Feline Infectious Peritonitis (FIP)
Learn what the condition is, how it may be detected early, how it is treated or managed, and which breeds or species are linked to it.
Condition snapshot
A concise guide to the condition’s pattern, detection, management and urgency.
Reduce feline coronavirus exposure pressureRoutine isolation of a cat with FIP is not usually required; prioritise litter hygiene, reduced crowding and veterinary advice.
Emergency presentation is possibleBreathing difficulty, collapse, seizures or rapid neurological deterioration requires emergency veterinary care.
This snapshot is a general guide, not a diagnosis or treatment plan. New, severe or worsening signs require veterinary assessment.
About the condition
Feline infectious peritonitis, or FIP, is a serious disease that develops in a small proportion of cats infected with feline coronavirus. Common feline coronavirus usually lives in the intestine and may cause no signs or mild diarrhoea. In cats that develop FIP, viral changes within the individual cat and an abnormal immune response allow infected cells to spread inflammation through the body.
FIP can appear in several forms. Effusive disease causes protein-rich fluid to accumulate in the abdomen or chest, leading to abdominal enlargement or breathing difficulty. Non-effusive disease can produce inflammatory lesions in organs such as the kidneys, liver, lymph nodes, eyes or nervous system. Fever, weight loss, poor appetite and lethargy are common but not specific.
In some cats a definitive tissue diagnosis is impractical, so veterinarians work with a graded level of diagnostic confidence.
FIP was once considered almost uniformly fatal, but that has changed dramatically. Effective antiviral treatment with nucleoside analogues such as GS-441524 has transformed prognosis, with high recovery rates when an appropriate product and protocol are used under veterinary supervision. Availability and legal access vary between countries.
The cat with FIP is not usually treated as directly contagious in the way a cat with panleukopenia would be. The widespread enteric coronavirus is what spreads between cats; FIP generally develops after changes occur within the infected individual.
The major shift in modern FIP care is therefore therapeutic as well as diagnostic. A disease that once carried an almost uniformly hopeless prognosis now warrants rapid investigation specifically because effective antiviral treatment exists.
Persistent fever, unexplained weight loss, abdominal or chest fluid, jaundice, eye inflammation and neurological signs are important FIP presentations, particularly in younger cats from multi-cat environments. Response to therapy can then provide additional support.
Screening & Early Detection
No single routine screening test can tell which coronavirus-exposed cat will develop FIP.
Blood tests may show anaemia, high globulins, low albumin or other inflammatory changes, but none is diagnostic alone. Ultrasound can identify effusions, enlarged lymph nodes or organ lesions. When fluid is present, its appearance, protein content, cell population and specialised tests can make FIP much more or less likely.
PCR or antigen testing is most informative when performed on appropriate effusion or affected tissue and interpreted with cytology or histopathology. A positive faecal coronavirus PCR mainly shows intestinal shedding and should not be presented as proof of FIP.
Because effective antiviral treatment works best when started promptly, a veterinarian may recommend treatment when the accumulated evidence makes FIP very likely even if invasive biopsy is not safe or practical. Rapid deterioration, neurological signs or breathing difficulty increases the urgency of specialist assessment.
A positive feline coronavirus antibody or faecal PCR does not diagnose FIP because exposure to ordinary enteric coronavirus is common. Diagnosis is based on the whole pattern: clinical signs, blood changes, imaging, analysis of any effusion and, where appropriate, detection of coronavirus within affected cells or tissues. Delaying assessment based on outdated expectations can deny a treatable cat its best chance of recovery.
Treatment & Management
Current treatment centres on effective antiviral therapy, most commonly oral GS-441524 or a related nucleoside analogue under veterinary supervision. Protocols vary according to the cat’s clinical form, neurological or ocular involvement, product availability and local regulation. Very sick cats that cannot initially take oral medication may receive an injectable antiviral such as remdesivir where available.
Supportive treatment is tailored to the cat and may include fluids, anti-nausea medication, pain relief, nutritional support and management of anaemia or effusions. Cats often improve noticeably within days when antiviral treatment is effective, but the full course must be completed and dosing adjusted as body weight changes.
Monitoring includes weight, temperature, appetite, clinical signs and repeat blood testing. Cats with ocular or neurological disease often require particularly careful follow-up. Unregulated products of uncertain composition should be avoided when a veterinary-supplied or legally compounded option is available.
Most cats that respond well can return to a good quality of life, and relapse is much less common when an appropriate course is completed. Preventive management focuses on reducing coronavirus transmission pressure in multi-cat environments through hygiene, litter management and avoiding overcrowding. FIP vaccination is not routinely recommended in current international feline vaccination guidelines.
Breeds or species affected
Abyssinian
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American Bobtail
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American Curl
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American Shorthair
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American Wirehair
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Arabian Mau
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Aegean
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Australian Mist
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Balinese
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Bengal
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Birman
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Bombay
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British Longhair
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British Shorthair
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Burmese
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Burmilla
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Chartreux
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Chausie
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Colorpoint Shorthair
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Cornish Rex
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Cymric
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Devon Rex
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Domestic Longhair
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Domestic Medium Hair
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Domestic Shorthair
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Donskoy
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Egyptian Mau
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European Shorthair
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Exotic Shorthair
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Havana Brown
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Highlander
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Himalayan
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Japanese Bobtail
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Khao Manee
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Korat
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Kurilian Bobtail
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LaPerm
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Lykoi
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Maine Coon
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Manx
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Minuet
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Minskin
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Munchkin
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Nebelung
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Norwegian Forest Cat
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Ocicat
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Oriental Longhair
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Oriental Shorthair
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Persian
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Peterbald
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Pixiebob
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RagaMuffin
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Ragdoll
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Russian Blue
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Savannah
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Scottish Fold
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Scottish Straight
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Selkirk Rex
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Siamese
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Siberian
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Singapura
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Snowshoe
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Somali
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Sphynx
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Thai
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Tonkinese
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Toybob
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Toyger
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Turkish Angora
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Turkish Van
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Bambino
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Cheetoh
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Dwelf
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Elf Cat
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Genetta
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Kinkalow
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Lambkin
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Serengeti
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Skookum
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Ukrainian Levkoy
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