FIP, Deadly Killer to Cats

Cat with Feline infectious peritonitisFeline infectious peritonitis (FIP) is one of the most complex infectious diseases and is one of the worst diseases imaginable.  It is caused by a mutation of the Corona virus.   Similar viruses you may be familiar with include Ebola virus, influenza, AIDS and rhinoviruses.  Coronaviruses can cause disease in almost every animal species but overall are species specific: feline coronaviruses do not infect humans.

Feline Enteric Coronavirus  normally stays in the intestinal tract, infecting the top layer of the cells lining the small intestine before settling in the colon. FECV may cause mild diarrhea and vomiting but is not considered a serious pathogen.

An FECV-infected cat may shed large numbers of virus and shedding may continue for months.  Immunity to FECV is usually temporary and previously immune animals can be reinfected. This is one of the reasons that prevention by vaccine is difficult to impossible.

Specific mutations in the FECV virus allow it to leave the intestinal tract where it infects immune system cells that normally help fight infection. This mutated version of FECV is referred to as FIPV. Infected macrophages spread the disease throughout the cat’s body.  The exact mutation can be unique to each cat.  FIPV is not transmitted to other cats; transmission occurs via the unmutated FECV.

FIP is a disease associated with high density cat populations. Kittens are most susceptible to developing FIP and typically become infected with FECV at around 9 weeks of age. Worldwide, FIP can occur in dense urban or rural populations of free roaming cats. In the US, it is more common to see FIP in cats and kittens from high density conventional shelters and kitten/foster/rescue groups where kittens may be exposed to massive amounts of virus.  The other source of FIP is pedigree catteries.

FIP is on the rise probably due to increasing numbers of rescue operations where kittens may be bottle-fed, weaned early, and exposed to large amounts of FECV virus.

FIP is often categorized into dry and effusive (wet) forms but there can be mixtures and switches between types. In general, the effusive form, characterized by internal fluid secretions resulting in a swelling abdomen or fluid in the lungs along with other symptoms, has a rapid course and may kill a cat quickly.  The dry form may persist for months to about a year, sometimes longer.

Feline infectious peritonitis imageWet Form Feline infectious peritonitis imageDry Form

Risk factors for developing FIP include the prevalence of cats that are FECV shedders, the magnitude of virus shedding, number of cats in the 4 to 29-month-old age range, and genetic predisposition. Often FIP appears in young cats following a stressful event, such as neutering or spaying.

Older cats may also develop FIP. A typical history is that one (or more) cats in a multicat household die of old age and the owner feels that a remaining cat needs a new buddy and so gets a kitten from a rescue facility. The older cat lost immunity to FECV years before and now is susceptible to infection. Because of age, the older cat may have poorer immune responses than a younger animal and may be more likely to develop FIP.

Senior cat

Traditional treatments do not work. Immunosuppressants such as corticosteroids may make the cat feel better but ultimately does not alter the course of the disease. Biologics do not work. Vaccines do not work because the kitten is usually infected with FECV before vaccination and because immunity is transient. The most common cause of death for felines with FIP is euthanasia, due to the loss of quality of life as the disease inevitably progresses. Although the effusive form of FIP is often rapidly fatal, some cats can live longer than one might imagine (weeks or months) with supportive care. Pulmonary fluids need to be drained, but abdominal fluids typically should not be drained. Cats with the dry form may stay alive for months or more. Some spontaneous remissions can occur, but usually all cats ultimately succumb to FIP.

Hope may come in the form of newer antiviral drugs.  Although the studies are promising, there remain many unanswered questions.

If you suspect your cat or kitten has FIP or for more information on FIP please contact Meadowlands Veterinary Hospital at 201-646-2008 or visit us at


By |April 12th, 2019|
Font Resize