Ulcerative Keratitis Associated With Naturally–occurring Canine Herpes Virus Infection in Two Dogs

Abstract

Abstract: : Purpose: To describe two canine cases of naturally–occurring ulcerative keratitis associated with canine herpes virus corneal infection. Methods:Both dogs were presented for evaluation of blepharospasm and epiphora. An eight–year–old Labrador Retriever with well–regulated diabetes mellitus underwent bilateral phacoemulsification 2–weeks prior to presentation and was being treated topically with neomycin–polymyxin–dexamethasone ointment. A seven–year–old Miniature Schnauzer with chronic immune–mediated thrombocytopenia and chronic keratoconjunctivitis sicca was being treated with immunosuppressive doses of oral prednisone and topical 0.2% cyclosporine ointment. The first dog was affected unilaterally and the second dog bilaterally. Both dogs displayed multiple, linear, superficial corneal ulcers. The ulcers were highly irregular, with a dendritic–branching pattern. The ulcers healed and did not reoccur in 7 and 4 weeks, respectively, following discontinuation of the topical dexamethasone or cyclosporine ointment and treatment with topical antivirals. Results:Canine herpes virus was isolated from corneal swabs from both dogs on presentation and repeatedly during recheck examinations until the ulcerations were healed. Canine herpes virus serum neutralization titers were markedly elevated in both dogs. Virus isolations from oropharyngeal and genital swabs were negative for both dogs. Aerobic bacterial cultures of the ulcers and corneal cytology were unremarkable. The isolated virus was identified as canine herpes virus by immunofluorescence, electron microscopy, and polymerase chain reaction. Conclusions: These two dogs are the first documented cases of naturally–occurring canine herpes virus ulcerative keratitis. As in other species, local and systemic immunosuppression may be important in the pathogenesis of canine herpetic ulcerative keratitis. Resolution of clinical signs occurred only after the topical immunosuppressive medications were discontinued. The virus isolated was positively identified as a canine herpes virus and displayed a similar morphology and antigenicity to canine herpes virus isolates from puppies with fatal, systemic infections; however, a virus strain with specific corneal virulence cannot be ruled–out.

Keywords: herpes simplex virus • keratitis • cornea: clinical science