Feline Infectious Peritonitis (FIP) is a disease that kills 1 in 100 to 1 in 300 of all cats under ages 3-5. The incidence can be five to 10 times greater among young cats coming from catteries and shelters. FIP is virtually 100% fatal, and there is no treatment or cure that is FDA approved. However, treatment options do exist. FIP can manifest suddenly — weeks, months or even years after initial infection. Therefore, cat lovers usually experience the heartbreak of this disease long after they have developed strong emotional bonds with their pets. If you and your veterinarian are suspicious of FIP, please contact FIP Warriors 5.0 on Facebook ASAP for options. 

History of Feline infectious Peritonitis 1963-2022 – First description to  Successful Treatment   


Niels C. Pedersen 


Center for Companion Animal Health, School of Veterinary Medicine, University of  California, 944 Garrod Drive, Davis, CA, 95616, USA 

April 17, 2022 




This article highlights knowledge of feline infectious peritonitis (FIP) as it evolved,  starting at its recognition in 1963 to present time, and was prepared with veterinarians,  cat rescuers and guardians, shelter staff, and cat lovers in mind. A brief mention is  made of the causative feline coronavirus and its relationship to a ubiquitous and  minimally pathogenic enteric coronavirus of felids, epizootiology, pathogenesis,  pathology, clinical features, and diagnostics. Major emphasis is on risk factors affecting  FIP prevalence, and the role of modern antiviral drugs in successful treatment.  




Feline infectious peritonitis (FIP) was described as a specific disease entity in 1963 by  veterinarians at the Angell Memorial Animal Hospital in Boston (Holzworth 1963) (Fig.  1). Pathology records from this institution and The Ohio State University failed to identify  earlier cases (Wolfe and Griesemer 1966), although identical cases were soon  recognized worldwide. The initial pathologic descriptions were of a diffuse inflammation  of the tissues lining the peritoneal cavity and abdominal organs with extensive  inflammatory fluid effusion, from which the disease was ultimately named (Wolfe and  Griesemer 1966, 1971) (Figs. 2,3). A second, and less common clinical form of FIP,  manifested by less diffuse and more widespread granulomatous lesions involving organ  parenchyma was first described in 1972 (Montali and Strandberg 1972) (Figs.4, 5). The  presence of inflammatory effusions in body cavity in the common form, and lack of  effusions in the less common form, led to the names wet (effusive, non parenchymatous) and dry (non-effusive, parenchymatous) FIP. 


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Note: There is a desperate need for these drugs, but the demand has gotten way ahead of the procedures necessary to bring them safely and economically to the marketplace. It takes 2-7 years to get approvals and market a drug after it is researched in Western countries and the worldwide problems with FIP are only getting worse. This is especially true in advancing countries where the demand for purebred kittens has gone through the roof and the conditions favoring FIP have gone with it. GC376 and GS-441524 are being illegally produced in China and sold through subsidiaries in Europe and US. Manufacturers and secondary suppliers often state that these drugs are to be used for research purposes only, not for human use, or not for veterinary or human applications. However, they are well-aware of their great demand and willingness of many cat owners to pay a high price. The purity or biological activity of these drugs is not assured, and veterinarians (or owners) have no prior experience with preparing them for treatment or using them to treat cats with FIP. The ethical aspects of using black market drugs, even if purchased by owners, is a problem that veterinarians have to confront. Ethical considerations have led many owners to treat their cats without veterinary input, which is unfortunate as the treatment is long, not without side-effects, and must be carefully monitored with regular blood tests.


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