This is a common viral infection in cats, and all unvaccinated cats are susceptible to the disease. Cats become infected by ingesting the virus shed by other infected cats living in closed proximity. Cats infected with the Calicivirus develop a disease of the respiratory system (akin to a bad cold) with severe eye infection, where the cat finds it painful to open the eyes. There are also ulcers on the tongue, so that the cat drools and cannot eat. They may develop pneumonia as well. Some cats, especially kittens, develop arthritis as a result and are unable to walk.
Treatment for calicivirus infection is primarily supportive, with antibiotics to control secondary bacterial infections and with medication to boost the immune system. Severely affected animals may need to be hospitalized to be given fluids and medication intravenously.
Vaccination is highly effective in preventing calicivirus infection.