A/Turkey/Oregon/71, an Avirulent Influenza Isolate with the Hemagglutinin of Fowl Plague Virus

A/Turkey/Oregon/71 (A/Ty/Ore/71), a recent avirulent influenza isolate, had the hemagglutinin of fowl plague (Havl) and a neuraminidase similar to that of A/Tern/South Africa/61 (Nav2). Chickens inoculated with viable A/Ty/Ore/71 influenza virus developed hemagglutination-inhibition (HI) antibodies against that virus and also against fowl plague virus (A/FPV/Dutch/27). No disease signs resulted from the A/Ty/Ore/71 injections. Chickens immunized against A/Ty/Ore/71 virus survived intratracheal and contact-challenge exposures to high doses of virulent fowl plague virus (A/FPV/Dutch/27). Unimmunized hatchmate control chickens housed in the same room had classical signs of fowl plague and died, with typical lesions of fowl plague, after challenge exposure. Fowl plague virus was isolated from their lungs in large