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Insect Bite Dermatitis in Dogs, Cats, Horses, and Rabbits

By

Sandra Diaz

, DVM, MS, DACVD, The Ohio State University

Last full review/revision Aug 2021 | Content last modified Aug 2021

Insect bite dermatitis is a worldwide problem caused by inflammatory mediators or toxic substances present in the saliva of various hematophagous insects. It typically affects dogs, cats, and horses. Clinical signs are characterized by small papules and wheals with central hemorrhagic crusts that can progress to multiple small ulcers. Lesions are found on the apexes of the pinnae of cats and dogs with erect ears or on the folded surfaces of the pinnae of dogs with flopped ears. The causative insect can vary with the season and environment and include, among others, mosquitoes Mosquitoes Mosquitoes are members of the family Culicidae. Important genera include Aedes, Anopheles, Culex, Culiseta, and Psorophora. Although they are tiny, fragile dipterans, mosquitoes are perhaps... read more (Aedes spp, Culex spp), the stable fly Stable Flies The stable fly, Stomoxys calcitrans, is often called the biting house fly. It is about the same in size and general appearance as Musca domestica, the house fly. It is brownish gray, the outer... read more (Stomoxys calcitrans), and black flies Black Flies Members of the family Simulidae are commonly called black flies (although their coloration may vary from black to gray to yellow to olive) or buffalo gnats (because their thorax is humped over... read more (Simulium spp). Mosquitoes can also cause a hypersensitivity reaction in cats Environmental-induced (eg, house dust, house dust mites, pollens of trees, grasses and weeds, molds) or food-induced atopic dermatitis is a common allergic disorder of dogs and cats and frequently... read more , characterized by inflammatory lesions on the pinnae, face, and paws.

In horses, bites of the stable fly, black flies, and Culicoides spp Biting Midges Culicoides sensitivity in a horse. The biting midges, “no-see-ums,” or punkies belong to the family Ceratopogonidae. The most common biting midges are Culicoides spp. They are associated with... read more Biting Midges can cause a hypersensitivity reaction or severe dermatitis that results in lesions on the dorsal and/or ventral trunk and face in addition to the pinna. Treatment includes fly repellents, controlling the fly population with environmental clean up (manure, compost, etc), and insecticides. Topical or oral short-acting glucocorticoids may be necessary to reduce the inflammation and pruritus in severe cases. Therapeutic face masks with ears can be use to decrease insect exposure.

The rabbit flea (Spilopsyllus cuniculi), found mainly in Europe and Australia, can affect dogs and cats, and it adheres tightly to the skin of the tip and edges of the pinna, where it may cause dermatitis. The rabbit flea is an important vector of diseases, including myxomatosis,

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