Feline infectious peritonitis
Encyclopedia
Feline infectious peritonitis (FIP) is a fatal incurable disease that affects cat
Cat
The cat , also known as the domestic cat or housecat to distinguish it from other felids and felines, is a small, usually furry, domesticated, carnivorous mammal that is valued by humans for its companionship and for its ability to hunt vermin and household pests...

s. It is believed by some to be caused by Feline Infectious Peritonitis Virus (FIPV), which is a mutation of Feline Enteric Coronavirus
Coronavirus
Coronaviruses are species in the genera of virus belonging to the subfamily Coronavirinae in the family Coronaviridae. Coronaviruses are enveloped viruses with a positive-sense single-stranded RNA genome and a helical symmetry. The genomic size of coronaviruses ranges from approximately 16 to 31...

 (FECV) - (Feline Coronavirus FeCoV). Although there appears to be a connection between FIP and feline coronavirus, no clear cause and effect has yet been proven. Experts do not always agree on the specifics of FIP. However, the most common theory is that the normally benign FECV mutates into FIPV. The mutated virus has the ability to invade and grow in certain white blood cell
White blood cell
White blood cells, or leukocytes , are cells of the immune system involved in defending the body against both infectious disease and foreign materials. Five different and diverse types of leukocytes exist, but they are all produced and derived from a multipotent cell in the bone marrow known as a...

s, namely macrophages. The immune system's response causes an intense inflammatory reaction
Inflammation
Inflammation is part of the complex biological response of vascular tissues to harmful stimuli, such as pathogens, damaged cells, or irritants. Inflammation is a protective attempt by the organism to remove the injurious stimuli and to initiate the healing process...

 in the containing tissues. This disease is generally fatal http://www.vet.cornell.edu/fhc/brochures/fip.html. However, its incidence rate is roughly 1 in 5000 for households with one or two cats. A nasally administered vaccine for FIP is available, but controversial and isn't proven to be highly effective. http://www.vetinfo.com/cencyclopedia/cefip.html. Great strides are being made with an experimental polyprenyl immunostimulant being manufactered by Sass and Sass and tested by Dr. Al Legendre. In one case study, a female cat diagnosed with dry FIP has survived 26 months from the date of definitive diagnosis (Fall 2009).

See also the special article about Feline Coronavirus

Transmission and infection

FECV is very common, especially in places where large groups of cats are kept together (animal shelter
Animal shelter
An animal shelter is a facility that houses homeless, lost, or abandoned animals; primarily a large variety of dogs and cats.Parrots, for example, are the third most common pet owned by people...

s, catteries, etc). Cats become infected by inhaling or ingesting the virus. The most commonly cited transmission source is feces, although contaminated surfaces such as food dishes and clothing can transmit the virus as well.

Despite the prevalence of FECV, most infected cats do not develop FIP. Often, exposure to FECV produces no clinical signs, but may cause a mild diarrhea
Diarrhea
Diarrhea , also spelled diarrhoea, is the condition of having three or more loose or liquid bowel movements per day. It is a common cause of death in developing countries and the second most common cause of infant deaths worldwide. The loss of fluids through diarrhea can cause dehydration and...

. Therefore, a cat without clinical signs may still be an FECV carrier and may pass the virus to another cat. In any cat infected with FECV there is a chance that the virus may mutate into the FIP causing form. This chance is increased for cats that are immune compromised including very young and very old cats. There is also thought to be a genetic component to susceptibility to viral mutation.

Signs

There are two main forms of FIP: effusive (wet) and non-effusive (dry). While both types are fatal, the effusive form is more common (60-70% of all cases are wet) and progresses more rapidly than the non-effusive form.

Effusive (wet)

The hallmark clinical sign of effusive FIP is the accumulation of fluid within the abdomen or chest, which can cause breathing difficulties. Other symptoms include lack of appetite, fever, weight loss, jaundice
Jaundice
Jaundice is a yellowish pigmentation of the skin, the conjunctival membranes over the sclerae , and other mucous membranes caused by hyperbilirubinemia . This hyperbilirubinemia subsequently causes increased levels of bilirubin in the extracellular fluid...

, and diarrhea.

