A new influenza A virus infection in turkeys. VI. Artificial immunization against the malignant virus strain turkey-Ontario 7732-66.

The immune reaction of turkeys and chickens to inactivated preparations of a virulent strain of avian influenza A virus has been examined. In both species any level of antibody detectable by the hemagglutination inhibition or serum neutralization tests was protective against the challenge exposure. However, some vaccinated birds were protected in the absence of detectable antibody. Chickens responded with higher and longer lasting antibody titers than turkeys to identical antigen preparations. Whereas the vaccine induced protection in chickens for at least 84 days, the immune protection in turkeys barely lasted 42 days. Immune birds responded to the live virus challenge with a marked rise in serologic titers which suggest that they were still susceptible to subclinical infection. These findings are discussed in their relationship to available data on classical fowl plague and influenza in mammals.