FIP is one of the most challenging diagnoses for veterinarians. This is because the disease is complex and the current tests have limitations. That is why, sometimes, FIP is a diagnosis by exclusion. Meaning that the vet eliminates from the list all the diseases that mimic PIF.

1. Veterinary Advice on FIP in Cats (Feline Infectious Peritonitis)
Feline Infectious Peritonitis (FIP in cats) is a severe, debilitating, and progressive
disease. In most cases, with a fatal outcome.
Distributed worldwide, it specifically affects felines, both domestic cats (Felis
catus) and wild cats (lynxes, leopards, pumas, cheetahs, etc.). Cats of all ages
can become ill. But, FIP symptoms in kittens are more frequent, in ages between
2-3 months to 2-3 years.
In this article, we will discuss in depth everything you need to know about FIP. A
disease that is as alarming for cat owners as it is devastating for felines.
How do Cats Get FIP?
FeCV lodges in the intestine of cats and causes a chronic infection of the
digestive cells. It does not produce symptoms or generate self-limiting transient
diarrhea.

2. Due to random errors during replication in the digestive cells, the FeCV can
mutate, giving origin to a pathological and harmful viral form. This new virus can
travel through the cat's intestinal wall invading the White Blood Cells and
disseminating throughout the animal's body. This gives rise to the disease called
Feline Infectious Peritonitis (FIP).
The cat's immune system detects the virus and generates antibodies against it.
But these antibodies are "non-neutralizing". They cannot prevent viral replication.
It is the cat´s own inflammatory reaction that produces the symptoms of the
disease.
How is FIP Transmitted?
FeCV is very contagious. The most frequent form of transmission is the fecal-oral
route. Most felines shed the virus in feces for only a few months, but a small
percentage shed the virus for life.
The second, less frequent transmission route is through oro-nasal secretions
(saliva and mucus).
Finally, transplacental transmission from mothers to kittens. This route still needs
confirmation with further studies.
The virus is fragile in the environment and dies in approximately 24 to 36 hours
outside the host's body. But it can live for several months in cold climates that
preserve its vitality.
The virus enters the body of healthy cats by ingestion or inhalation. The direct
form of contagion is close contact with carrier animals. The indirect way is
through objects contaminated with feces (sandboxes, feeders, bedding, etc.).