Calicivirus in Cats: Symptoms and Treatment

If your new cat isn’t doing well, they may be affected by calicivirus.  

Calicivirus in cats is a common virus in newly adopted furry family members that can lead to respiratory signs, limping, and decreased appetite.  

Medications may be needed to help alleviate feline calicivirus symptoms and help your cat feel better. 

Let’s look at everything you need to know as a pet parent. 

What Is Calicivirus in Cats?

Calicivirus in cats is a viral pathogen that causes upper respiratory tract infection in cats. Infection most commonly resembles a cold, but severe infections involving the lungs, joints, and/or other organs can occur.  

Feline calicivirus is most found in facilities that house multiple cats, such as rescues, shelters, or breeding facilities. 

However, it can spread readily in households with only a few cats. 

Kittens and young adult cats are usually at the highest risk for infection, but a cat of any age can be affected.  

Symptoms of Calicivirus in Cats

Some pets become infected and do not show any clinical signs of calicivirus in cats. If there are signs, they can range from mild to severe, with severe signs resulting in death. 

The most common symptoms of calicivirus in cats are:  

• Sneezing  

• Nasal discharge  

• Ulceration of the surface of the nose (skin broken open)  

• Conjunctivitis (eye inflammation)  

• Eye discharge 

An affected cat may also develop the following:  

• Ulcers on the lip, tongue, or elsewhere in the mouth, often accompanied by drooling  

• Fever  

• Lethargy   

• Dehydration  

• Poor appetite due to severe nasal congestion and/or oral ulcerations  

The following signs are associated with more severe cases:  

• Pneumonia, with a cough or difficulty breathing  

• Joint inflammation, which causes limping or swelling in the affected joint(s)  

• Signs related to blood vessel wall inflammation (vasculitis), which can lead to multi-organ failure and death, including:  

  • Swelling in the face/legs  

  • Skin wounds  

  • Bloody nose  

  • Bloody stool  

Causes of Calicivirus in Cats

Calicivirus in cats is shed in secretions from the nose, mouth, and eyes. A cat can become infected by contact with secretions containing the virus directly from another cat or indirectly through contact with an object (carrier, food/water bowl, surface) that has been contaminated with infectious secretions. 

Once inside a cat’s body, calicivirus invades the cells of the nose, throat, mouth, and tonsils. 

More aggressive strains of calicivirus can invade the lungs, joints, and kidneys. Signs of illness usually develop two to six days post-exposure. 

There are multiple strains of calicivirus in cats, and sometimes more than one strain may be infecting pets in the same environment. 

Calicivirus can mutate into a new strain in a cat’s body. There are differences in virulence or disease-causing ability between strains, ranging from mild to severe.  

How Veterinarians Diagnose Calicivirus in Cats

Vets diagnose calicivirus in cats using the following methods: 

• Lab work, such as a complete blood count (CBC) and chemistry, will not directly test for calicivirus in cats but may be helpful in determining if there is concurrent illness.  

• Chest radiographs (X-rays) may be recommended if a cat presents with a history of cough, but the findings will not be specific for FCV. Pneumonia can be diagnosed with chest X-rays.   

• Blood tests that measure FCV antibody levels (titers) can be performed, but a positive or elevated titer can happen with both natural exposure and vaccination. It’s impossible to determine the difference using this test alone.   

• A polymerase chain reaction assay (PCR) can be performed using swabs from the nose, the inside of the eyelids, and/or the mouth. PCR testing can also be performed on blood, feces, and urine early in the disease process.  

Keep in mind that a large percentage of healthy cats are long-term carriers of FCV. So just because you find FCV on the test does not mean it is necessarily causing the clinical signs.  

Treatment of Calicivirus in Cats

Supportive care is the gold standard of treatment for calicivirus in cats. Supportive care includes: 

• Place your cat in a warm, steamy bathroom for 10–15 minutes twice daily to help reduce nasal congestion.  

• Nutrition is important because an affected cat with oral ulcerations and nasal congestion may not want to eat. Offer a variety of very strong-smelling foods. Canned food warmed up slightly may be more enticing than cold canned food or dry food.  

• Use warm wet cloths to clean away eye and nose discharge. When cats are not feeling well, they do not want to groom, especially if they also have oral ulcers.  

Antiviral medication is not commonly used in the treatment of calicivirus in cats, though some medications may be useful, including:  

• Pain medication. This is given to cats with oral/nasal ulcerations to provide comfort.  

• An oral antibiotic can be used to treat secondary infections (nose, lungs, mouth). Your vet may prescribe antibiotics like Clavamox or azithromycin if they suspect a bacterial infection on top of the calicivirus. 

• Topical eye antibiotic medication will be prescribed for cats with eye infections, like tobramycin drops or terramycin ointment. 

• Oral nonsteroidal anti-inflammatory medication may be used to reduce inflammation and fever, like Onsior tablets, given once a day for three days.   

• Intravenous or subcutaneous fluids may be indicated if a cat is dehydrated. IV fluids can also help in fever reduction.  

Recovery and Management of Calicivirus in Cats

Most cats will recover from calicivirus in cats in seven to 10 days. However, cats can become carriers and shed virus from oral and nasal secretions long term. 

Cats that become chronic carriers may develop oral inflammation (gingivitis/stomatitis) and be at increased risk for growths in the nose, mouth, or ear (nasopharyngeal or aural polyps).  

Vaccination can help prevent the spread of FCV. A vaccinated cat can still become infected with calicivirus but not develop any clinical signs or may have mild signs compared to unvaccinated cats.  

FCV is highly contagious, so it’s important to isolate the affected cat, either in a bathroom or bedroom, to avoid exposure. 

Remember that you can spread the virus to unaffected cats after contact with your infected cat if you do not wash your hands or change your clothes after interaction.  

All materials that have encountered the infected cat need to be thoroughly washed. 

The virus can live in the environment on surfaces for one to four weeks and is not killed by regular cleaners. 

Bleach solution (1 part bleach to 32 parts water) can be used to wipe down surfaces and clean materials like bedding, litter boxes, and food and water bowls. 

Prevention of Calicivirus in Cats

Vaccination is an important part of prevention of calicivirus.  

While some cats may still become infected after being vaccinated, the vaccine can help affected cats' immune systems fight the virus faster and allow them to experience less symptoms. 

Minimizing overcrowding of cats is also helpful to reduce their exposure. Overcrowded cats are more stressed and it’s easier for viruses to spread from cat-to-cat. 

When getting a new cat, look at how healthy the overall population of cats appears from the facility you're adopting/purchasing your cat from.  

Do they have room to breathe? Are there lots of snotty cats with runny eyes?   

Remember, upper respiratory viruses are very common in cats and easily spread cat-to-cat.  

Reduce your cat’s exposure by keeping them away from other cats and wash your hands after handling other cats before coming home to your pet.