Feline infectious peritonitis (FIP) is not usually caused by a cat suddenly catching a completely unfamiliar virus from outside. Most cats have been exposed to feline coronavirus (FCoV), and many cats can carry the virus without becoming seriously ill.
In most healthy cats, feline coronavirus causes few or no noticeable problems. In some cats, however, the virus can change inside the body, and the cat’s immune response may contribute to the development of FIP.
Several factors may increase the risk or place additional stress on a cat’s body:
A. Changes in the environment
Moving to a new home, being boarded, changes in living conditions, or spending long periods in a confined environment can be stressful for some cats.
B. Ongoing emotional stress
Conflict between cats in the same household, frightening experiences, or prolonged anxiety can put additional stress on a cat.
C. Physical or nutritional stress
Poor nutrition, repeated digestive problems, prolonged loose stools, or general weakness may affect a cat’s overall condition.
D. Immature immune systems in young cats
Kittens and newly adopted cats may be more vulnerable during periods of major change or stress.
In simple terms, FIP is generally understood as a complex interaction between feline coronavirus, the virus changing within the cat, and the cat’s immune response. It is not as simple as a healthy cat simply “catching FIP” from another cat.
FIP can cause inflammation throughout the body and may affect different organs and body systems. Recognizing concerning changes early and seeking veterinary evaluation can help you understand what may be happening and what support your cat may need.