ABSTRACT
Infectious laryngotracheitis (ILT), caused by infectious laryngotracheitis virus (ILTV) or gallid herpesvirus 1, is an economically important respiratory disease of chickens worldwide. The natural hosts include chickens, turkeys, and pheasants. Although all ages of chickens are vulnerable to ILTV, the most sensitive age is above 3 weeks [1,46]. In the virulent form of ILT, the clinical signs include gasping, coughing, bloody mucus in trachea, and dyspnea, which lead to suffocation. This form can result in 90%–100% morbidity and 5%–70% mortality. The signs of the mild form include nasal discharge, conjunctivitis, reduced egg production and shell quality, decreased weight gain, and increased condemnation rate. The mortality and morbidity of the mild form is about 5% [2]. Despite the availability of various vaccines (attenuated live, inactivated, recombinant), ILTV still causes signicant economic losses.
