Feline Infectious Peritonitis (FIP) is a severe disease that affects cats globally. It arises from a mutation of the common feline coronavirus (FCoV), widely present in cat populations. While FCoV typically causes mild or no symptoms, its mutation into FIP can lead to widespread inflammation and organ failure, which is often fatal for affected felines.
The Current FIP Vaccine Landscape
A vaccine for FIP, known as Primucell® FIP (also marketed as Felocell FIP), is currently available. This vaccine is an intranasal, modified-live virus formulation that is temperature-sensitive. It is designed to be administered into the cat’s nasal passages. The United States Department of Agriculture (USDA) has approved this vaccine for use. The vaccine aims to provide protection against FIP in cats that have not yet been exposed to feline coronavirus.
The administration protocol for Primucell® FIP involves two doses given three to four weeks apart. This vaccine is specifically licensed for cats aged 16 weeks or older. After the initial series, annual revaccination is generally recommended by the manufacturer. However, its use is not widespread and is often limited to specific situations.
Understanding the FIP Vaccine’s Efficacy and Usage
The efficacy of the FIP vaccine has been a topic of considerable discussion among veterinary professionals. Studies show varying protection, with some indicating partial effectiveness against low viral doses. Some research suggests it may prevent FIP deaths in 50-75% of vaccinated cats under certain conditions. However, its ability to protect against high viral loads or in highly prevalent FCoV environments, like endemic catteries, is not consistently demonstrated.
Vaccination is considered for cats in high-risk environments where FCoV is common. These settings include multi-cat households, breeding catteries, and shelters. For the vaccine to be most effective, it should be given to kittens that are at least 16 weeks old and, ideally, are seronegative for FCoV, meaning they have not yet been exposed to the virus.
Why Widespread Vaccination is Not Standard
Despite the FIP vaccine’s existence, it is not a core vaccine and not routinely recommended for all cats. A primary reason is the complex nature of FCoV and challenges in developing a highly effective vaccine. The vaccine targets the initial FCoV infection, rather than the mutation of the virus that directly causes FIP. Many kittens are exposed to FCoV at an age younger than the recommended vaccination age of 16 weeks, rendering the vaccine less effective for them.
The single commercial vaccine uses a serotype II strain, while a majority of FIP cases are caused by serotype I strains. Concern exists regarding Antibody-Dependent Enhancement (ADE), where vaccination-produced antibodies could worsen the disease if a vaccinated cat encounters a virulent strain. These factors, coupled with the need for multiple doses, contribute to veterinary associations often not recommending the FIP vaccine for general use.
Broader FIP Prevention Strategies
As the FIP vaccine is not a universal solution, other preventative measures focus on managing FCoV infection. Maintaining hygiene in multi-cat environments is a primary strategy. This includes daily cleaning of litter boxes and regular disinfection of shared spaces and objects. Prompt removal of feces is particularly important, as FCoV spreads primarily through the fecal-oral route and can survive in dried feces for several weeks.
Reducing stress for cats is a significant preventative step, as stress can contribute to FIP development in FCoV-infected cats. This involves providing adequate space, enrichment, and stable social groups, especially in multi-cat settings. Controlling cat population density, aiming for groups of no more than three to five cats, can help limit viral circulation. Testing new cats for FCoV before introduction into a household, particularly in breeding catteries, can help prevent viral spread. Preventing FCoV infection is considered the most effective way to prevent FIP.