Avian Encephalomyelitis Virus. II. Pathogenesis in Chickens

Abstract

SUMMARY Chickens susceptible to AE (avian encephalomyelitis) were inoculated per os with a field strain of AE virus at one day and 6, 12, 18, and 24 weeks of age. Those exposed at one day old became fluorescent-antibody-positive in pancreas sections at 5 days postinoculation (PI). On subsequent days, reactions were positive in sections of brain, ventriculus, heart, lung, proventriculus, kidney, ileum, cecum, rectum, liver, esophagus, crop, skeletal muscle, spleen, and ovary, persisting for various periods. Reactions persisted over a longer period in sections of brain (cerebrum), being present through 30 days PI. Chickens exposed at 6, 12, 18, and 24 weeks of age failed to show positive fluorescent-antibody reactions in any of the 22 different tissues examined periodically throughout the testing period. Preexposure serum samples were all negative for AE antibodies by the virus-neutralization (VN) test. Samples collected from survivors at termination (50 days PI), however, had neutralizing indices ranging from 3.7 to 4.4. These results would indicate that all groups exposed at 6 to 24 weeks of age had undergone a response to the virus even though sites of virus localization could not be detected by the FA technique, as found in birds exposed at 1 day old.