Mouse Health

Some Usual Mouse Ailmens

Respiratory mycoplasmosis

Usual symptoms are coughing, sneezing, lethargy and in chronic cases clear weakening of general condition. When a mouse gets mycoplasmosis, its breath rattles. You should separate the sick mouse from the others so it won't give the other mice its disease. You should keep close eye on the mouse for a while. If it has only caught cold, it will get well. Antibiotics may relieve the symptoms, but the mycoplasmosis cannot be cured. Mouse that has mycoplasmosis but doesn't show symptoms can infect other mice. You should not use a sick mouse for breeding, as it may infect its young.

Eye infections

Sometimes a mouse's eye gets infected and you can see mucous secretion. The eye infection may be caused by dirty cage, the eye may have been stuck by hay, or some anti-parasite shampoo may have got into the eye during a wash. You can wipe the eye carefully using 'eye-solution' designed for dogs or cats, available in good pet shops. If you do not have eye solution at home, boil up some water, let it cool down and use it. If the eye infection doesn't heal, contact your vet.


For some reason tumours are more usual in does than in bucks. When a tumour is detected, it often grows very quickly. You shouldn't confuse a tumour with an abscess, which is sometimes seen in mice. An abscess doesn't grow quickly and it usually doesn't bother the mouse. It is better to euthanise a mouse with tumour, as the mouse suffers. Do not breed mice from strains where there are lots of tumours (especially at young age), because the tendency of getting tumours is hereditary.

Kinked tail

Kinked tail is a genetically hereditary defect in the tail. If you have a mouse with a kinked tail and you decide to breed from it, there will be more mice with kinked tail born. In shows, kinked tail is considered a fault. If your mouse has kinked tail due to an accident, it does not matter in breeding. Only those defects a mouse is born with, are hereditary.

Most common accidents

Mouse's tail can get hurt if the mouse is lifted from the tip of the tail. Lifting a mouse from the base of the tail doesn't hurt the mouse. While putting a mouse inside a small transportation/show box, watch out that the tail doesn't get stuck between the box and the lid. The tail could be permanently damaged. You should never lift a small baby mouse by its tail; it can get broken.

Small baby mouse (usually under 4 weeks of age) can get so scared when picked up that it jumps off of your hand. It doesn't understand that it is high above the ground. You should hold a mouse above the cage, low enough that it will not hurt itself if it decides to jump. Older mice who are used to be handled do not jump down.

At wintertime you have to take care that your mouse doesn't catch cold when you transport it. A mouse is much more sensitive to cold than, say, a rat. When a mouse feel chilly, its coat stands on its end and the tail feels cold. If a mouse gets too cold, it may even die. You should put a lot of bedding into a transportation box with shredded Kleenex on top of the bedding. This way the mouse can get under the paper, if it feels chilly


Serious tooth problems are rather rare on mice, but you should look into the mouse's mouth every now and then. Tooth checking should be done especially to young mice. Tooth problems divide usually into two categories: overgrowth and malocclusion (wrong position of teeth). Overgrowth can be caused from for example lack of hard things to gnaw. Sometimes it occurs even though there are hard substances to chew. In this case the reason can be a hormonal disorder.

Offering hard food to gnaw easily cures overgrowth. Hard bread, hard -shelled seeds and dog biscuits are good examples. Also dried branches of apple tree are excellent materials to chew.

If the damage has already been done, that is the teeth are already so long that the mouse cannot shorten them self, the teeth must be cut. For this you can use strong cat nail cutters. However, be careful not to cut too much! If you feel even a bit uncertain, ask help before cutting. Overgrown teeth have clear symptoms, so there is seldom any doubt in the need of cutting the teeth. The mouse drools and cannot eat properly, which causes the mouse to loose weight considerably.

Malocclusions are more serious problems. They are usually inherited, so you should never use a mouse with malocclusion for breeding! You should check the teeth of you breeding mice carefully before breeding from them. Malocclusion is usually accompanied by over growth, but you can slow the process down with regular trimming of the teeth. However, if the malocclusion is so bad that it hinders the normal life of the mouse and its eating, it is kinder to let it out of its misery - to put the mouse down.


Have you ever seen rash on a mouse? Mice can be allergic, too. In this article I will tell you about some rashes, funguses and other skin problems I have encountered.

Wheat Allergy

Some mice simply do not tolerate wheat. Other corn/grain are usually tolerated, but I have seen a couple of individuals who have become intolerant of other corn/grains as well. Allergy towards wheat may be inherited, so it is better not to use a mouse suffering from it to breeding.

Most common symptoms are loss of general condition, diarrhea and rash, which is scaly. The skin looks very dry and you can also see symptoms on the feet and the tail. First aid is changing the diet and grease the dry areas of skin. Vaseline or other unscented basic cream suitable for allergic people will do well.

Nickel Allergy

Allergy towards nickel can also be inherited. Symptom is rash. Usually it is seen first on the feet, tail and nose.

If your mouse is allergic towards nickel, you should remove everything metal from the mouse's abode. If the mouse is living in a cage, it should be moved to a plastic terrarium (glass tanks usually have metal screen tops). Note that a mouse that has nickel allergy, cannot have a water drinking bottle - you have to provide it with a water bowl (that is, if you do not manage to find a thoroughly plastic or glass water bottle).


