Here are the diseases against which cats are most frequently vaccinated:

Herpesvirus, calicivirus and chlamydia: These are upper respiratory infections similar to the common cold for humans. They are very contagious and can cause fever, loss of appetite, nasal and eye discharge, etc. Younger cats are more severely ill. Pets that have suffered from these diseases can remain carriers for the rest of their lives and have periodic relapses of varying degrees of severity.

Feline panleucopenia: Sometimes called “feline distemper”, this very serious viral disease can have of mortality rate of 90 to 100% in unvaccinated cats, particularly kittens. For this reason, it is considered the most dangerous viral disease affecting cats. Symptoms may include depression, loss of appetite, uncontrollable vomiting and diarrhea, often with blood and severe abdominal pain. Treating this disease is difficult and costly. The virus may contaminate the environment where it can retain its infectiveness for up to a year, so that another cat could catch the disease. Fortunately, the vaccines are usually very effective.

Rabies: Rabies is a fatal and untreatable disease affecting the central nervous system, to which most mammals, including cats, dogs and humans, are susceptible. It is transmitted by the saliva of infected animals through bites or contact with a wound or a sore. The most common carriers are bats, raccoons, skunks and foxes. It is particularly important to keep bats in mind as they can easily slip into houses, even in the city, and cats are particularly adept at finding them. Rabies vaccines are required for pets travelling outside of the country.

Feline leukemia: This viral disease is one of the major causes of deaths in North America. This viral disease attacks the immune system and leaves the cat vulnerable to secondary infections, leukemia and tumors. Death often occurs within three years of infection. Some cats can also be infected and show no signs at all because several months or years can pass between the moment when a cat is infected and the time it starts to show symptoms. During that period, the cat is not “sick”, but is nonetheless contagious for all other cats because the transmission of the virus usually occurs through contact with other cats. Those cats that live in multi-cat households or are allowed outdoors are thus particularly at risk. It is generally recommended to have a cat tested before having it vaccinated, as it doesn’t need vaccination and should be isolated from other cats if it already carries the disease.