or feline immunodeficiency virus causes a more severe disease. Clinical signs Clinical signs in cats infected with FCV may develop acutely, chronically, or not at all. Latent or subclinical infections often become clinical when the cat is stressed, such as at the time of adoption. Acute signs 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 signs, but fever and loss of appetite may occur. Less commonly, glomerulonephritis can develop in chronic cases secondary to immune complex deposition. The great variability of clinical signs in individual cases of FCV is related to the relative virulence of different strains of the virus. VS-FCV can cause a rapid epidemic, with a mortality rate of up to 67%. Initial clinical signs include discharge from the eyes and nose, ulceration in the mouth, anorexia, and lethargy, and occur in the first one to five days. Later signs include fever, edema of the limbs and face, jaundice, and multiple organ dysfunction syndrome. Diagnosis of FCV is difficult without specific tests, because the signs 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, and immunohistochemical staining. Treatment and prevention There is no specific treatment for FCV. Antibiotics are used for secondary bacterial infections, and immune modulators, such as lymphocyte T-cell immune modulator, have been used for immune support. 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. After that, kittens are susceptible to FCV. Previous infection does not guarantee lifelong immunity, since an antigenically dissimilar FCV (such as VS-FCV) can cause infection. However, usually after the age of three years, FCV infections are mild or asymptomatic. FCV vaccination will not always prevent disease, but can reduce the severity. FCV vaccines come in two types, inactivated (ATCvet code: ) and attenuated (live, but not virulent;