Mouse can get fungus from for example other mice or through damaged skin, if it hasn't been treated. Discharge releasing, scaly fungus is usually seen on and around the ears, in the neck and on the front feet.

If you suspect a fungus infection, you should act quickly. Contact your vet immediately. Fungus infections can also be very hard to get rid of and the treatment takes a long time. Furthermore, they are painful for the mouse. Scratching reaction caused by itching may cause the ears to become totally torn. If it seems like the mouse does not get better in spite of treatment, you should consider putting an end to its suffering - putting the mouse to sleep. Treatment is prescription medicine available from vets. If the infection is very bad, your mouse will also get antibiotics. Treatment may take several months.

Severed Skin

You should always treat severed skin immediately because the possibility of getting an infection or fungus is at its greatest. Use non-smarting disinfectant to clean the area or powder / cream designed for sores. If the skin is badly infected, get antibiotics for the mouse.

Always separate a sick mouse from the others in order to avoid the disease spreading to others. Handle the sick mouse last and wash your hands thoroughly afterwards. If you do not know what is wrong with your mouse, take it to the vet. An experienced breeder can also recognize the disease, but only a vet can write a prescription for medicines.

The skin problems I have mentioned are only examples - others do exist but these are the most common ones. Always check your mice for ectoparasites, because they can cause the mouse to scratch its skin to sores.

You should not get scared because of these instructions. You should only remember to check your mouse's condition daily and take good care of its skin. Seed mixes are as such inadequate for your mice and because of that many fanciers feed their mice so called lab blocks. When the mice get use to eating lab blocks, you can give seeds as treats every now and then. Getting your mice to get used to new diet may be tricky business, but experienced breeders will give you advice if there are any problems. Do not hesitate to contact for example breeding counselor (if your local club has one). S/he is glad to help you with your questions.

Sendai Virus


Weight loss, rough coat, heavy breathing and matted eyes are all signs of a Sendai Virus infection. This is virus which is transmitted through respiratory tract, that is via air. Infection through direct contact is also possible.

The virus isn't common in the pet population, but it isn't unheard of. With pets, the only way you can usually get the virus to your mice is to get a mouse from somewhere where this virus was present. Most likely this kind of source is a feeder bin or pet shop mice of unknown origins. The infection can be lethal, but it is possible that adult and strong mice do not show signs at all. Nursing mice and weanlings do not survive an infection that well. If there is a secondary bacterial infection present, the result is a much more certainly lethal sickness. The bacterial infection in question may be relatively harmless in itself, but cause increased death rate when combined with Sendai.

What to do?

What you should do now, is to isolate the affected mice and their tank mates from your other mice. Preferably to another room. Always handle and feed your affected mice last, take a separate portion of food to keep with the mice who are ill or have been in contact with the mice who died. Don't take stuff back and forth from sick mice to the healthy. It is a good idea to use a mask when handling the sick mice, as according to my sources it is possible that we humans transmit an airborne disease from one animal to another in our nasal cavities for a certain length. (That is, you inhale the bacteria or virae into your nose when you are with sick mice spreading the disease when they breath and especially when they sneeze. Then, when you exhale near your healthy mice, they can get the disease.)

If you have rats, isolate them from your mice. Rats can get a Sendai Virus infection, too. The symptoms aren't as severe as with mice, but the infection does lower the rats' resistance to other illnesses. This means that other diseases may attack much more easily and with more severe results. Mycoplasma pulmonis combined with Sendai can be pretty fatal at worst. Furthermore, Mp is often present with other bacterial infections, like the CAR bacillus.

Is There a Cure?

There is no cure available for the Sendai Virus. Vaccine does exist, but I doubt it is available outside laboratories. You can ask your vet. However, you can treat the secondary bacterial infection with antibiotics. Sendai infection lowers the mouse's resistance to other diseases, so other illnesses may strike as well. If and when a mouse survives the infection it develops resistance towards the virus, lasting at least a year (which is in mice often long enough).

Where did it Come From?

Have you bought any new mice recently? If yes, where did they come from? If they came from a breeder, inform this person about the infection. If from a pet shop - the same thing. Make a big noise, if they won't listen to you. Pet shops are responsible for the animals they sell, even though they would like you to think otherwise.

How to Prevent Infections?

Always remember to isolate new pet mice from your other mice for at least two weeks, especially if you get a mouse from someone or some source you are not familiar with and do not know to be trustworthy. It is also good to keep other new pet rodents away from your mice, as rats, gerbils and hamsters (for example) can carry something your mice can't handle well (Sendai, Tyzzer's etc).

One note on beddings: The choice of beddings do not cause any illness as such, with the exception of allergies and possibly resulting asthma. However, with aromatic beddings the linings in the mouse's respiratory tracts may get thinner, enabling the bacteria and virae (sp?) to affect the mice more easily. If there are no bacteria or virae present, the mice will not fall sick to infectious diseases, no matter what beddings are used. This does not mean that it is OK to use cedar or pine - only that these alone do not cause diseases.