A rodent ulcer begins as a yellow or
pink shiny spot that deepens and becomes an open sore. Often, it begins on
either side of center on the upper lip. Less commonly, it occurs on the lower
lip or at the back of the jaw behind one of the last upper molars. Some cats
will also develop an ulcer on the tongue. It is not itchy and seems to cause no
pain. As the ulcer advances, the lip may be partly eroded by a large, ulcerated
swelling that exposes teeth and gums.
This unsightly condition is unique to the cat. It may be found in cats of
any age, and occurs three times more often in females than males. The exact
cause of rodent ulcer is unknown, and there is actually no direct connection
with rodents. The presence of eosinophils suggests an allergic reaction,
parasite problem, or immune problem. It is thought to be part of the
eosinophilic granuloma complex. Hypersensitivity is strongly suggested, with
causative agents including insects, environmental substances, and diet. Flea allergy should always be
considered as a possible cause. Some cases are associated with dental
infection. An underlying genetic predisposition is suspected.
Toxoplasmosis is a disease caused by the parasite Toxoplasma gondii, which can be found in garden soil and raw meat. Cats can get toxoplasma infection by killing and eating infected prey. The disease can also be passed on from cats to humans.
Rodent ulcers have been found in cats who were exposed to the feline leukemia virus, further
suggesting that impaired immunity may be a cause. However, not all cats with
rodent ulcer test positive for the feline leukemia virus, nor does a rodent
ulcer necessarily mean that a cat has feline leukemia.
Diagnosis is suggested by the typical appearance and location of the ulcer.
In questionable cases, a biopsy or needle aspirate cytology can be done to rule
out malignant transformation. Cats with rodent ulcer should be tested for
Treatment: Veterinary care is required in all cases. Cortisone has proven to
be the most effective treatment, but it should be given with an antibiotic, at
least initially, to clear up any secondary bacterial infection. Cortisone is
given either as pills (prednisone) or by injection (Depo-medrol). Depo-medrol
is a long-lasting injection that is given at two-week intervals. Usually, three
courses are necessary. Alternately, prednisone can be given daily until the
ulcer disappears. If the ulcer recurs after either injectable or oral cortisone
therapy, the cat is placed on prednisone maintenance-usually one pill every
other day. Essential fatty acid supplements may also be beneficial.
In case this is the result of an allergen or irritant, do not use plastic or
rubber food and water bowls. Stainless steel is a good alternative.
Cyclosporine, interferon, radiation therapy, and cryosurgery may all be
effective. Gold salts, given as an injection, may also be used for treatment in
cases that are difficult to treat.
Megestrol acetate (Megace) has been used in some cases of rodent ulcer.
However, this progesterone drug is not approved for cats and has serious
undesirable side effects. It is best used as a last line of treatment under
veterinary supervision. These ulcers are known to recur, so it is worthwhile to
try to find and eliminate the underlying cause.
WebMD Veterinary Reference from "Cat Owner's Home Veterinary Handbook"