Mosquito Bite Hypersensitivity in Cats
Veterinary & Aquatic Services Department, Drs. Foster & Smith

Picture of a mosquito

Mosquito bite hypersensitivity is a relatively common disease in cats that occurs during the summer months in warm climates. Mosquito bite hypersensitivity was first described in the 1980's.

What is mosquito bite hypersensitivity?

Mosquito bite hypersensitivity is an overreaction of the cat's immune system to a mosquito bite. The immune system is the body's defense mechanism and when something foreign is encountered, like mosquito saliva, the immune system tries to get rid of it. In the case of hypersensitivity, the immune system basically does not know when to quit and causes a more severe problem than the mosquito bite itself.

What does mosquito bite hypersensitivity look like in a cat?

The most typical lesions are areas of crusts, scaling, and raw ulcers. These lesions most commonly occur on the ears and nose. Long-term, cats may develop hair loss and pigment changes in the affected area. In many cases the pads of the feet will be thickened, swollen, tender, and red, and may have fissures. Some cats will have a slight fever and swollen lymph nodes.

How is mosquito bite hypersensitivity diagnosed?

Mosquito bite hypersensitivity can look like many other skin problems in cats including ringworm, food allergy, eosinophilic plaque, lupus erythematosus, squamous cell carcinoma (a cancer) and bacterial infections. The diagnosis of mosquito bite hypersensitivity is based on the signs of disease, season of the year, biopsy results, and improvement of the lesions when the cat is confined in a mosquito-free area for 4 to 7 days.

How is mosquito bite hypersensitivity treated?

Mild cases will resolve on their own if the cat is isolated from mosquitoes. More severe mosquito bite hypersensitivity is treated with corticosteroids either by injection or orally.

How is mosquito bite hypersensitivity prevented?

Prevention is based on limiting exposure to mosquitoes.

Mosquito control is extremely important. Keeping cats indoors is very helpful, especially during the times of the day when mosquitoes are most active - dawn and dusk. Some cats with a known hypersensitivity are treated with lower doses of steroids intermittently through the mosquito season. Insect repellents which contain pyrethrin can be used.

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