Studies on Avian Encephalomyelitis. V. Development and Application of an Oral Vaccine

Abstract

AVIAN encephalomyelitis (AE) of chickens has been plagu211 ing hatcherymen for a number of years. Two approaches toward reduction or elimination of losses from the disease have been reported. Schaaf and Lamoreaux6 were able to demonstrate that AE could be controlled by vaccination, producing a lasting immunity similar to that following natural outbreaks. A second approach, suggested by Taylor and Schelling,8 involved hatching only from flocks shown to have had the disease. The observation that many flocks become naturally infected with the virus during their lifetime makes such an approach feasible for hatcheries if they can afford to eliminate susceptible flocks as sources of hatching eggs. Schaaf's work stimulated much activity toward the development of better and safer vaccines. Also of primary significance was the finding by Jungherr et al.4 that AE virus could be adapted to produce lesions in chicken embryos. Those workers later reported7 that only eggs from susceptible flocks could be used to demonstrate the presence of the virus. Thus, this research provided much of the knowledge and technique necessary for testing immunity to AE. The development and use of embryo-susceptibility7 and