Feline Herpesvirus

Herpesvirus is one of the most common causes for conjunctivitis and corneal ulceration in cats. The ocular (eye) symptoms can be accompanied by upper respiratory disease as well. This virus is extremely widespread in the cat population with some studies showing that 90% of cats are exposed to herpesvirus. The virus is not contagious to people or other species (ex: dogs). The virus is passed to other cats through sneezing, coughing, grooming, and generally being in close contact with an infected cat. Routine vaccination by your primary care veterinarian typically includes a herpes virus vaccine. This vaccine will minimize clinical signs of the disease but will not completely protect your cat from infection or future recurrence of herpesvirus.

Symptoms

Herpes virus can cause a range of symptoms in the cat population. The mildest of infections lead to conjunctivitis (redness and swelling in the white part of the eye). Other symptoms include ocular and nasal discharge, sneezing, coughing, and corneal ulceration. Herpesvirus causes superficial or surface ulcers on the cornea (clear windshield to the eye). Secondary bacterial infections, however, can lead to deeper ulcers and even corneal perforation.

Side effects of herpes viral infections include dry eye, symblepharon (permanent attachment of the conjunctiva to the cornea), corneal sequestrum (black plaque on the cornea), tear duct stricture, and corneal scarring.

Studies show that 80% of cats initially infected with the virus will remain infected long-term. These cats are carriers for herpesvirus and will appear clinically normal after the initial infection. The virus lives in the nerves of the face and can cause recurrence of symptoms throughout life. These recurrences typically occur during times of stress or illness. Not all cats will experience recurrence of clinical disease.

Diagnosis

Diagnosis of feline herpesvirus is largely based on ophthalmic examination and response to treatment. Laboratory testing is available; however, tests tend to have many false positives and false negatives.

Treatment

Your ophthalmologist will likely prescribe anti-viral medications to aid in controlling the symptoms of herpesvirus. Anti-viral medications slow replication of the virus and allow your cat’s immune system to resolve the infection. These medications will shorten the time period during which your cat is showing signs of herpesvirus infection. The medication will not completely clear herpesvirus from your cat's system.

As viruses predispose animals to secondary bacterial infections, your cat may be placed on an antibiotic to protect against these infections.

Studies have shown that during active herpesvirus infection, the tear film is negatively affected in cats. Thus, topical artificial tear preparations or other lubricants may be prescribed.

Lysine, an amino acid supplement, has been shown to increase the time period between recurrences of herpesvirus symptoms. There are many formulations of lysine and your veterinary ophthalmologist will discuss which might be best for your cat.

As herpesvirus creates quite a bit of inflammation it may be tempting to treat cats with oral or topical steroids. This unfortunately will slow the cat’s immune response to the virus. Thus, the virus may cause more damage to the eye or the infection may last much longer than usual and become difficult to control. Topical and oral steroids are contraindicated in the treatment of feline herpesvirus.