Spray vaccination of chickens using infectious laryngotracheitis virus

Day-old chickens were vaccinated with the SA2 strain of infectious laryngotracheitis vaccine using a coarse spray and 14-day-old chickens were vaccinated using a coarse or a fine (Turbair Vaccinair 240) spray. The Conjunctiva was the most common site of infection in all cases but this almost invariably led to involvement of the nasolacrimal ducts. Other sites in the nasal cavity were affected less frequently. The clinical consequences of infection in day-old chickens were too severe for field use but the mortality (0 to 1.4% in different experiments) in 14-day-old chickens may be acceptable in some circumstances although about 9% developed infection of the trachea. It is concluded that a less pathogenic vaccine is needed if spray vaccination with ILT is to be recommended as a routine procedure particularly for day-old chickens.