Feline Ocular Herpes
Dr. Noelle La Croix, DVM, DACVO
Understanding Feline Ocular Herpes
The feline herpesvirus (FHV-1) can replicate within the conjunctival epithelia, upper respiratory tract epithelia, and sensory ganglia.
Neuronal infection with FHV-1 establishes lifelong latency with intermittent re-activation and viral shedding. Virus transmission is commonly associated with exposure to acutely infected cats or recrudescing latently infected cats.
Environmental contamination with FHV-1 is not considered a significant route of transmission.
What causes Feline Ocular Herpes?
The feline herpesvirus (FHV-1) is a highly contagious virus that is one of the major causes of upper respiratory infections in cats and kittens. One of the many potential long-term sequela of exposure to this virus is damage to the ocular and periocular tissues. The virus is transmitted via oral, nasal, and conjunctival routes. The primary source of kitten infections is spread from their mothers at birth or during the first few weeks of life. The symptoms of viral upper respiratory infection usually will last for two to three weeks, however latent herpesvirus often remains dormant in the nerves of the face, eyelids, or corneal tissues. Recurrence of clinical symptoms of ocular disease can return periodically throughout life, especially during times of systemic illness or stress. In one study, 70% of cats shed herpesvirus when administered glucocorticoids (steroids).
How is Feline Ocular Herpes diagnosed?
Clinical symptoms and patient history will usually provide a presumptive diagnosis of ocular FHV infection. Specific diagnosis can also be determined with the aid of microscopic examination of the corneal and conjunctival surfaces, special corneal staining tests, and with cytology and culture of ocular surfaces. Symptoms of active infection can include fever, lethargy, sneezing, ocular discharge, nasal discharge, and conjunctivitis. Corneal ulceration can be a complication of infection and when ulceration is present, ocular pain and cloudiness of the corneal tissues is noted. In many young patients, permanent scarring and damage to the conjunctival tissues and cornea can occur. This condition is called symblepharon. Older cats may exhibit evidence of corneal stroma keratitis, eosinophilic keratitis, corneal sequestrum formation, and/or decreased tear film production.
How is Feline Ocular Herpes managed?
There are several goals when discussing therapy for patients with ocular herpes. The initial goal of therapy is to provide supportive care, manage complications from the symptoms, and to try to shorten the duration of clinical signs. Treatment can include oral and topical ophthalmic antiviral medications, oral and topical ophthalmic antibiotics to protect tissues for opportunistic bacterial infections, and supportive systemic care. Owners need to be educated about potential recurrences throughout life and how to manage these flare ups. Topical and oral steroidal products should be avoided as these can further suppress the patient’s nature immunity from helping clear the viral loads. In many situations, supplements for the diet are recommended in order to boost the patient’s immune system.
When chronic ocular symptoms or damage to the ocular tissues are noted, consultation with a veterinary ophthalmologist is strongly recommended. In many cases, damage from the virus can result in the need for ophthalmic surgical or long term ophthalmic medical therapies.
WARNING: GRAPHIC PHOTOS
Figure 1: The right eye of a kitten with symblepharon.
Figure 2: The left eye of a kitten with corneal scarification.