Transmission/cause: Hypersensitivity or allergic reaction to mosquito bites.

Affected animals: Mosquito bite hypersensitivity is a clinical entity in cats living in or near mosquito-endemic environments.

Clinical signs: This disease generally presents seasonally with the increased presence of mosquitoes. There is no age or breed predilection, however the majority of affected cats spend are indoor/outdoor cats. Lesions generally occur on non-haired or poorly haired areas such as the bridge of the nose, ear flaps, or pads of the feet. Lesions usually present as small raised nodules (papules), that progress to plaques that often have an erosive or ulcerated, crusted appearance.

Diagnosis: Diagnosis is most often based on clinical presentation and seasonal occurrence, and resolution with avoidance of mosquitoes, however, biopsy with histopathology is very helpful in eliminating other possible diseases with similar presentations, including autoimmune diseases, other hypersensitivity disorders or even dermatophytosis (ringworm).

Treatment: The best option for treatment is avoidance and control of mosquitoes. Ideally, the affected cat should be kept indoors. If this is not possible, keeping the cat inside during dawn and dusk helps to decrease exposure. Mosquito repellents can be applied to the most affected and exposed areas, however cats can be very sensitive to the effects of certain repellent ingredients so it is important to ask your veterinarian which ingredients are safe. For cats that are severely affected, systemic or injectable steroids can be effective to control inflammation and resolve skin lesions.

Prognosis: Good, as this has only seasonal occurrence.