Feline infectious peritonitis (FIP) virus

Test code: S0096 - Qualitative detection of FIPV by reverse transcription coupled real time polymerase chain reaction

Feline infectious peritonitis (FIP) is caused by a coronavirus that can infect any cat, but especially young cats and very old cats (14 yr and up). The FIP virus (FIPV) is genetically very similar to another coronavirus, feline enteric corona virus (FECV), which causes a transient, usually mild, self-limiting diarrhea. In fact, there is evidence that FECV can mutate to FIPV in some individuals.

Many apparently healthy cats carry the FIP virus, shedding it intermittently in bodily fluids or feces. Interestingly, mortality from environmental exposure to the virus (ie from other animals shedding FIP virus) is sporadic, even in a population of cats where FIP virus carriers are known to be present. This is most likely due to the primarily mutational mechanism of acquired FIP.

Clinical development of the disease is quite complex and, depending on the status of the animal’s immune system, symptoms can vary significantly. In some instances, the immune system’s response to infection may actually worsen clinical signs. Two major forms of the disease can be recognized. In the effusive form of the disease there is accumulation of substantial quantities of fluid in body cavities (abdomen and chest). Some of these animals appear profoundly "pot-bellied". In the dry form of the disease there is little fluid buildup. In both forms, clinical signs can be quite variable; virtually any organ or soft tissue system can become affected, thus mimicking many diseases. The most common clinical signs are non-specific and include fluctuating fever, inappetance, lethargy and weight loss. Sometimes, if the central nervous system is affected, neurological abnormalities are apparent.

In the past, diagnosis of active FIP was based on a high level of antibody to the FIP virus along with signs of the disease which may or may not be specific. Recent research indicates that serology testing yields many false negative and false positive results (Addie, 2004). There are several reasons for this. First, FIPV and FECV are extremely similar and hence exhibit strong serologic cross reactivity; in fact cats exposed to other feline coronaviruses may test "positive" or even "strongly positive” for FIPV by serology. Second, FIPV vaccination may cause uninfected cats to test positive by serology. Third, some FIPV-infected cats simply may not develop an immune response. Immune system components may actually be involved in the progression of the disease and be "consumed" in the disease process. Or, the disease may be in the early stages so that there has not yet been enough time to develop the antibodies. Also, some animals are immune-suppressed from concurrent diseases such as feline AIDS, so that the immune response machinery is destroyed. Finally, antibody levels fluctuate up and down, seemingly in random fashion, in both FIPV and FECV infected cats. No specific pattern has been discernable in this fluctuation, so a change in antibody titer does not imply an active infection.

Detection of FIPV by reverse transcription polymerase chain reaction is currently regarded as the most specific and sensitive technique for detecting FIPV (Kennedy, 2003). Recent research indicates that reverse transcription PCR detection of FIPV in blood is highly predictive of active infection. Since this technique directly detects the viral nucleic acid, a positive result provides a strong indication of the presence of the virus.

Utilities:

• Confirm the disease causing agent
• Shorten the time required to confirm a clinical diagnosis of FIPV infection
• Ensure that feline populations are free of FIPV
• Early prevention of spread of this virus among a population
• Minimize personnel exposure to this virus

References:
Addie, D.D., McLachlan, S.A., Golder, M., Ramsey, I., Jarrett, O. (2004) Evaluation of an in-practice test for feline coronavirus antibodies. J Feline Med Surg. Apr 6(2):63-7.
Kennedy, M., Kania, S., Stylianides, E., Bertschinger, H., Keet, D., van Vuuren, M. (2003) Detection of feline corona virus infection in southern African non domestic felids. J Wildlife Dis. Jul 39(3):529-35.

Specimen requirement: 0.5 ml whole blood in EDTA (purple top) or ACD (yellow top) tube.

For specimen types other than those listed here, please call to confirm specimen acceptability and shipping instructions.

For all specimen types, if there will be a delay in shipping, or during very warm weather, refrigerate specimens until shipped and ship with a cold pack unless more stringent shipping requirements are specified. Frozen specimens should be shipped so as to remain frozen in transit. See shipping instructions for more information.

Turnaround time: 2 business days

Methodology: Qualitative reverse transcription coupled real time PCR

Normal range: Nondetected