Non-effusive (dry)

Dry FIP will also present with lack of appetite, fever, jaundice, diarrhea, and weight loss, but there will not be an accumulation of fluid. Typically a cat with dry FIP will show ocular
Eye
Eyes are organs that detect light and convert it into electro-chemical impulses in neurons. The simplest photoreceptors in conscious vision connect light to movement...

 or neurological
Neurology
Neurology is a medical specialty dealing with disorders of the nervous system. Specifically, it deals with the diagnosis and treatment of all categories of disease involving the central, peripheral, and autonomic nervous systems, including their coverings, blood vessels, and all effector tissue,...

 signs. For example, the cat may develop difficulty in standing up or walking, becoming functionally paralyzed over time. Loss of vision is another possible outcome of the disease.

Diagnosis

The signs associated with FIP are often non-specific, which can cause diagnosis to be very difficult. There is as yet no definitive diagnostic test for FIP. Diagnosis may include a combination strong clinical suspicion, physical examination findings, presence of abdominal fluid with characteristic chemistry changes and examination of affected tissues for the FIP virus (this is usually performed post-mortem, but can be performed via tissue biopsy). Histopathological
Histopathology
Histopathology refers to the microscopic examination of tissue in order to study the manifestations of disease...

 examination of tissue samples is usually the cheapest available diagnostic test, but its sensitivity and specificity for FIP is questionable. A polymerase chain reaction
Polymerase chain reaction
The polymerase chain reaction is a scientific technique in molecular biology to amplify a single or a few copies of a piece of DNA across several orders of magnitude, generating thousands to millions of copies of a particular DNA sequence....

 test is also available for use with fluid or certain tissue samples; however, its efficacy is currently being reviewed.

More commonly, a presumptive diagnosis is made based on clinical signs and evaluation of abdominal or chest fluid, if available. Fluid caused by FIP tends to be yellow in color and have elevated protein levels. Blood tests can also be performed to bolster a presumptive diagnosis by looking for coronavirus antibodies and elevated protein. Coronavirus titer
Titer
A titer is a way of expressing concentration. Titer testing employs serial dilution to obtain approximate quantitative information from an analytical procedure that inherently only evaluates as positive or negative. The titer corresponds to the highest dilution factor that still yields a positive...

s are NOT considered diagnostic in and of themselves due to the ubiquity of FeCoV, but may be used in conjunction with clinical symptoms to make an FIP diagnosis. It is important to note that cats with higher titres of FCoV are no more likely to develop FIP than those with lower titres.

In the presence of abdominal or chest fluid, a simple test called Rivalta test
Rivalta test
Rivalta test is used in order to differentiate a transudate from an exudate.A test tube is filled with distilled water and acetic acid is added. To this mixture one drop of the effusion to be tested is added. If the drop dissipates, the test is negative, indicating a transudate...

 can be used to differentiate fluid resulting from FIP from fluids resulting from some other disease with very good accuracy.

Treatment

Accepted wisdom is that there is no cure for FIP; treatment is symptomatic and palliative
Palliative care
Palliative care is a specialized area of healthcare that focuses on relieving and preventing the suffering of patients...

 only, i.e. typically the owner is advised to make the cat as comfortable as possible. Prednisone
Prednisone
Prednisone is a synthetic corticosteroid drug that is particularly effective as an immunosuppressant drug. It is used to treat certain inflammatory diseases and some types of cancer, but has significant adverse effects...

 or other immunosuppressive drugs prescribed by a veterinarian may help to prolong the cat's life for a few weeks or months, but may be contraindicated in certain cases due to concomitant infection(s), although this risk can be mitigated somewhat by also treating with antibiotics. Newer approaches using immune modulators are being developed by several companies.

Effusive FIP usually progresses too rapidly for any meaningful therapy to be attempted.

Quarantine is not necessary as FIP is not truly an infectious disease. Feline Enteric Coronavirus is shed in the feces and can be passed on to other cats, however, it is the mutated form of the virus that leads to FIP. This form is only found in macrophages and is therefore not shed and not contagious.

As FIP signs can be easily overlooked, it is highly advised to have your cat examined by your family veterinarian at any signs of abdominal distention, changes in the eyes, chronic diarrhea, unusual lethargy or respiratory infection. While treatment will only be symptomatic, it may prolong the life of the cat as well as soften the blow to the owner. FIP patients can benefit from cytotoxic drugs such as methotrexate and cytoxan, and from corticosteroids such as methylprednisone or prednisolone; although it is not a cure, it often improves appetite and weight, and can make the cat less lethargic. In some cases, cytotoxic drugs can induce a brief remission, and even corticosteroids alone can give the cat 3-5 more months of good quality life. In spite of these treatments, however, prognosis remains extremely poor.

External links

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