Feline Herpesvirus 1

Introduction

Feline Herpes virus (FHV-1) causes an upper respiratory tract infection: Feline Viral Rhinotracheitis.

Viruses and bacteria are involved in the complex, with the most frequent aetiologic agent being FHV-1, and less frequently feline calicivirus and/or Chlamydophila psittaci. All three agents infect URT respiratory epithelium, although FHV-1 has the highest affinity for this epithelium. Feline calicivirus more frequently infects the oral mucosa -> ulcerative stomatitis and C. felis more frequently infects the conjunctival epithelium -> chronic conjunctivitis. All three together will result in the disease complex 'cat flu'.

Infection of the respiratory epithelium by FHV-1 results in a typical neutrophilic rhinitis with intraepithelial intranuclear eosinophilic inclusion bodies, with expected clinical signs. Resolution of these clinical signs usually occurs by 7-14 days, however, FHV-1 remains latent in the trigeminal ganglion, and can reactivate at times of stress. It can infect the cornea - ulcerative keratitis. FHV- 1 is the most common cause of keratitis and corneal ulcers in cats and gummy eyes in kittens.

Occasional mortality can occur in the kitten or immunocompromised animals usually associated with secondary bacterial infections.

The virus is widespread and common. It can cause serious infections as well as latent infections which can be reactivated on boarding or at other periods of stress.

Clinical Signs

Upper respiratory tract signs such as rhinitis, tracheitis and sinusitis as well as keratitis and corneal ulcers. The corneal ulcers intially have a dendritic appearence, which is considered pathognomic. In combination with other agents, will cause 'cat flu' which will include sneezing, coughing, gummy eyes, nasal discharge, dyspnoea and conjunctivitis.

Diagnosis

Clinical signs and history are usually used as a presumptive diagnosis prior to definitive diagnosis via laboratory tests.

Nasal swabs on first week of infection can be cultured for virus isolation, plus a swab of the eye.

Treatment

For keratitis with corneal ulcers treat with subcutaneous omega interferon and give topical trifluorothymidine (thymidine analogue) on eyes.

Control

Killed and live vaccines are available. Live vaccines have provoked symptoms in immunosuppressed kittens and are no longer used in the UK.

References

Bridger, J and Ruseel, P, (2007) Virology Study Guide, Royal Veterinary College

Ettinger, S.J. and Feldman, E. C. (2000) Textbook of Veterinary Internal Medicine Diseases of the Dog and Cat Volume 2 (Fifth Edition), W.B. Saunders Company

Ettinger, S.J, Feldman, E.C. (2005) Textbook of Veterinary Internal Medicine (6th edition, volume 2), W.B. Saunders Company

Merck & Co (2008) The Merck Veterinary Manual (Eighth Edition), Merial

Feline Herpesvirus 1 Learning Resources
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