Feline herpes virus may be involved with 90% of upper respiratory infections (URI’s) in cats.  The disease is rarely life threatening but is extremely prevalent.  The most common signs of feline herpes are sneezing, loss of appetite, and conjunctivitis (inflammation of the tissues around the eyeball). Most affected cats show mild symptoms that last about two weeks.

Cats that are in stressful environments or that have weak immune systems are more susceptible to the virus.  They are more likely to be sicker when infected, and they are more likely to have chronic problems with herpes.  Unfortunately herpes infection is widespread in animal shelters and is common in cats coming from catteries.  Concurrent diseases and poor nutrition complicate herpes infections and prolong the recovery.  Genetics also play a role in susceptibility and severity of signs.

Viral transmission occurs though sneezing and is spread through the air, by direct contact with infected cats, and by touching contaminated objects.  Humans that do not wash their hands between handling sick cats can inadvertently transmit the virus to other cats.  The virus invades the mucous membranes of the nose, throat, sinuses, and eyes.

Severe infections are found more often in young kittens.  They develop fevers and so much congestion that they cannot smell and do not want to eat.

About 80% of infected cats carry the herpes in their systems for the rest of their lives and this is called a latent infection.  Chronic carriers of feline herpes have a recurrence of signs when they are stressed.  Stresses in these cats could be moving, boarding, surgery, other pets in the household, or anything that changes the home environment. The most common recurrent signs are intermittent bouts of sneezing, clear discharge, and conjunctivitis.

Feline herpes virus (FHV-1), also called rhinotracheitis, does not cause disease in humans.  Humans can be infected with Herpes simplex, which causes fever blisters, and Herpes zoster, which is responsible for chicken pox and shingles.  Many cats that had herpes infections as kittens will have runny eyes for the rest of their lives.  The virus can damage the nasolacrimal ducts, so tears do not drain properly.  Keeping eyes wiped clean daily in these cats is usually the only treatment needed.  Other cats develop a nasal whistle due to permanent damage to structures in their nasal passages by the virus.

The most common form of vaccination against herpes is by injection, but there is also an intranasal (topical) vaccine for this virus.  The benefits of topical vaccination are that it stimulates a more rapid protection and there is no chance of developing an injection site reaction.  The disadvantages of topical vaccination are that they can trigger low grade but temporary sneezing, coughing, and conjunctivitis.  Vaccination against herpes does not prevent infection but does reduce the severity of associated clinical signs.

Diagnosing herpes is usually based on the clinical signs because there are no easy or cheap tests to confirm the disease.  Scrapings from the conjunctiva can be examined by a lab for characteristic changes to the cells.  Swabs of oral or ocular secretions can be sent to a lab for a PCR test or immunofluorescent test for herpes.  The labs can run a panel of PCR tests on swabs to look for other bacterial and viral causes of upper respiratory infection.  It usually takes 3-7 days to get results on these types of tests.

Treatment for herpes is all based on supportive care.  There is no cure for herpes and there is not any specific treatment for this virus.  Cats with mild signs that are still eating and drinking may not need any care.  Cats that are feverish and/or not eating may need fluids, nutritional support, antihistamines, appetite stimulants, nose drops, nebulization, immunostimulants, and supplements.  If there is colored ocular or nasal discharge antibiotics are added to treat secondary bacterial infections.

L-lysine is an amino acid nutritional supplement that is purported to help control herpes infections.  Cats can take 250-500 mg twice daily.  This product is available as easy to dose veterinary preparations (gel, chews, and powder) and in human drug and health food stores as large tablets or capsules.  L-lysine competes with another amino acid called arginine that herpes requires to be active.

My own cat, Keiki, who is now 14 years old, had herpes conjunctivitis when she was a kitten.  She had some recurrent bouts with draining eyes for her first two years of life but then never had any more signs.

If you acquire a cat that has herpes, be patient and stick with your veterinarian’s recommended treatment.  If you have a herpes carrier and want to prevent a recurrence of signs, minimize stress in your household by keeping things clean, providing good ventilation, and avoiding conflict and crowding with too many cats.

Written by Dr. Wexler-Mitchell of The Cat Care Clinic in Orange, CA
Copyright © 2011 The Cat Care Clinic