An orange and white cat limps.

Feline Calicivirus: Signs of Infection and Causes of Limping in Cats

Feline Calicivirus (FCV) is a virus that causes upper respiratory tract infections (URI) in cats. Along with Feline Herpesvirus, these two bugs are responsible for almost all URIs that affect felines. Feline Calicivirus belongs to the family Caliciviridae, which shares similarities to the human norovirus. A more severe and rare form of Feline Calicivirus, known as FCV-associated virulent systemic disorder (FCV-VSD) was identified in California in the late 1990’s.

How Does the Virus Spread?

Calicivirus is spread through direct contact with saliva, nasal, or ocular discharge from infected cats. The virus can also be spread through aerosolized particles from sneezing. Most infected cats can shed the virus for 2-3 weeks, but some may be carriers and shed the virus for months. The virus can live on surfaces for months as well, not to mention humans, and can act as an inadvertent fomite. It can also be transferred by communal sharing of food bowls and bedding.

What Are Symptoms of Calicivirus in Cats?

During the initial stages of infection, clinical signs may include:

The initial stage of illness usually lasts 7-10 days. After initial stages, clinical signs should slowly improve. Appetite and energy levels will pick up daily as the course of the virus comes to an end. Calicivirus can cause miscarriage in pregnant cats.

Cats that contract the more severe form of Calicivirus (FCV-VSD) can suffer diffuse organ injury, which can be fatal.

Clinical signs of the more severe FCV-VSD include:

How Is Calicivirus Diagnosed?

If you suspect that your cat has FCV or is showing signs of an upper respiratory tract infection, they should be evaluated by a veterinarian. FCV is commonly diagnosed by a physical examination and compatible clinical signs. A confirmatory diagnosis can be obtained by collecting swabs from the cat’s mouth, nose, and eyes. The lab will isolate the virus if present and a report will be sent to your veterinarian within a week. The lab cannot distinguish between the mild form of FCV and the more severe FCV-VSD.

How Is FCV Treated?

Most cats will recover on their own from this virus. Cats are often prescribed antibiotics to help prevent secondary infections or to treat pneumonia. In more severe cases or in elderly cats, the animal may need to be hospitalized to prevent dehydration and help with nutritional support.

Keeping your cat’s nose and eyes clear of discharge is a good at-home measure to help with recovery. Be sure to clean the nose and mouth with warm water-soaked gauze, and utilize nebulization to open airways. This can be achieved by turning your shower to hot and closing the bathroom door to allow the steam to build up. Then, take your cat into the bathroom for 5-10 minutes to allow the steam to open their airways and break down mucus. DO NOT put your cat in the shower or submerge them in water.

Cats with FCV may be reluctant to eat due to oral ulcerations, elevated temperatures, and nasal congestion. Offering them aromatic, wet cat food, or spoon feeding them baby food, may be helpful.

Is There a Vaccine for FCV?

There is a vaccine for FCV, which is considered part of the core vaccines for kittens and cats.

Diseases that fall into the core vaccines for cats include:

The American Association of Feline Practitioners (AAFP) recommends kittens be vaccinated with the core vaccines (FPV, FHV, FCV) at 6-8 weeks of age and then again every 3-4 weeks until they are 16 weeks old. Adult vaccines are administered at 1 year of age and then every 3 years. Your veterinarian may recommend a modified schedule based on your cat’s exposure risk and underlying health concerns. The rabies vaccine schedule is slightly different, since it occurs once at 3 months of age, then at 1 year of age, and then every 3 years.

Why Do Cats with Calicivirus Limp?

Cats that are infected with FCV may limp in some cases. This can be due to limb swelling, or be secondary to ulcerations on paw pads or a localized infection (abscess). If your cat is limping, this is commonly accompanied by pain and they should be assessed by a veterinarian immediately to determine if they need pain medications. The limping should resolve as they start to feel better and the infection works its way out of their system.