Infectious laryngotracheitis causes respiratory disease, particularly of the upper respiratory tract.

The clinical signs vary from mild to severe respiratory disease associated with coughing of mucous and blood, gasping, runny eyes, nasal discharge, swollen head and decreased production because chickens cannot eat or drink properly.

The virus spreads slowly within houses but can spread more quickly in free-range chickens.  Should an outbreak of laryngotracheitis occur on the farm, immediately begin a programme of vaccination starting with the chickens furthest from the infected area and work towards the diseased chickens.  After recovery from infection some birds remain carriers.