Calicivirus in Cats. Symptoms and Treatment Options

What is Calicivirus?

Feline calicivirus is a highly contagious virus that commonly causes upper respiratory infections in cats [1]. The virus attacks the oral cavity and upper respiratory tract, leading to symptoms such as sneezing, nasal discharge, sores on the tongue, ulcers in the mouth, and conjunctivitis. Calicivirus spreads through direct contact with infected saliva, nasal secretions, or contaminated surfaces. It is very easy for the virus to spread between cats in multi-cat households or shelters. Kittens and cats with weaker immune systems tend to experience more severe symptoms. Typical symptoms of calicivirus infection include sneezing, eye discharge, drooling, loss of appetite, lethargy, fever, and limping or lameness in some cases.

Diagnosing Calicivirus

Diagnosing calicivirus in cats begins with a physical exam by a veterinarian. The vet will look for typical signs of infection like oral ulcers, nasal discharge, conjunctivitis, and fever. They may also feel for enlarged lymph nodes which can indicate infection.

To confirm diagnosis, the vet can collect samples from the mouth, nose, or eyes and analyze them for presence of the virus. There are two main testing methods:

  • Virus isolation – growing the virus in cells in a petri dish. This detects active virus shedding.
  • PCR (polymerase chain reaction) test – detects viral DNA in samples. This is very sensitive and can identify cats infected even if not shedding virus. (VCA Animal Hospitals)

Other diagnostic tests like bloodwork may also be recommended to assess overall health and rule out other conditions. Quick and accurate diagnosis allows vets to provide appropriate treatment for calicivirus infection.

Treatment Options

There is no direct cure for calicivirus, so treatment is focused on providing supportive care to ease symptoms while the cat’s immune system fights the infection ( Treatment options include:

Supportive care: This involves keeping the cat hydrated by giving fluids under the skin or intravenously. Appetite stimulants may help a cat who has gone off their food. Vitamin supplements can support the immune system. Providing soft foods makes eating easier for cats with painful mouths. Keeping the eyes and nose clear of discharge aids breathing and vision.

Antiviral medications: Antiviral drugs like famciclovir may be prescribed, but these only help control signs rather than curing the infection. Pain relievers are often given as well to reduce discomfort (

Pain management: Pain medication like buprenorphine helps with the discomfort caused by mouth ulcers and fever. Anti-inflammatories can reduce swelling and tenderness. Appetite stimulants are also useful for cats who have gone off their food due to sore mouths.

At-home Care

Cats diagnosed with calicivirus can often be treated at home as long as they are eating, drinking, and otherwise behaving normally. Isolation is important to prevent spreading the infection to other pets. The sick cat should be confined to one room and have its own litter box, food bowls, water bowls, and bedding.

Make sure the cat is eating enough to maintain its weight and energy levels. Offer smelly, fish-flavored foods or canned kitten foods which are more palatable for cats with decreased appetite. Handfeeding small frequent meals may help. Adding warm water to dry or canned food can increase palatability.

Hydration is critical, especially if the cat has mouth ulcers making eating painful. Provide fresh water bowls around the house. Adding tuna juice, low-sodium chicken broth, or flavored electrolytes can encourage drinking. Subcutaneous fluids administered under the skin may be necessary if the cat is not drinking enough on its own.

According to Feline Calicivirus from Cornell University’s Baker Institute, severely affected cats may need more intensive nursing care with IV fluids, feeding tubes, and other supportive care. Consult your veterinarian if home care does not seem to be improving the cat’s condition.


Preventing calicivirus infection in cats focuses on vaccination, sanitation, and limiting exposure. Vaccination is the first line of defense against calicivirus. Kittens should receive a series of vaccines starting at 6-8 weeks of age, with boosters every 3-4 weeks until 16 weeks old. Adult cats need annual vaccination boosters to maintain immunity. While the vaccine may not fully prevent infection, it can reduce viral shedding and illness severity.

