Feline infectious peritonitis (FIP) virus and feline enteric coronavirus (FECV, aka FCoV)

Test codes:

S0096 - Qualitative detection of FIP virus by reverse transcription coupled real time polymerase chain reaction.

S0108 - Qualitative detection of FECV 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. FECV infection often persists in apparently healthy animals,which shed the virus in their feces. Natural infection occurs via the faecal-oral route. FECV infection appears to be mainly restricted to the intestinal tract (Chang, 2010; Vogel, 2010), where the virus replicates in villous epithelial cells (Vogel, 2010).

Unlike FECV, FIPV does not spread readily among cats. Instead, it originates de novo from FECV in individual animals (Vogel, 2010). Clinical development of FIP 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 FIP 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 FIP 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.

Many apparently healthy cats carry the FECV virus, shedding it intermittently in feces. Mortality from environmental exposure to FECV virus (ie from other animals shedding virus) is sporadic, even in a population of cats where FIP virus carriers are known to be present. Additionally, most cats with FIP no longer have detectable intestinal feline coronaviruses (Chang, 2010).

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. However, serology testing can yield 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 impaired. 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.

In live cats, detection of FIPV by reverse transcription polymerase chain reaction is regarded as a relatively specific and sensitive technique for detecting FIPV (Kennedy, 2003). Recent research indicates that reverse transcription PCR detection of FIPV in mesenteric lymph node fine needle aspirate samples or thoracic effusion samples is 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 systemic (FIP) virus. In view of the low rate of false positive results, reverse transription coupled real time PCR can be a valuable addition to the diagnostic arsenal for FIP (Simons, 2005).

Utilities:

• Help confirm the disease causing agent
• Differentiate between these and other coronaviruses
• Shorten the time required to confirm a clinical diagnosis of FIP infection
• Help ensure that feline collections or populations are free of FeCV and FIP
• Early prevention of spread of these viruses among a collection or population
• Minimize human exposure to these viruses

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.
Chang, H.W. et al (2010) Feline infectious peritonitis: insights into feline coronavirus pathobiogenesis and epidemiology based on genetic analysis of the viral 3c gene. Journal of General Virology. 91, 415–420.
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.
Simons, F.A et al (2005) A mRNA PCR for the diagnosis of feline infectious peritonitis. J Virol Methods 124(1-2):111-6.
Vogel, L. et al (2010) Pathogenic characteristics of persistent feline enteric coronavirus infection in cats. Vet. Res. 41:71.

Specimen requirements:
FIP: 0.1 ml mesenteric lymph node fine needle aspirate, or 0.2 ml thoracic effusion
FECV: 0.2 ml feces, or rectal swab

Contact Zoologix if advice is needed to determine an appropriate specimen type for a specific diagnostic application. For specimen types not listed here, please contact Zoologix 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