Feline herpesvirus type 1 (FHV-1) establishes lifelong latency in cats after primary infection, causing recurrent upper respiratory and ocular disease triggered by stress. Understanding its management is essential for the welfare of the millions of cats that carry this virus.
Latency and Reactivation
After primary infection, FHV-1 travels to sensory ganglia (particularly trigeminal ganglia) where it remains in a latent state. Reactivation — triggered by corticosteroid administration, concurrent illness, rehoming, introduction of new animals, or other stressors — causes viral replication and clinical recurrence. Reactivating cats shed virus and can infect susceptible cats, making stress management important in multi-cat households.
Ocular Manifestations
FHV-1 causes some of the most challenging feline ocular conditions:
- Conjunctivitis — recurring or chronic conjunctival inflammation with discharge
- Corneal ulceration — dendritic (branching) ulcers are pathognomonic for FHV-1; superficial ulcers usually heal well but stromal ulcers may progress
- Corneal sequestrum — dark, necrotic plaque of corneal tissue; more common in Persians and Himalayans; requires surgical removal
- Eosinophilic keratitis — chronic inflammatory condition associated with FHV-1
- Symblepharon — adhesions between conjunctiva and cornea; result of severe primary infection in kittens
Management Strategies
Antiviral therapy: Famciclovir (40mg/kg orally 3×/day) is the most evidence-supported systemic antiviral in cats. Topical antivirals (idoxuridine, cidofovir 0.5% drops) are used for ocular disease. Treatment during reactivation episodes reduces severity and duration.
Lysine: Historically recommended to compete with arginine (required for FHV-1 replication); meta-analyses show inconsistent evidence but widely used at 250–500mg/day.
Stress management: FELIWAY Classic diffusers, maintaining stable routines, avoiding unnecessary household changes, and gentle introduction of new animals reduce reactivation frequency.
Interferon: Feline interferon omega (Virbagen Omega) has some evidence for reducing FHV-1 severity when applied topically or given systemically.
Welfare Considerations
Cats with recurrent FHV-1 disease experience chronic ocular discomfort — squinting, discharge, and photophobia signal active disease requiring treatment. Regular veterinary monitoring of ocular health, prompt treatment of ulcers (which can perforate if neglected), and effective stress reduction management are the pillars of good welfare for FHV-1 carrier cats.