Feline calicivirus: symptoms, treatment, prevention

Article written by Veterinary Doctor Isabelle Vixège

Feline calicivirus is a widespread disease caused by a virus. Highly contagious, this virus is transmitted through nasal and oral secretions. Classically, it is responsible for coryza or gingivitis. While there is no specific treatment, veterinarians have vaccines against this feline virus.

1. What is it?

Calicivirus is a contagious infectious disease in cats; it is caused by a virus called calicivirus. This microbe is responsible, along with other entities, for the feline coryza syndrome.

This microorganism is very resistant in the external environment; it can survive for several days to weeks in the environment. It is also capable of mutating, producing different variants.

Did you know? The name calicivirus comes from the Greek kalux, meaning calyx. Calicivirus indeed shows concave facets in the shape of a flower calyx (a kind of crown of "green petals" at the base of the flower) under an electron microscope.

2. Transmission of feline calicivirus

Contagion is very high: calicivirus particularly thrives in animal communities (shelters, breeding facilities). It can infect up to 90% of cats there. However, any cat that goes outside and interacts with other cats can be contaminated one day.

The virus is transmitted through:

• Direct contact: from cat to cat via the nasal, oral, and ocular secretions of sick or carrier cats.
• Indirect contact: via contaminated premises, cages, fabrics, hands, etc.

An infected cat will harbor the virus for several weeks to several months, or even years, after apparent recovery; this means it is still contagious.

3. Symptoms of the disease

Classically, calicivirus manifests as feline coryza:

An infected cat shows a kind of cold (fever, sneezing, stuffy nose, conjunctivitis…). In the case of calicivirus, this clinical picture is complicated by ulcers in the mouth, especially on the tongue. These aphthous ulcers are painful and lead to anorexia (loss of appetite). The disease is more serious in kittens.

Among the list of symptoms, calicivirus can sometimes cause transient lameness.

Calicivirus is also believed to be involved in chronic feline stomatitis. This disease, still poorly understood, results in stubborn inflammation of the gums (gingivitis) and the back of the mouth. Calicivirus is often detected in the oral cavity of sick cats, but its involvement is not certain. The origin of feline stomato-gingivitis is complex and multifactorial (an autoimmune origin is also suspected).

A new hypervirulent form appeared in the late 20th century in the United States. Some cases have been observed in France. Symptoms include:

Ø High fever

Ø Edema (swelling) of the head and limbs

Ø Cutaneous ulcers

Ø Respiratory difficulties

Ø Kidney and/or liver damage

Ø Coagulation disorders

Ø High mortality

It seems that these forms of hypervirulent calicivirus are linked to a mutation of the virus. They appear in communities where population mixing, the number of animals, and poor hygiene are conducive to the emergence of a mutant.

4. Diagnosis

The diagnosis of feline calicivirus is clinical (based on symptoms). The veterinarian can also perform a PCR test on nasal secretions or a buccal swab.

5. Treatment

There is no specific treatment for feline calicivirus.

In cases of coryza, anti-inflammatory drugs are administered to relieve the infected cat, as well as antibiotics if bacterial superinfection is observed. "Small care" is important: cleaning eyes, nose, administering water and liquid food with a syringe. For the most affected animals, an IV drip or the placement of a feeding tube may be necessary.

Management of chronic stomatitis is complex, generally combining immunomodulatory drugs and dental care.

In the case of hypervirulent feline calicivirus, treatment involves hospitalization in intensive care.

6. Prevention and vaccination against feline calicivirus

In the absence of treatment, disease prophylaxis is of particular importance. It involves several aspects:

• Premises hygiene

In shelters, breeding facilities, or hospitals, the disinfection of equipment or cages must be rigorous. Bleach can be used. Hand washing is also essential.

• Quarantine of sick cats and new arrivals

Affected cats showing symptoms must be isolated. Staff must practice rigorous hygiene when moving from a contaminated area to an area containing healthy cats. New arrivals with unknown status must be confined for at least 3 weeks before joining the group.

These measures, however important, are not sufficient due to the possibility of healthy carriers who are potentially contagious.

• Vaccine

To protect your cat, there are several vaccines against feline calicivirus. They are coupled with another virus responsible for coryza in cats (herpes virus).

The WSAVA (World Small Animal Veterinary Association) recommends the following vaccination protocol for kittens:

Ø Injection of a dose at 8 weeks of age

Ø Booster at 12 weeks then 16 weeks

Ø Booster between 6 and 12 months

Boosters are then given once a year or once every 2/3 years for indoor cats.

Due to the possibility of mutants, vaccination against calicivirus may not be 100% effective. In most cases, it significantly reduces symptoms and the duration of virus carriage.

7. Prognosis and lifespan of a cat with calicivirus

The prognosis is good for the coryza form if treated appropriately (especially for kittens). Stomatitis does not threaten life expectancy, but can be very debilitating throughout the cat's life.

In hypervirulent calicivirus (very rare), the mortality rate reaches 30 to 50% of affected cats.

Vaccination against feline calicivirus remains the best protection against this disease for our four-legged friends.

Also read:

• Our guide to transporting cats

Isabelle Vixège, Veterinary Doctor