Comparative pathogenicity of avian encephalomyelitis viruses in chicken embryos.

Multiplications of wild, various embryo-adapting and completely embryo-adapted avian encephalomyelitis (AE) viruses in chicken embryos were compared by the fluorescent-antibody technique (FAT). With a wild AE virus, viral antigens were randomly seen in the central nervous system (CNS), appearing least often in the cerebellum. Other organs seldom became test positive, except for heart and kidney. Even with 4 chicken brain-passaged viruses in the process of embryo adaptation, there was little augmentation of antigens except in the alimentary tract. However, the 2 midpassage viruses showed a peculiar localization of antigens in the white matter of the lumbosacral cord, together with the appearance of test-positive spinal ganglion cells. With 2 strains of embryo-adapted AE virus, the antigens appeared first in the spinal ganglion cells and secondly in the lumbosacral cord and then spread to the cerebrum. Subsequently, clinical signs of AE were evident. This peculiar invasion order was a prominent feature.