Feline Herpesvirus 1

VIRUSES HERPESVIRUSES

Pathogenesis

• Upper respiratory tract infection: Feline Viral Rhinotracheitis
  • Viruses and bacteria are involved in the complex
  • The most frequent aetiologic agent is 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
    • C.psittaci more frequently infects the conjunctival epithelium -> chronic conjunctivitis
  • Infection of the respiratory epithelium by FHV-1 results in a typical neutrophilic rhinitis with intraepitheial intranuclear eosinophilic inclusion bodies, with expected clinical signs
  • Resolution of clinical signs usually occurs by 7-14 days
  • FHV-1 remains latent in the trigeminal ganglion, and can reactivate at times of stress: Can infect the cornea -> ulcerative keratitis
  • Occasional mortality in kitten or immunocompromised animals usually associated with secondary bacterial infection
• Erosions can affect the bronchi, resulting in interstitial pneumonia
• Most common cause of keratitis and corneal ulcers in cat and gummy eyes in kittens
  • Rupture is a particular risk

Epidemiology

• Widespread
• Serious infection
• Latent infection can be reactivated on boarding

Diagnosis

• Nasal swabs on first week of infection can be cultured for virus isolation

Treatment

For keratitis with corneal ulcers:

• Subcut omega interferon
• 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