What are the signs of FIP?

Signs of FIP arise weeks, months, and in rare cases years after initial infection. During this quiescent stage, the cat may be asymptomatic or suffer from vague signs such as stunted growth or increased susceptibility to other common infections. Many believe that FIP can cause upper respiratory disease signs during its early stages; this is not technically correct, because upper respiratory disease is usually caused by herpesvirus, chlamydophilla, mycoplasma, etc., and not directly by FIPV.


With time, many cats win their battle with this infection, while others lose. However, “losing the battle” may occur over a very long period of time; only terminally, when the cat’s defences collapse, do the more characteristic signs of FIP develop. This capitulation to the virus explains why cats with FIP seldom recover because a loss of immunity is extremely difficult to reverse. Although unappreciated in the past, we now know that cats in the terminal stages of FIP are often severely immunocompromised. This explains why common bacterial infections may complicate the disease picture in cats with FIP.


Cats who develop clinical cases of FIP may initially show nonspecific symptoms such as growth retardation, loss of appetite, depression, rough coat, weight loss, a fluctuating antibiotic resistant fever, and increased susceptibility to secondary infections (such as respiratory disease). More specific signs of FIP vary depending on the form of the disease (wet vs. dry) and the organs that are involved.


The most common form of the disease is referred to as “wet FIP.” Wet FIP is caused by inflammation of the linings of the abdominal viscera, and less commonly of the thoracic organs. This inflammation exudes large volumes of a characteristic mucinous, yellow-tinged fluid (exudate). Therefore, the major clinical sign in the wet form of FIP is ascites and abdominal distension (abdominal involvement) or dypnea (thoracic involvement).


FIP can also take a more chronic form referred to as “dry FIP”. Dry FIP, as the name implies, is not associated with fluid accumulations in the abdomen or chest, but rather with more localized masses in the kidneys, spleen, liver and terminal bowel, eyes, and the linings of the lungs and heart, and central nervous system. Uveitis (intraocular inflammation) can affect the eyes, making them look cloudy and changing the colour of the iris. Inflammation can enter the brain and spinal chord and cause a spectrum of progressive neurologic abnormalities. FIP accounts for over one-half the cases of inflammatory intraocular and nervous system disease in cats under 3-5 years of age.


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