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Feline Enteric Coronavirus |  |
| Feline enteric coronavirus is an enveloped single-stranded RNA virus that is highly contagious among cats in close contact. Although the feline enteric coronavirus is antigenically similar to the virus of feline infectious peritonitis (FIP,
Feline Infectious Peritonitis and Pleuritis: Introduction), the pathogenesis of each differs. The enteric form of infection is limited to the GI tract. Death from the enteric form of disease is uncommon. |
| Etiology and Pathophysiology: |
| The virus is shed in the feces of seropositive cats. Close contact between cats is required for effective transmission, although the possibility of transmission via fomites also exists. The close antigenic relationship of the enteric form of the virus and that causing clinical signs of FIP has led to speculation that FIP virus may be a mutated form of enteric coronavirus. Cross-protection is not induced by either virus to the other, and recent evidence refutes the supposition
that preexisting infection with the enteric form of disease accelerates or enhances the severity of disease associated with FIP. |
| Feline coronavirus infects the apical columnar epithelium of intestinal villi of the duodenum, jejunum, and ileum, and causes the tips of villi to slough, fuse with adjacent villi, and atrophy. |
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| Clinical Findings: |
| In catteries, the virus may be a cause of inapparent to mildly severe enteritis in kittens 6-12 wk old. Recently weaned kittens may exhibit fever, vomiting, and diarrhea that may last 2-5 days. More severely affected kittens may also be anorectic for 1-3 days. Adult cats often have subclinical infection. Transient neutropenia may appear with the onset of diarrhea in more severely affected kittens. |
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| Diagnosis: |
| Most FIP infections result in seroconversion without progression to the fatal form of the disease. Positive coronavirus antibody titers are seen in ~10-40% of cats in the general cat population and in 80-90% of cats in catteries, but only 8% develop FIP. Serologic tests (serum ELISA and immunofluorescent antibody) do not differentiate the enteric form of the virus from that causing clinical signs associated with FIP. Furthermore, these tests do not differentiate between past
exposure to the virus or an actively infected cat. Titers >1:3,200 are suggestive of FIP, as opposed to the enteric form of disease. Titers between 1:100 and 1:3,200 may be found in cats with effusive or noneffusive disease and in cats with the enteric form. Some commercial vaccines containing bovine serum components may induce antibody production that may react with antigenically similar bovine serum components in cell cultures used to propagate target FIP viruses for
immunochemical tests, thus causing a false-positive test in recently vaccinated (<4 mo previously) cats. Consequently, antibody testing is only useful as a screening tool to detect the presence or absence of virus in a household, to recognize potential carriers or shedders when introducing new cats into an antibody-negative population, and as an aid in the clinical diagnosis of FIP. |
| Cytologic evaluation of effusions from cats with the wet form of FIP have a high protein content and a variable cell count consisting of neutrophils, macrophages, and lymphocytes. The neutrophils are nondegenerate and do not show signs of toxicity, and the lymphocytes are morphologically normal. |
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| Treatment and Control: |
| The virus is ubiquitous in cats, and many cats that recover from the infection remain carriers. Enteric coronavirus infection can be prevented only by minimizing exposure to infected cats and their feces. Cats with the enteric disease do not progress to develop clinical signs of FIP. Most cats develop an effective immune response on exposure and recover from infection. However, once clinical signs of disease develop in cats with FIP, the disease is invariably fatal. Management
consists only of supportive therapy, ie, fluids when indicated. Vaccination with the temperature-sensitive intranasal vaccine for FIP may protect against challenge with virulent enteric coronavirus. |
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