Reed Neurological Research Center, UCLA School of Medicine, Los Angeles, California.

Various clinical, virological, immunological, and morphological aspects of velogenic Newcastle disease were defined in chickens inoculated by natural routes with the Missouri-(H) Len 1950 strain. The disease initially appeared as a severe pneumonitis from which most birds recovered. Several days later, many of these birds developed severe encephalitic signs, largely referable to inflammatory changes in the cerebellum. During the pneumonic stage, virus was easily isolated in relatively high titers from the brains of all chickens, and viral products were easily detected in Purkinje neurons. However, when the encephalitis developed, virus was isolated irregularly and in low titers from brains, and morphological evidence for the presence of viral products could not longer be obtained. The encephalitic disease is discussed in relation to encephalitic syndromes induced by other neurotrophic viruses.