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Common health issues in mice

Mites

Mites are a fairly common issue in small rodents, but can generally be prevented through good hygiene. Sometimes they will be brought in on bedding, but spotted early on are easy to treat and eradicate. Mites are visible as moving tiny reddy brown specks in the coat, and tend to congregate at the back of the neck and between the shoulders. If you see a judge holding their hand over a mouse for a few seconds, then removing it and staring closely at the coat, they are looking for mites. The mites are attracted to the warmth imparted by the judge's hand and will approach the surface of the coat where they can be seen more easily. Other signs of mites are sores at the back of the neck and shoulder area as well as sore ears caused by the mouse scratching.

An effective treatment, ivermectin is a broad-spectrum anti-parasitic that breaks the lifecycle of the mite and prevents new infestation. Treating once a week for three weeks with topical ivermectin should remedy the problem. If you are treating for mites you must thoroughly clean out the cage or box the mouse occupies as well to prevent reinfestation.

Mycoplasma ("snuffles" or "asthma")

Since the beginning of the mouse fancy breeders have struggled with breathing problems in their stock. Often referred to as "asthma" in the earlier part of the twentieth century as well as "wheezing" and "snuffles", modern fanciers are aware that they are dealing with respiratory infections and mycoplasmosis (M. pulmonis). This is a bacterium lacking a cell wall for which mice and rats are considered the natural hosts. Mice can transmit the illness by being in the same airspace as other mice, even to those in different cages.

Affected mice will make a chattering, clucking or snuffling noise when they breathe; in contrast healthy mice should not have audible breathing. Allergies or dusty bedding can also cause similar symptoms, so sawdust should never be used. High levels of ammonia (contained within urine) have been scientifically proven to increase the growth of M. pulmonis in the respiratory tract (Schoeb et al, 1982) so care should always be taken to keep habitats free from too much soiled bedding and substrate. Vitamin A and E deficiency can also have an influence (Tvedten et al, 1973), as can the inhalation of tobacco smoke (Wynder et al, 1968).

Although baytril (enrofloxacin), a broad spectrum antibiotic, is the treatment prescribed for mice by vets, in reality this is not particularly effective. If an infection is not caught early there is not usually much that can be done other than to remove the affected individual to prevent it spreading throughout the stud. Like several other illnesses of mice, the signs of lower respiratory infections include a hunched posture, ruffled coat and inactivity.

Tumours

PictureMouse with facial tumour
It is not uncommon for mice to get tumours and this occurs most often in does rather than bucks. There is little that can be done for a mouse with a tumour and exhibition breeders normally cull such mice from their breeding program. The most common tumours are mammary tumours in does.

Not all lumps are cancerous however - there are abscesses and benign or fatty lumps as well as minor ailments such as warts that mice can also suffer from.

Ringworm

Ringworm is a contagious fungus that can affect humans as well as many different types of animal. In mice it tends to manifest as thin or missing patches of fur on any area of the body. The skin remains pink and healthy and unbroken. There are creams available from your vet to treat ringworm, but it can be treated just as effectively with over-the-counter products such as athlete's foot cream.

As the fungus spreads easily it can be hard to get rid of, so you may need to treat for a while before you can no longer see symptoms. I have found that tea tree is an effective (and safe) way of treating mice; just dilute with water and spray onto affected animals. If you have a more severe case or would prefer to use a medicated rather than natural remedy, a product called imaverol is available without prescription that is suitable for treating mice. Remember to thoroughly clean all cages before replacing affected mice to remove as much fungus from the environment as possible and avoid recontamination. Always wash your hands after handling mice with ringworm to stop you from contracting it yourself!

Whisker chewing and barbering

PictureBarbered pet doe
As the name suggests, this is the act of a mouse removing the whiskers or fur of one or more of its cagemates. The skin usually remains unbroken and if the victim is removed from the dominant mouse then its hair will regrow.

Scientific studies of this behaviour in mice have concluded that heredity may play a role (National Research Council, 1991). Occasionally there may be two mice in a group that are removing the whiskers from their cagemates; in this case try splitting the group down into pairs to allow you to weed out the culprits.