EOSINOPHILIC KERATOCONJUNCTIVITIS IN A HORSE

An 11-year-old Quarter Horse gelding was evaluated because of a persis tent, raised band of 1- to 2-mm subepithelial plaques of the left corn eal Cytologic examination of corneal scrapings revealed numerous eosin ophils and segmented neutrophils, with few mast cells, plasma cells, a nd lymphocytes. Bacteriologic culture yielded sparse growth of alpha-h emolytic Streptococcus and Staphylococcus spp. Histologically, the pla ques consisted of subepithelial foci of fragmented and degenerated col lagen fibers infiltrated by eosinophils and neutrophils, with few lymp hocytes, plasma cells, and macrophages. Plaques were surrounded by a l ayer of brightly eosinophilic, acellular, granular material. Distribut ion of inflammatory cells in the conjunctiva was similar to cells in t he cornea. After reepithelialization of the cornea, corticosteroid oin tment was administered topically. Twenty-eight days after treatment wi th corticosteroids, the plaques had completely resolved. Histologic an d cytologic diagnoses in this horse were similar to reports of eosinop hilic keratitis in cats.