Equine Insect Bite Hypersensitivity and its Therapeutic Management

Insect bite hypersensitivity is an IgE-mediated allergic dermatitis of horses caused by bites of insects such as Culicoides, Simulium spp., Stomoxis calcitrance. The cause of hypersensitivity is the allergen proteins of salivary gland from these insects. Three horses (two female and one male) of two to five years of age presented to Teaching Veterinary Clinical Complex of College of Veterinary and Animal Science, RAJUVAS, Bikaner with the history of sudden onset of generalized itching or in two cases, while one horse have history of itching since three days back. The main clinical signs observed were hives, itching, hair loss, scaling and crusting, and eventually whitening of hairs and thickening of skin in the affected areas of the neck, shoulders, ears, face and belly. The physiological parameters such as temperature, pulse rate and respiration rate were unremarkable. The disease is diagnosed on the basis of history (manifestations of mosquitoes and flies), clinical signs and tests such as skin scrapings, hematology and cultures that rule out other conditions like parasites, fungus and bacteria. All the hematological parameters were normal except rising percentage of eosinophills. The horses received dexamethasone at the rate 0.1 mg/kg body weight and pheneramine maleate at the rate 5 to 10 ml as a single dose in each horse for five days. Additionally fly repellent was also advised to control numbers of mosquitoes and flies along with minimizing dust in the barn by changing the type of bedding and improving house ventilation. After seven days of treatment, all the horse recovered completely.