Felis ISSN 2398-2950

Feline herpes virus: feline rhinotracheitis virus

Introduction

Classification

Taxonomy

• Family: Herpesviridae.
• Subfamily: Alphaherpesvirinae.

Active Forms

Clinical Effects

Epidemiology

Transmission

• Route of infection: intranasal, oral or conjunctival.
• Virus is shed in oronasal secretions from 24 hours post-infection and persists 1-3 weeks.
• Transmitted by direct contact and by short-distance aerosolization through sneezing.
• Indirect via contaminated food bowls, hands, etc (less important than direct transmission due to virus susceptibility to dessication, disinfectants, etc).
• Fomite transmission is more important than aerosol in cats due to small lung tidal volume.

Pathological effects

• Neutralizing antibody recognizes gp60, the viral hemagglutinin, which is essential for attachment to cells.
• Neutralizing titers are low: 1:16-1:64.
• Neutralizing antibodies appear 20-30 days post-infection.
• Infection is lifelong and latently infected cats may still have neutralizing antibodies.
• Maternally derived antibody may last until 6-10 weeks of age.
• FHV-2 serologically distinct from FHV-1.
• Antibodies detected by immunofluorescence may decrease to low or undetectable levels within several months.

• Virus growth occurs in the epithelium of the nasal mucosa, conjunctiva, tonsil and nasal turbinates: tissue damage is due to viral cytolysis. Clinical signs of upper respiratory tract disease due to this damage. May see severe nasal and/or ocular discharge, sneezing, anorexia, depression.
• Corneal lesions seen on days 3 and 12 of primary infection, in kittens: corneal edema Eye: corneal opacity, ulceration Ulcerative keratitis and rupture of eyeball often around 2-4 weeks of age. In older kittens and cats: dendritic keratitis, adhesions to conjunctivae or to iris.
• May leave surviving cats with chronic ocular discharge , chronic sinusitis Sinusitis or rhinitis Rhinitis.

Other Host Effects

• All infected cats become latently infected as carriers.
  Kittens may become latent carriers without ever showing signs.

Control

Control via chemotherapies

• For ulcerative keratitis: 0.1% ophthalmic solution of 5-iododeoxyuridine 4-6 times daily for 3-5 days (Acyclovir Acyclovir, used for herpes simplex in man, less active against FHV).
• Interferon useful for ocular disease - L-lysine tablets twice daily (endogenous interferon inducer).
• Broad spectrum antibiotic cover useful against secondary bacterial infection.
• Good nursing, especially to encourage feeding, as cats will not eat what they cannot smell (use strong-smelling foods like sardines).
• Eucalyptus oil on bedding or bandanna, or steam inhalation, to aid clearing of nasal passages.

Control via environment

• Disinfectant: Most detergents or bleach diluted 1:32 in water with washing-up liquid.

Vaccination

• Attenuated living and inactivated systemic vaccines available.
• Inactivated vaccine

Other countermeasures

• FHV prevention in kittens:
  • Boost queen's immunity before conception.
  • Isolate queen from other cats before birth of kittens.
  • Ensure good intake of colostrum to supply maternally derived immunity.
  • Wean kittens early, at 2-3 weeks of age, and keep isolated from all other cats.
  • Vaccinate at 8 and 12 weeks of age.
  • In some kittens early vaccination is used, but is not licensed in UK.

Diagnosis