Introduction
A herpesvirus (pathogenicity can vary) infection of chickens, pheasants, peafowl and turkeys with a morbidity of 50-100% and a mortality usually 10-20% but sometimes up to 70%. Recovered and vaccinated birds are long-term carriers. The route of infection is via upper respiratory tract and conjunctiva or possibly oral and the course of the disease is up to 6 weeks. Fairly slow lateral spread occurs in houses. Transmission between farms can occur by airborne particles or fomites.

The virus is highly resistant outside host but is susceptible to disinfectants. Movement and mixing of stock and reaching point of lay are predisposing factors.

Signs
Dyspnoea.
Gasping.
Coughing of mucus and blood.
Drop in egg production.
Ocular discharge.
Sinusitis.
Nasal discharge (low pathogenicity strains).

Post-mortem lesions
Severe laryngotracheitis, often with blood in lumen, caseous plugs may be present.
Microscopically - intranuclear inclusions in tracheal epithelium.

Diagnosis
Signs, lesions, in severe form may be enough. Isolation in CE CAMs, histology, IFA, PCR. Differentiate from Newcastle disease, severe bronchitis. Sera may be examined by VN or Elisa.

Treatment
None, antibiotics to control secondary bacterial infection if this is marked.

Prevention
Quarantine, vaccination, if enzootic or epizootic in an area, after 4 weeks of age. All-in/all-out operation. Keep susceptible stock separate from vaccinated or recovered birds. Apply strict biosecurity in moving equipment or materials between these these categories of stock.