Feline viral rhinotracheitis (FVR) is an upper respiratory infection of cats caused by feline herpesvirus 1, of the family Herpesviridae. It is also known as feline influenza and feline coryza. Viral respiratory diseases in cats can be serious, especially in catteries and kennels. Causing one-half of the respiratory diseases in cats,Ã‚Â FVR is the most important of these diseases and is found worldwide. The other important cause of feline respiratory disease is feline calicivirus.
FVR is very contagious and can cause severe disease, including death from pneumonia in young kittens. All members of the Felidae family are susceptible to FVR, in fact FHV-1 has caused a fatal encephalitis in lions in Germany.
Initial symptoms of FVR include coughing, sneezing, nasal discharge, conjunctivitis, and sometimes fever and loss of appetite. The symptoms usually resolve within four to seven days, but secondary bacterial infections can cause persistence of symptoms for weeks.Ã‚Â Frontal sinusitis and empyema can also result.
FHV-1 also has a predilection for corneal epithelium, resulting in corneal ulcers, often pinpoint or dendritic in shape. Other ocular symptoms of FHV-1 infection include conjunctivitis, keratitis, keratoconjunctivitis sicca (decreased tear production), and corneal sequestra. Infection of the nasolacrimal duct can result in chronic epiphora (excess tearing). Ulcerative skin disease can also result from FHV-1 infection.Ã‚Â FHV-1 can also cause abortion in pregnant queens, usually at the sixth week of gestation,Ã‚Â although this may be due to systemic effects of the infection rather than the virus directly.
In chronic nasal and sinus disease of cats, FHV-1 may play more of an initiating role than an ongoing cause. Infection at an early age may permanently damage nasal and sinus tissue, causing a disruption of ciliary clearance of mucus and bacteria, and predispose these cats to chronic bacterial infections.
Diagnosis of FVR is usually by the symptoms, especially corneal ulceration. Definitive diagnosis can be done by direct immunofluorescence or virus isolation. However, many healthy cats carry feline herpes virus asymptomatically, so a positive test for FHV-1 does not necessarily indicate that symptoms of an upper respiratory tract infection are due to it. Early in the course of the disease, histological analysis of cells from the tonsils, nasal tissue, or nictitating membrane (third eyelid) may show inclusion bodies (a collection of viral particles) within the nucleus of infected cells.