Spreads Like Crazy and Makes Your Pet Miserable — Is It Serious?

Spreads Like Crazy and Makes Your Pet Miserable — Is It Serious?

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  • Calicivirus infects the respiratory tract of cats, and is highly infectious
  • The virus is transmitted by direct cat-to-cat contact, through the air when an infected cat sneezes and also through contamination of objects the cat comes in contact with
  • Symptoms of infection in most cats include sneezing, runny nose, pinkeye, breathing problems and appetite loss
  • Most kitties infected by the calicivirus develop mild symptoms that don’t require treatment
  • More serious infections require hospitalization and stabilization

Editor's Note: This article is a reprint. It was originally published June 18, 2017.

Calicivirus, also called feline calicivirus or FCV for short, is a common respiratory disease seen in cats. Along with feline herpes virus, calicivirus causes the vast majority of upper respiratory infections in cats. The virus infects the respiratory tract, including the lungs and nose, the mouth (sometimes causing ulcers on the tongue), the intestines and the musculoskeletal system.

Calicivirus is highly infectious and is most often seen in shelters, catteries and other similar facilities where there are a lot of kitties housed together in a potentially very stressful environment. The disease can occur in cats of any age, but kittens over 6 weeks seem to be the most susceptible.

There is a vaccine against calicivirus that many veterinarians recommend. I am not one of them. The calicivirus vaccine is similar to the kennel cough vaccine for dogs in that there is ample evidence they are virtually useless in decreasing the prevalence of disease.

It's also important to know that repeated vaccinations against calicivirus don't necessarily offer more protection. Because the majority of cats are vaccinated against this virus when they receive a series of kitten core vaccines, continuing to revaccinate year after year does nothing to foster additional protection. I'm not a fan of repetitive calicivirus vaccinations.

How Calicivirus Is Transmitted

Calicivirus is spread in the air when an infected cat sneezes. As the droplets, which contain infective virus particles, fall to the ground, they contaminate the surfaces they land on. The virus can also exist on dust particles and dander. Calicivirus can also transfer to objects an infected cat uses, such as food and water bowls, litter boxes and bedding. Other cats who come in contact with those objects can then be infected.

Finally, the virus can be transmitted through direct contact between cats. If a healthy cat is exposed to an infected kitty's saliva, nasal or eye discharge, or poop, he can become infected. That's why if you have an unvaccinated indoor-only cat, it's really important that you don't expose her to, for example, a feral rescue cat or a stray you bring home.

Symptoms of Infection

The calicivirus mutates very easily, which means there are many different strains of the virus existing in nature, some of which cause more serious illness than others.

The virus most often manifests as an acute upper respiratory infection with symptoms that include sneezing, runny nose and pinkeye (conjunctivitis). Infected cats may also be lethargic, lose their appetite (because they can't smell due to all the congestion), run a low-grade fever and experience breathing difficulties and coughing spells. Very young kittens can develop pneumonia. Symptoms typically come on suddenly and can last from a few days to a few weeks. Additional less common signs of FCV can include:

  • Development of ulcers on tongue, hard palate, tip of nose, lips or around claws
  • Arthritis (inflammation of joints)
  • Painful walk

Rarely, calicivirus can manifest as a virulent systemic FCV infection, or vsFCV, which involves highly pathogenic strains of the virus. These mutations allow the infection to attack major organs and the cells that line blood vessels.

vsFCV can create severe disease, including pneumonia, hepatitis (liver inflammation), pancreatitis, swelling and ulceration of the skin and bleeding from the nose and intestines. Again, this manifestation is extremely rare. Most cats who contract the calicivirus have symptoms similar to a bad cold.

Diagnosing Calicivirus

Your veterinarian will take a thorough history of your cat's symptoms and perform a physical exam. He or she will also perform a complete blood count (CBC), a chemical blood profile and a urinalysis. An FCV antibody test will also be needed to evaluate the level of calicivirus antigen or antibodies in your cat's system.

A more advanced test can also be performed that involves growing isolated viruses using a technique called cell culture. Your vet may also take a chest x-ray to check for changes in your cat's lung tissue or to rule out pneumonia.

Treatment Options

Thankfully, most cats with calicivirus have mild infections and don't require veterinary care. But kitties who develop pneumonia or bleeding problems will need to be hospitalized and stabilized. Secondary infections, if present, must also be managed. Sometimes young kittens need a round of intravenous (IV) fluids to correct dehydration, along with nutritional support.

Steam inhalation or nebulization with colloidal silver can be very effective for cats with severe nasal congestion, especially kittens. I also use homeopathic nosodes in these situations with really nice results. Immuno-stimulants, such as olive leaf and arabinogalactans, can also be very helpful.

Cats recovering from a calicivirus infection require excellent nursing care, including cleaning around the eyes and nose to prevent a buildup of gooey secretions. Cats with FCV should be encouraged to eat, especially if they can't smell their food. Gently warming the food can help, along with raising the bowl so the aroma is closer to kitty's nose. You can also add some bone broth or gently cooked chicken or a topper to encourage your cat to eat.

The prognosis for cats with calicivirus depends on the severity of symptoms. Most kitties recover in about a week, but in very serious cases, it can take several weeks for kitty to make a complete recovery.


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