D3372 - Feline Coronavirus (Feline infectious peritonitis)

Description:

Feline infectious peritonitis (FIP) is a fatal, immunemediated, pyogranuloma-tous disease of domestic and wild cats. The causative agent, FIP virus (FIPV), is a member of the family Coronaviridae, a group of enveloped, positive-stranded RNA viruses. Feline coronaviruses differ widely in their pathogenic potentials. Some isolates cause Feline infectious peritonitis in virtually 100% of experimentally infected cats, while others produce mild enteric infections. These avirulent isolates are commonly referred to as feline enteric coronaviruses (FeCVs). The key pathogenic event in FIP is the infection of monocytes and macrophages. Avirulent FeCV is thought to remain confined to the digestive tract and not to spread beyond the intestinal epithelium and regional lymph nodes. FIPV, however, disseminates to other organs, most likely via blood-borne monocytes. FeCV is found frequently in cats: antibodies are present in 80 to 90% of the cats in catteries and in 10 to 50% of those in single-cat households. Because only 5 to 10% of seropositive cats die of Feline infectious peritonitis, it is believed that most cats become infected with avirulent FeCV strains. However, factors such as the susceptibility and age of the host, stress on the host, and virus dose clearly influence the outcome of an infection with virulent feline coronaviruses; a large proportion of healthy seropositive cats may in fact have experienced a sublethal infection with FIPV. There is circumstantial evidence for the occurrence of healthy, asymptomatic carriers.
Feline infectious peritonitis is often misdiagnosed as its general signs-chronic fever, weight loss, anorexia, and malaise-are nonspecific. In classical ‘‘wet’’ or ‘‘effusive’’ FIP, these signs are accompanied by a gradual abdominal distension with a viscous yellow ascitic fluid. Another form of Feline infectious peritonitis, in which little or no exudate is present, occurs. This so-called ‘‘dry’’ or ‘‘noneffusive’’ FIP is difficult to recognize. The ocular and neurologic problems frequently seen in cats with noneffusive FIP are also observed with other conditions of bacterial and viral origin. The clinicopathological changes in Feline infectious peritonitis (lymphopenia, neutrophilia, anemia, hyperproteinemia, and hypergamma-globulinemia) are nonspecific and not helpful in making a differential diagnosis.

Diagnosis:

Serology is extensively used as a diagnostic tool: rising or high titers (>400), as measured by immunofluorescence, are assumed to be indicative of Feline infectious peritonitis. However, in view of the facts that a large percentage of the healthy cat population is FeCV seropositive and that high antibody titers are frequently found in asymptomatic cats, the data from coronavirus serology must be interpreted with care. At present, a definite diagnosis of FIP can be established only by histopathologic examination of biopsy or postmortem material.
Compared with serology, reverse transcriptase PCR (RT-PCR) provides the obvious advantage of directly detecting an ongoing infection rather than documenting a previous immune system encounter with a coronavirus. The target for PCR test is a segment of the gene coding for peplomer protein E2. This gene was chosen because there is known antigenic difference in the E2 protein between FIPV and FeCV which may be due to differences in the RNA sequences of the E2 genes. Preliminary evaluation of the PCR assay for the detection of viral nucleic acid in cats with Feline infectious peritonitis disease demonstrated that the assay has good sensitivity and specificity. On the basis of clinical laboratory and histopathologic criteria, the preliminary sensitivity and specificity of the assay were 92% and 94%, respectively. The PCR test can detect a single virus sequence in approximately 70,000 monocytes and macrophages. The diagnostic test based on detection of viral nucleic acid by PCR is reasonably reliable for determining active FIPV infection.

Sample:

1. Whole blood (3 ml) in a lavender top (EDTA) tube.
2. Stool sample submitted in a sterile container.
3. Abdominal fluid in a red top tube.

Special Handling:

Store blood sample and swab at 4°C until pick up or shipment.

Test Code:

D3372

1. Gamble et al. (1997) Development of a nested PCR assay for detection of feline infectious peritonitis virus in clinical specimens. J.Clin. Microbiol. 35: 673-675.
2. Herrewegh et al. (1995) Detection of feline coronavirus RNA in feces, tissues, and body fluids of naturally infected cats by reverse transcriptase PCR. J. Clin. Microbiol. 33: 684-689.