Mice and rats: miscellaneous health problems

Two medical conditions of mice and rats demanding special mention are their susceptibility to tumours and Tyzzer’s disease. These are covered in separate factsheets. However, there are other medical conditions affecting mice and rats that are briefly covered here. Only purchase rodents from reputable sources, and never purchase an obviously or even suspiciously ill rodent. It is never wise to purchase an animal that has been in contact with one that seems ill, even if the intended purchase appears perfectly healthy. Strict quarantine or isolation of all newly acquired rodents for at least 4 weeks greatly helps prevent disease among pet mice and rats. This recommendation is especially important for pet rodents because of the severity of certain diseases that they may harbor without showing signs of illness.

The tendency to become overweight (often grossly overweight) is more often a problem of pet rats than mice. Overindulgent pet owners and the provision of diets rich in seeds and nuts are most often responsible for this condition.

Owners of pet rats must resist the temptation to feed “junk food,” such as French fries, doughnuts, cookies and candy. Commercial diets specifically designed for rats are always preferred and can be supplemented with whole-wheat bread, dry cereal, pasta, fruits, vegetables and non-fat yogurt.

The incisor (front, gnawing) teeth of all rodents and rabbits grow continuously for the life of the individual. The continual wear between the uppers and lowers usually prevents overgrowth of the teeth. Hereditary abnormalities of the jaw bones and/or teeth, abscessation of the incisor teeth, or injury to he jaw may result in malocclusion (improper meeting of the upper and lower incisors).

Malocclusion, in turn, results in overgrowth of one or more of the incisors, with subsequent injury to the mouth. Mice and rats with this problem must have their overgrown incisors trimmed periodically by an experienced vet or vet technician.

Rat owners, at some point, notice red-brown tears staining the eyelids, nose and sometimes the front paws of their pet rats. This substance is always mistaken for blood, but don’t panic, it isn’t!

It is actually a normal secretion from a large gland behind the eyes. Red-brown tears are noted most often in response to stressful situations such as restraint, fright, illness, etc.

Female rats (mice much less often) disturbed shortly after giving birth to a litter may destroy the pups and eat them. Male rats also engage in the same behaviour. For these reasons, it is important not to disturb female rodents for 2-3 days after they have given birth. Male rats must be removed from enclosures just before the females are due to deliver their litters to prevent this from happening.