Feline calicivirus
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Feline calicivirus (FCV) is a virus of the family Caliciviridae that causes disease in cats. It is one of the two important viral causes of respiratory infection in cats. FCV can be isolated from about 50 percent of cats with upper respiratory infection.[1] Cheetahs are the other species of the family Felidae known to become infected naturally.[1] There are different strains of FCV that vary in virulence. FCV is secreted in saliva, feces, urine, and respiratory secretions and can be transmitted through the air and orally. Infected cats usually shed the virus for two weeks but may develop latent infection and shed for life.[2] Coinfection with either feline herpesvirus or feline immunodeficiency virus causes a more severe disease.
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[edit] Symptoms
Symptoms in cats infected with FCV may develop acutely, chronically, or not at all. Latent or subclinical infections often become symptomatic when the cat is stressed, such as at the time of adoption. Acute symptoms of FCV include fever, conjunctivitis, nasal discharge, sneezing, and ulceration of the mouth (stomatitis). Pneumonia may develop with secondary bacterial infections. In addition to stomatitis, some cats may develop a polyarthritis, both probably immune-mediated through immune complex deposition. Stomatitis and polyarthritis can develop without any upper respiratory infection symptoms, but fever and loss of appetite may occur. Less commonly, glomerulonephritis can develop in chronic cases secondary to immune complex deposition.
An antigenically different form of FCV has been found to cause a severe systemic disease in cats, similar to rabbit hemorrhagic disease (which is also caused by a calicivirus). This virus has been called virulent systemic feline calicivirus (VS-FCV). VS-FCV can cause a rapid epidemic with a mortality rate of up to 67 percent.[2] Symptoms include fever, edema of the limbs and face, and multiple organ dysfunction syndrome. The disease is caused by direct viral invasion of epithelium and endothelium and secondary host immune response.
Diagnosis of FCV is difficult without specific tests because the symptoms are similar to other feline respiratory diseases, especially feline viral rhinotracheitis. The presence of stomatitis may indicate FCV. Specific tests include virus culture, polymerase chain reaction (PCR), and immunohistochemical staining.
[edit] Treatment and prevention
There is no specific treatment for FCV. Antibiotics are used for secondary bacterial infections. Nursing care and rehydration are used for dehydrated and anorexic cats. Corticosteroids or azathioprine may be used for polyarthritis. Stomatitis is very difficult to treat. Antibiotics, corticosteroids, and tooth extractions all have been used with varying success. Cats on corticosteroids must be monitored carefully for worsening of any upper respiratory infection.
Natural immunity from maternal antibodies lasts in the kitten from three to nine weeks.[2] After that, kittens are susceptible to FCV. Previous infection does not guarantee lifelong immunity, since an antigenically dissimilar FCV can cause infection. However, usually after the age of three years FCV infections are mild or asymptomatic.[2] FCV vaccination will not always prevent disease but will reduce the severity. FCV vaccines come in two types, attenuated (live, but not virulent) and inactivated. Attenuated FCV vaccine has been shown to possibly cause mild upper respiratory infection. Inactivated vaccine does not, but it causes more local inflammation and possibly predisposes the cat to vaccine-associated sarcoma.[2]
Quarantine is best for control of FCV in catteries and kennels. However, FCV is very contagious and latently infected cats will continue to shed virus, so complete control is difficult.
[edit] References
- ^ a b Fenner, Frank J.; Gibbs, E. Paul J.; Murphy, Frederick A.; Rott, Rudolph; Studdert, Michael J.; White, David O. (1993). Veterinary Virology (2nd ed.). Academic Press, Inc. ISBN 0-12-253056-X.
- ^ a b c d e Foley, Janet E. (2005). “Calicivirus: Spectrum of Disease”, August, John R. (ed.): Consultations in Feline Internal Medicine Vol. 5. Elsevier Saunders. ISBN 0-7216-0423-4.
