Experimental Canine Herpesvirus-1 Primary Ocular Infection in Adult Dogs

Abstract

Purpose: : To establish the ocular pathogenic potential of canine herpesvirus-1 (CHV-1) in adult dogs and to characterize clinical ocular disease, viral shedding, and serologic response of primary CHV-1 ocular infection.

Methods: : Eight 1.5 year old specific pathogen-free (CHV-1 free) beagles were inoculated in the right eye with 2x10⁵ TCIM₅₀ of CHV-1 by corneal microtrephination (n = 4 dogs) or conjunctival drop (n = 4) methods. Forty-eight hours prior to inoculation, 4 of the dogs (2 from each inoculation method group) received 10 mg of methylprednisolone acetate subconjunctivally in the right eye. Following inoculation, physical and slit-lamp biomicroscopic examinations were performed daily for the first 21 days post-infection (PI) and every-other-day for the following 14 days. Conjunctival swabs for real-time quantitative CHV-1 PCR and virus isolation were collected from both eyes for 35 days PI. Buffy coats were collected for CHV-1 PCR for 35 days PI. Serum for CHV-1 serum neutralization (SN) titers was collected for 119 days PI.

Results: : All dogs developed bilateral, mild-to-moderate conjunctivitis that reached maximal intensity 7-10 days PI and resolved over the subsequent 21 days. Ocular viral shedding was present from the right eye of all dogs and the left eye of 2 dogs between 3 and 10 days PI. All dogs developed CHV-1 SN titers, beginning on day 7 PI, peaking on day 21 PI, and declining over the subsequent weeks. All buffy coat CHV-1 PCR assays were negative. No dogs developed clinical systemic disease. Following recovery from primary infection, all dogs remained subclinical, did not shed virus, and had stable or declining CHV-1 SN titers.

Conclusions: : Canine herpesvirus-1 primary ocular infection in adult dogs is associated with self-limiting conjunctivitis and ocular viral shedding, which occurs in the absence of clinically detectable keratitis or systemic disease. The relative magnitude of ocular lesions associated with experimental primary CHV-1 ocular infection in adult dogs is mild and the duration of viral shedding is short, in contrast to experimental alphaherpesvirus primary ocular infections in many other animal species.

Keywords: conjunctivitis • microbial pathogenesis: experimental studies • herpes simplex virus