Feline Herpes Virus

Feline herpes virus (FHV-1, feline viral rhinotracheitis) is caused by a virus in the family Herpesviridae and the genus Vericellovirus (subfamily Alphaherpesvirinae).  FHV-1 is an enveloped virus with an icosohedral capsid that is 150 to 200 nm in diameter and contains a linear double-stranded DNA genome (3). FHV-1 is found worldwide and can infect members of the family Felidae of any breed or age, however kittens, immunosuppressed cats, cats infected with feline T-cell leukemia virus or feline immunodeficiency virus, or cats under stress or with poor nutrition are more susceptible.  The virus was first identified in 1957 and is one of two viruses that cause acute respiratory disease of kittens (the other is calcivirus); about half of all kittens with acute respiratory disease have FHV-1 (1).  Transmission is via contact with infected materials either by direct contact, contact with infected fomites, or via respiratory droplets.   It is known that the sneeze of FHV-1 infected cats can spread the virus up to 4 feet.  It is thought that most  cats (~70%) develop FHV-1 infections at an early age.  Due to poor immune responses, cats can suffer multiple infections, and this virus is a problem in animal care facilities and catteries that house many cats in high density. 

Most infections are mild, causing nasal discharge, swelling of the conjunctiva of the eye (Fig. 1), and sneezing, coughing, fever, and anorexia beginning 2 to 5 days after exposure.  However, in some cats, the virus can infect the eye causing blindness (Fig. 2 and 3).  Oral lesions are also often noted (Fig. 4 and 5) but are more common in calcivirus infections (1).   In young kittens and senior cats, pneumonia (Fig. 6 and 7) may result in death.  Mortality may reach as high as 30% in young kittens and older cats.  Pregnant females may abort their fetuses. Like all herpes viruses, the viruses' ability to establish a lifelong latent state causes some cats to become latent asymptomatic shedders of the virus, probably serving as a reservoir for infection of other cats. Cats are known to increase shedding when under stress.  All cats that recover from these infections should be considered potential carriers (2).  There is a vaccine available; however, it reduces disease but does not prevent infection (1). 

3.  Roizman, R., and P. E. Pellet. 2001.  The family Herpesviridae: a brief introduction, p. 1679–1728. InD. M. Knipe and P. M. Howley (ed.), Fields virology.  Lippincott Williams and Wilkins, Philadelphia, Pa.