To limit viral transmission, thoroughly disinfect any objects, surfaces, food/water bowls, litter boxes, or bedding that may have come in contact with an infected cat’s saliva, nasal discharge, or feces. Use a dilute bleach solution (1 part bleach to 32 parts water) and allow a 10-15 minute contact time. Restrict interactions between infected and healthy cats.

Since calicivirus is extremely contagious between cats, limiting exposure is key. Keep cats indoors and isolated from any potentially infected cats, especially in high-risk settings like shelters. Avoid bringing new cats into a household without proper quarantine. Disinfect all objects before allowing contact between existing and new cats.


The prognosis for cats with calicivirus is generally good, as the infection is usually self-limiting. In most cases, cats will recover within 1-2 weeks with supportive care at home [1]. However, there are some potential complications to be aware of.

In rare cases, calicivirus can cause severe oral ulcers, pneumonia, limping, and chronic stomatitis (severe inflammation of the mouth). The virulent systemic strain has up to a 67% mortality rate [2]. Kittens, senior cats, and immunocompromised cats tend to be more severely affected.

With prompt veterinary care and at-home supportive care, most cats fully recover from calicivirus. However, the virus remains dormant in the body and cats can suffer recurrences throughout their lifetime, especially during periods of stress. While recurrences are usually mild, owners should monitor their cats closely for any return of symptoms.


Calicivirus is highly contagious and spreads easily from infected cats to other cats. The primary route of transmission is through direct contact with the saliva, nasal mucus, or eye discharge of an infected cat. When an infected cat sneezes or coughs, it releases aerosol droplets containing the virus into the air. If another cat inhales these droplets or comes into contact with contaminated surfaces, they can become infected.

According to the Cornell Feline Health Center, “the virus spreads through direct contact with the saliva, nasal mucus and eye discharge of infected cats and through aerosol droplets that spread when cats sneeze.”

Cats in high density populations like shelters are especially susceptible as the virus can quickly spread between cats sharing space and litter boxes. Even household cats are at high risk if one cat becomes infected. Owners should isolate sick cats and disinfect any shared items like food bowls to prevent household spread.

Risk Factors

Certain cats are at higher risk of contracting calicivirus. According to research from Cornell University, unvaccinated cats are more likely to become infected than vaccinated cats [1]. Young kittens with an underdeveloped immune system can also be susceptible, as reported by VCA Hospitals [2]. Furthermore, the crowded conditions in many animal shelters can facilitate transmission between cats, making cats in shelters another high risk group according to a 2000 study [3].

Long-Term Effects

One of the biggest long-term effects of calicivirus in cats is the chronic carrier state. According to research from Cornell University, cats infected with calicivirus can remain carriers even after recovering from the acute infection and continue shedding the virus for months or years after (source). This allows the virus to continue circulating among cats. One study showed calicivirus remained prevalent in colonies of cats over long periods despite widespread vaccination (source).

In addition to being chronic carriers, cats who have had calicivirus often experience recurring symptoms throughout their lives. Stress or other illnesses can trigger relapses of oral ulcers, nasal discharge, and fever. Some cats have chronic nasal congestion or discharge due to permanent damage to their nasal tissues from the initial infection. Recurring symptoms tend to be milder than the acute illness.

When to See a Vet

Severe symptoms of calicivirus often require veterinary attention. Signs that warrant a trip to the vet include:

High Fever – Fevers over 103°F can lead to dehydration and should be addressed quickly. Bring your cat to the vet if its temperature is persistently over 103°F. They can provide fluids and medicine to reduce the fever.

Not Eating/Drinking – Appetite loss is common with calicivirus, but cats cannot go more than 2-3 days without food and water. Seek veterinary care if your cat is refusing all food and water for over 24 hours. The vet can give appetite stimulants and provide subcutaneous fluids.

According to VCA Animal Hospitals, veterinary hospitalization may be required for cats with severe calicivirus infections. Intravenous fluids, nutritional support, and intensive nursing care can help stabilize seriously ill cats until they start to recover.

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