Caliciviruses are common viruses in cats. They are partly responsible for coryzas, diseases of the upper respiratory tract. While calicivirus infections may be asymptomatic, serious forms exist which can lead to the death of the animal if left untreated. Most of the time, a consultation with a veterinarian is essential to treat the animal. Here are some keys to better identify and treat your animal.

Caliciviruses are small viruses made up of a strand of RNA. They are naked viruses, that is to say they do not have a lipid envelope. This absence of envelope makes them extremely resistant in the external environment.

Caliciviruses are responsible for respiratory diseases of the upper tract. In cats, there are mainly two ways of infection:

• By direct contact with a shedding cat. The difficulty in controlling this virus comes from the fact that shedding animals can sometimes be asymptomatic. Indeed, a cat can continue to shed viruses for up to 30 months after its infection. Caliciviruses are then present in the nasal, ocular and oral secretions of cats;
• By contact in the environment, where the virus can survive for a very long time, even without contact with animals.

The first symptoms usually appear quickly, 2 to 4 days after infection.

When alone, the calicivirus causes mild coryza with a watery, transparent eye and nasal discharge, and moderate inflammation of the oral mucosa.

When combined with other infectious agents such as herpes viruses, reoviruses or chlamydophila, calicivirus can trigger more serious infections. In these cases, the coryza can take two forms:

• An acute form, with the appearance of difficulty in breathing, inflammation of the mucous membranes and profuse discharge from the eyes. Often the cat will stop eating due to the lack of smell and mouth pain;
• A chronic form, often complicated by multiple bacterial infections. The cat will then present with a chronic discharge, sinusitis and may present noise when breathing.

To these already complex forms can be added bacterial infections which then worsen the condition of the animal and its prognosis.

The presence of coryza, or a calicivirus infection is an important reason for consulting a veterinarian. Unfortunately, there are no effective antiviral treatments for caliciviruses. The veterinarian will then have to put in place a supportive treatment to help the animal while its immune system fights against the viruses. This treatment can consist of anti-inflammatory drugs to reduce pain associated with stomatitis and ulcerations, and antibiotics to fight against possible secondary infections.

In addition, it is essential to stimulate the food intake of the animal. If the cat is no longer eating, the veterinarian can then choose to add an orexigenic treatment or to put a feeding tube. For this, it is sometimes necessary to hospitalize the animal while its condition improves.

In addition to these medical measures, the owner must carry out an important cleaning of the eyes and nose of the cat, in order to eliminate what could bother him or obstruct his breathing.

The prevention of a possible reinfection passes by a rigorous cleaning of the environment of the animal. Due to their characteristics, caliciviruses are resistant to usual soaps and cleaners. They can nevertheless be destroyed by prolonged contact with bleach, but this is difficult to apply to the entire environment of the cat (outdoors, etc.).

Thus, treating a cat with coryza is not easy and re-infections are frequent. The best treatment therefore remains prevention in order to avoid the first contamination of the animal. 

For this, it is advisable to systematically vaccinate your animal, regardless of its lifestyle (indoor or outdoor). The vaccine then makes it possible to limit the contamination of the animal, but also to limit the reactivation of the virus in cats already contaminated. A first vaccination from 8 weeks is recommended, followed by two boosters spaced one month apart. Then, the animal should be vaccinated annually. This protocol can be adapted by your veterinarian according to the situation of each animal.