Feline Calicivirus (FCV)


What is Feline Calicivirus (FCV)?

Feline calicivirus is a very contagious virus seen in cats. It is responsible (along with FVR) for causing upper respiratory infections in cats. This virus is spread through the mucous membranes of the eyes, nose and lining of the eyelids. It can be spread by direct contact, inhalation of sneeze droplets and through sharing of dishes, bedding and litter boxes. This virus mutates readily during replication, meaning that there are many different strains of the virus out there.  Some strains are more pathogenic than others and can cause a more severe case of disease. This virus can remain stable in the environment for up to a month.


What are the symptoms of FCV?

The most common symptoms of FCV are that of an upper respiratory infection. This will include symptoms such as eye and nasal discharge, conjunctivitis and sneezing. More generalized symptoms can include lethargy, loss of appetite and fever.

Feline calicivirus can also cause chronic gingivitis and stomatitis (inflammation seen in the mouth). This can lead to ulcers on the tongue, palate, nose and lips.

Occasionally, the virus will cause inflammation in a cat’s joints. This arthritis can show symptoms for lameness or pain when walking.

The more pathogenic strains that cause a more severe case of disease will create infection within the organs and the cells in blood vessels. This can result in severe disease including pneumonia, hepatitis, pancreatitis, skin ulceration and internal bleeding. These strains are rare, but about half of affected cats will die from this severe infection.


How is Feline Calicivirus diagnosed?

Diagnosing FCV is usually based on the cat’s medical history, vaccination status, clinical signs and physical exam. A specific diagnosis of FCV is usually not necessary. The presence of symptoms of an upper respiratory infection is enough to diagnose a FCV (and/or a FVR) infection. If a specific diagnosis is required, ocular or oral swabs can be submitted to an outside lab where the virus can be cultured or detected by PCR testing.

How is FCV treated and prevented?

Treatment is typically based on the severity of the symptoms. Secondary eye infections are usually treated with topical eye drops. If the secondary infection seems more wide spread, oral antibiotics may also be prescribed. Supplementation with probiotics or lysine may be recommended to help support their immune system. Using a humidifier or placing your cat in the bathroom while you shower can help with congestion and with expelling any mucous in their nose.

It is very important to keep your cat eating. If they are turning away from food, heating it up may be enough to entice them to eat. Cats that go completely off food for an extended period of time may need a feeding tube placed.

Pain associated with any inflammation in the mouth or joints can be managed with pain medication and/or anti-inflammatories.

If the infection is a severe one and the cat has developed pneumonia or other organ inflammation/infection or is suffering from a bleed the cat will need hospitalization for treatment. IV fluids, injectable medications, feeding tube placement and oxygen therapy may be needed to support the cat through the infection.

Vaccination is available against FCV, it is part of the RCP core vaccine given to cats (the “C” in the vaccine name stands for calicivirus). Vaccination will not necessarily prevent cats from contracting FCV, but it does significantly help reduce the severity of clinical disease if the cat does catch the virus. There are also very many strains of this virus, therefore the vaccination has the potential to miss the strain your cat may be exposed to and will not protect them from the disease.


In areas where cats are housed together (catteries, shelters, multi-cat households) vaccination, thorough cleaning of litter boxes and dishes as well as proper general hygiene should be ensured to limit the spread of FCV. Cats infected with an upper respiratory infection should be isolated from the other cats until they make a full recovery. Cats can shed the virus for up to a month post recovery.