Drinking water vaccination against infectious laryngotracheitis.

Chickens varying in age from ten days to five years were vaccinated with 10(1.3), 10(2.3) and 10(3.3) EID50 per bird of a commercial infectious laryngotracheitis drinking water vaccine. The vaccine gave no adverse reaction in the dose range tested. Five weeks after administration of 10(3.3) EID50 per bird 70% were protected against the intratracheal challenge with virulent infectious laryngotracheitis virus. Doses of 10(1.3) and 10(2.3) EID50 per bird did not give protection. No serological response could be detected by the neutralization test even in the group that had received 10(3.3) EID50 per bird. No contact spread of virus was detected from 14 days post-vaccination. Carriers of vaccine virus could not be demonstrated.