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FIP in short

DVM, PhD Suvi Pohjola-Stenroos
Felina Cat Clinic
Finland

FIP is a disease caused by corona virus, actually there are hundreds of different corona viruses but only 7-8 strains of them produce FIP. FIP means feline infectious peritonitis. The mechanism is actually vasculitis, that is inflammatory reaction in the wall of the blood vessel. This reaction will cause fluid to escape from vessels to cavities. The symptoms are either wet (fluid in cavities: thorax, abdomen) or dry (inflammatory lesions in different organs) or mixed from both. The final diagnosis can only be confirmed by biopsy, so has it been done? Several other things can produce similar changes, even the blood work can be misleading, the only way to say finally this is a FIP case, is to take biopsies and to see vasculitis.

If I take blood samples from 100 cats, 94 will have antibodies against corona viruses. They really are common. Where as the loses from real FIP in catteries with high frequency of antibodies are only between 4-5 %. So FIP is not often an epidemic, it is more like an immunological disease, the suffering animal having an not properly working immunity.

What happens in catteries? The adult cats may have corona viruses, some of them may secrete them in their stools without any symptoms. The kittens born to a latent carrier queen will be protected by the colostral antibodies (passive transfer occurs during the first two days and after this secretory IgA covers their intestinal mucosa). The immune system of the kittens develops from birth to about 4-6 weeks, after 4 weeks the kittens have lost the maternal protection from milk antibodies almost totally. This is the critical time.

If there is a very heavy load of viruses, poor management (nutrition, overcrowding), to much inbreeding (inherited bad immunity e.g. T-cell based immunity) the kittens will be infected with corona viruses. But only in 4-5 % of the infected kittens the infection will lead to a clinical disease (those kittens have T-cell dysfunction either from the genetic reasons or poor management and exhaustion of the immunity). In those kittens the virus takes mutations and causes the clinical disease.

The incubation time ( from getting the virus to the clinical disease) can be anything between 2 weeks and years. There is no treatment to the clinical FIP.

In a cattery situation: If cases of confirmed FIP exist: separate the queen from her babies when the babies are four weeks, also separate them from all the other cats until they leave the house (The only way to produce clean kittens in problem catteries with subclinically infected queens). Have good management (premium diets, not to many cats, cats in smala groups, no outdoor cats, only FeLV negative cats etc.). Do not produce kittens from the same parents that produced the kitten with immune dysfunction, the immunity will be inherited. Keep cats in separate groups in larger catteries: 3-4 cats in separate room or more preferably, have own toilets and water and food bowls for every cat. The transmissions of the virus is by fecal-oral route mainly.

The serology can be used as a screening method: in catteries were cats have antibodies against FIP: only acquire cats from other catteries with antibodies against FIP. If your cattery has no antibodies against FIP, acquire cats from catteries with 0-titer. The titer means a certain risk > every 10. cat with a titer has the probability to develop FIP, because it already has the contact with corona virus. It will depend from the cats immune system whether the cat will have the clinical disease or not.

Do not vaccinate cats against FIP. Vaccination will generally cause antibodies to develop, BUT, FIP cats have poor immunity and do not develop antibodies properly, and also the protection is mainly influenced by the T-cells (or their lack) and vaccination has no effect on them. Dr. Legendre from Tennessee had a lecture in Utrecht in 1994 about the FIP vaccine on the U.S. market: the vaccinated kitten group had the clinical disease more often than the unvaccinated control group after the contact with the virus. The vaccinated group had the vaccine as an immunosuppressive tool against the already poor immunity.

To my mind the only way to prevent cases is to take care of the immunity, we can not get rid of the microbes. One way in the problem catteries could be also stimulating the T -cell immunity, this is under research among the other things.

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