Are Rodent Ulcers in Cats Contagious?

I'm so glad we got rid of that rodent ulcer. It marred my beauty.
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If your cat develops rodent ulcers, it's not because he's somehow been secretly consuming rats or mice. "Rodent ulcer" is just one of several names used to describe feline eosinophilic granuloma complex. It's also known as an indolent ulcer. It's not contagious. The causes of rodent ulcers vary.

Eosinophilic Granuloma Complex

Eosinophilic granuloma complex makes up three separate skin diseases in felines, one of which is the rodent ulcer. According to the Veterinary Partner website, EGC is "an incompletely understood condition," best seen as "an extreme symptom of allergic skin disease." Eosinophils, a kind of white blood cell, function as part of kitty's immune system. When the body signals that parasites or allergens have invaded, eosinophils go on the attack, releasing chemicals to repel the invaders. With allergens, eosinophil activity sometimes backfires, causing rodent ulcers. That name comes from an old belief that these ulcers were caused by viruses cats picked up from eating rats and mice.


A rodent ulcer starts as a spot, generally on kitty's upper lip. Spots might also appear on the lower lip, inside the mouth or on the tongue. It eventually swells and ulcerates, becoming a sore. While unsightly, it causes kitty no pain. Your vet usually makes a diagnosis just by physical examination. Since bartonella bacteria, also known as cat scratch fever, causes similar lesions, your vet should test your cat. If your cat tests positive for bartonella, antibiotics usually clear up the sores.


Rodent ulcers are often the result of kitty's reaction to certain allergens. He might suffer from flea or food allergies, or something in his environment. Some affected cats may have immune disorders or genetic predisposition to these ulcers. If kitty develops these ulcers every spring and fall, it's likely a pollen or mold reaction. You should ask your vet to conduct allergy tests on kitty before actual treatment begins.


Treatment depends upon the cause. In the case of flea allergies, applying a monthly topical flea product might allow the ulcer to heal. If you can pinpoint a food allergy, a change of diet does the trick. Of course, it's not always that simple. Your vet generally prescribes an antibiotic to get rid of any bacterial infection and cortisone or other steroids to clear up the ulcer. You can give your cat over-the-counter fatty acid supplements such as fish or flax seed oil to aid in healing. If the ulcer persists after standard treatments, your vet might consider radiation or cyrosurgery, along with drugs such as cyclosporine.

Always check with your veterinarian before changing your pet’s diet, medication, or physical activity routines. This information is not a substitute for a vet’s opinion.

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