Feline Herpesvirus

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Herpes Virus in Cats

Feline herpesvirus (FHV in cats) is a virus spread among cats that primarily causes herpes upper respiratory infection including ocular or eye disease. While similar to the herpesvirus that affects humans, feline herpesvirus cannot infect humans, nor can human herpes affect cats.

How is the herpes virus in cats transmitted?

Unlike in humans, FHV is not a sexually transmitted disease (STD). Herpes in cats is mostly transmitted through respiratory or eye fluids such as tears, mucus from the nose or eyes, or saliva. Cats do not always show symptoms, so it can be difficult to know whether a cat is contagious or not. FHV does not survive well outside a cat’s body, meaning that the herpes virus does not live long in the environment, so the disease is more of a concern with cats that live closely with each other or cats living in crowded environments (e.g., animal shelters, multi-cat households).

Symptoms of Herpes Virus in Cats

Symptoms of FHV are primarily associated with the upper respiratory tract and eyes. Symptoms of feline herpes upper respiratory infection primarily includes sneezing and a runny nose (nasal discharge), which can range from clear and watery to thick and discolored. Herpesvirus in cat’s eyes can vary but cats frequently have runny eyes (ocular discharge) with discharge that ranges from clear and watery to thick and discolored, as well as swelling at or underneath the eyelids (conjunctivitis). Usually eye and upper respiratory tract symptoms are seen together.

Herpesvirus in cat’s eyes can also cause corneal ulcers, which are infections of the clear layer of the eye (seen over the pupil and iris). Symptoms can include redness of the white part of the eye (sclera), squinting, and an unusual appearance to the cornea such as haziness.

Kittens or cats with other health problems may experience more severe forms of FHV. The herpes virus may reproduce more quickly in these individuals, causing more widespread illness with more intense symptoms. Poor appetite, not wanting to move around, and fever can indicate a more severe infection with FHV.

FHV Symptoms Can Come and Go

For many cats, once they are infected with FHV, they will remain infected for life. Symptoms may appear to wax and wane or come and go, this is known as latency. The herpes virus will hibernate or remain dormant within the cat’s cells until something triggers it to re-activate. Usually triggers are associated with stress on the body such as becoming ill, pregnancy, or something that suppresses the immune system (e.g., steroid use). Emotional stress, such as boarding, new members within the household, or major changes in routine may also trigger FHV into activity.

Can FHV be treated?

No cure exists for FHV. Antibiotics will not treat the herpes virus, but may be used in cases where a secondary bacterial infection is suspected. Medications to help with breathing may also be used. For severe infections, hospitalization may be necessary to provide hydration, IV antibiotics for secondary bacterial infections, or to treat associated symptoms. Treatment for herpesvirus in cat’s eyes will likely include eye drops to control conjunctivitis and/or ulcer symptoms.

Antiviral medications such as L-lysine or famciclovir have been studied in cats with FHV and may be helpful in some cats. More studies are needed to fully understand their use. Do not attempt to start these medications without consulting your veterinarian first.

FHV Vaccines

Several types of vaccines exist for FHV. Most are combined with other vaccines in the same vial (e.g., “5-in-1 vaccine”). These vaccines do not result in 100% protection from contracting herpes, but they do significantly decrease symptoms and contagiousness. The American Association of Feline Practitioners (AAFP) recommends vaccinating cats against feline herpesvirus at 9 weeks of age, 12 weeks of age, and then at 15-16 weeks of age. A booster is recommended at one year of age with additional boosters recommended at least every three years after the one-year booster.