Improved potency test for live avian encephalomyelitis vaccines

Potency tests were carried out on live avian encephalomyelitis virus (AEV) vaccines. Vaccines were titrated in chick embryo brain cell cultures using an indirect fluorescent antibody test just before vaccination. Groups of chickens were inoculated orally with graded doses of each vaccine. After three weeks serum was taken from the chickens and examined for antibodies to AEV by indirect enzyme-linked immunoassay (ELISA). The chickens were then challenged by intracerebral inoculation of virulent AEV and monitored for signs attributable to clinical AE. The results showed a relationship between virus content, protection and antibody development. It is recommended that serological evaluation using ELISA replace the challenge step in potency tests for live AEV vaccines.