiry date, withholding period, identity of animal(s) administered to and date of administration.

Quarantining and isolating new mice from existing mice is an essential part of controlling illness and disease amongst mice. New mice should be quarantined for four weeks and need to be closely monitored for any signs of illness or disease. It is common for mice to harbour diseases without showing any signs of illness.

Regular cleaning of the housing environment greatly influences the risk of illness and disease. Mice are very sensitive to the effects of urinary ammonia that can cause irritation to the lining of their respiratory system. Bedding must be changed at least twice a week as ammonia may rise to dangerous levels and impact negatively on the mice’s health. Ventilation is also essential for control of ammonia build up.


Pet mice can easily become overweight and obese if their diet is not managed correctly. Mice must not be fed lollies, cakes and sweets. Commercial mouse pellets are recommended and can be supplemented with fresh vegetables, cereals, whole grain breads, fruit and low fat yoghurt.

Overgrown incisors

The incisors (front gnawing teeth) of mice continue to grow throughout their life. In the wild these teeth are worn by chewing on hard objects, however caged mice without this opportunity often develop overgrown teeth.

Hereditary abnormalities of the jaw resulting in improper meeting of the upper and lower jaw can also lead to tooth overgrowth. Overgrown teeth can injure the inside of the mouth, causing pain to the mouse and sometimes impacting on their ability to eat. Teeth need to be checked regularly and trimmed if necessary by a veterinarian. If unsure of the correct length of the mouse’s teeth, seek veterinary advice. A diet containing raw, hard food and the availability of objects for chewing will decrease the chance of this problem.


Mice are very susceptible to developing tumours both internally and externally. These tumours present as lumps on the mouse’s body. If a mouse is showing signs of tumours, it must receive veterinary attention immediately.

Chronic murine pneumonia

This is a serious bacterial infection that commonly affects mice. Signs and symptoms include sniffling, sneezing, squinting, red brown tears, rough coat and laboured breathing. When the inner ear is involved, the mouse will usually develop quite a severe head tilt. This disease has a chronic, long-lasting effect and must be treated with antibiotics by a veterinarian as soon as symptoms are noticed. The bacteria responsible for the disease is highly contagious and can be carried by mice without them showing symptoms, as well as passed from mother to young, and in the air.

External parasites

Mice can host a variety of external parasites including mites, fleas and ticks. Mice need to be checked regularly for signs of infestations. Animal safe insecticides are available from your veterinarian to treat these infestations. All external parasites can be transmitted directly from one animal to another.

Intestinal parasites

Tapeworms and pinworms are the most common parasites that effect mice. They usually go undetected unless they are present in very large numbers. Symptoms include licking/scratching of the rear, weight loss, lethargy and constipation. A veterinarian is able to examine faeces to identify the type of worms that are infecting the mouse, and can then assign an appropriate treatment. Great care should be taken when handling mice to ensure that handlers, especially children’s hands are always thoroughly washed after handling mice and when disposing of their faeces. Transmission of parasites to human is unlikely, but possible.

Signs of illness

A healthy mouse has clear and wide-open eyes with upright ears and fur that is dense and sleek. Mice will always sleep in a foetal position. If they are sleeping in a stretched out, extended position, this may be a sign that they are ill.

Any of the following symptoms may be an indication of illness:

  • Reluctance to move
  • Unkempt, erect coat
  • Discharge from the eyes, nose, urinary or genital organs
  • Coughing and sneezing
  • Constant scratching, lack of balance, stumbling or stiff legged gait, soft faeces with an unpleasant smell
  • Loose skin, which is a sign of weight loss
  • Prostration, extension, bumps or lumps, which can indicate possible growths or abscesses.

Animals with any of these symptoms should be immediately isolated from other animals and their cages fully disinfected. A failure to thrive or grow is another sign of illness.

If the cause of ill health cannot be identified or corrected, seek assistance from a veterinarian. Any signs of illness or injury, and treatment given, must be documented in the appropriate records.


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