Feline Herpesvirus 1 (FHV-1) Infection

What Is Feline Herpesvirus 1 (FHV-1) Infection?

In cats, the feline herpesvirus-1 (FHV-1) is a virus affecting primarily the upper respiratory tract and the structures of the eye. Transmission occurs between cats by direct contact with infected oral, nasal, or eye secretions. Within 24 hours, a newly infected cat can transmit the feline herpes virus to other cats, so it’s important to seek veterinary care immediately.  

FHV-1 is the most common viral cause of sneezing and nasal discharge in cats. Changes to the structures of the eye are also associated with feline herpes infection. 

Young cats are most affected, but infection can occur at any age. Cats from multi-cat households, shelters, rescues, and catteries are at increased risk for infection. Outdoor, stray, and feral cats may become infected from contact with infected cats while outside. 

Symptoms of Feline Herpesvirus 1 (FHV-1) Infection

Clinical signs can vary in severity. Upper respiratory signs include: 

• Sneezing 

• Nasal discharge  

• Fever 

• Loss of appetite 

• Coughing 

Changes to the eye may include: 

• Eye discharge 

• Conjunctivitis (pink eye) or chemosis (enlargement of the pink lining of the eye) 

• Changes in the color of the eye 

• Corneal ulcer (scratches or tears of the clear part of the eye) 

In severe cases, changes to the skin around the face may include: 

• Redness 

• Swelling 

• Crusting 

• Loss of hair 

Causes of Feline Herpesvirus 1 (FHV-1) Infection

The feline herpes virus attacks the lining of the nose, tonsils, conjunctiva (lining of the eye), and cornea (visible part of the eyeball). As the virus continues to replicate (make copies of itself), it may be spread through secretions or close direct contact. If not treated early, the virus can infiltrate the bones associated with the nose and mouth, causing long-term physical damage.

How Veterinarians Diagnose Feline Herpesvirus 1 (FHV-1) Infection

The most sensitive test for feline herpes virus is a PCR test, which is conducted on swabs from deep in the mouth, the eye, or on biopsies from the skin. This test, however, does not differentiate between the active form of infection and a chronic carrier state.

A positive result could mean the pet was infected from another sick cat and is now a carrier of the virus, the pet has been vaccinated for feline herpes, or the pet is showing signs from an active infection of feline herpes. Therefore, a diagnosis is usually made based on the physical exam, symptoms, and the pet's history.

Treatment of Feline Herpesvirus 1 (FHV-1) Infection

Treatment depends on the severity of disease, vaccine status, age, and underlying health conditions.  

Currently, there are no specific medications for the herpes virus in cats; however, in severe cases, human antiviral medications, like Famciclovir, can help. Famciclovir may reduce clinical signs and decrease the virus shedding in the secretions of infected cats. For pets with symptoms affecting the eye, topical eye medications may be used. 

Supportive care is the foundation of treating pets affected by the feline herpes virus. Supportive care is aimed at decreasing more severe symptoms like pneumonia and physical damage to the nose and eye structures. Traditionally, the virus is active for 7 to 10 days, so in mild cases, pets may require no treatment as symptoms improve.  

Supportive care can include fluids for hydration and routine cleaning of the nostrils and eyes (if they are affected). Also, lysine immune supplements decrease the virus’s ability to replicate. These supplements are available as a powder, paste, or treat. Probiotics with Enterococcus faecium SF68 support the immune system.  

In severe cases, a cat may need to be stabilized in the hospital before supportive care can be started at home. 

Since antibiotics work against bacteria, they are not used in every case of infection with the feline herpes virus. If a secondary bacterial infection is present, antibiotics are used to fight that infection while the virus runs its course. 

Recovery and Management of Feline Herpesvirus 1 (FHV-1) Infection

When caught early, most cats with symptoms due to the herpes virus will recover in 10-14 days with supportive care. Death may occur with severe disease symptoms, especially in kittens and cats that are immunosuppressed. 

In severe cases, or when cats are affected when very young, physical damage to the bony structures of the face can occur, causing deformities and scarring. That physical damage predisposes affected cats to further complications like pneumonia, chronic nasal disease, and recurrent flares of infection. 

Prevention of FHV-1 

• Isolation of sick cats: Separate cats showing signs of an upper respiratory disease, or those with abnormal eye discharge, from other cats. When separated, allow your affected pet to have use of an individual water bowl, food bowl, litter box, toys, and bedding. 

• Clean shared spaces and items: FHV-1 is very susceptible to disinfectants. The feline herpes virus survives only 18 hours outside of the host. It is easily inactivated by bleach. 

• Reduce stressors: Provide cats that are housed together enough space to drink and eat and use a litter box without crowding or aggression. Maintain a normal routine of deworming, enrichment, and rest. Adding pheromone therapy (like Feliway) reduces stress for cats. 

• Vaccinate: There is a vaccine to decrease the symptoms associated with herpes virus infection in cats. This combination vaccine protects against feline herpes, feline calicivirus, and feline panleukopenia (feline distemper). Starting at 6-9 weeks of age, cats can receive their first combination vaccine. Booster vaccines are required every 3-4 weeks until 16 weeks of age. For appropriate protection, this requires at least two vaccines. If the booster vaccine is not given within the appropriate window, cats are not properly protected and are at risk for developing symptoms. Cats are considered protected two to three weeks after their last vaccine in the series.  

It is possible for vaccinated cats to become infected with the feline herpes virus and become chronic carriers. But when vaccinated, those cats develop milder symptoms and shed less of the virus for a shorter amount of time compared to unvaccinated cats.