Development and application of an improved infectivity assay for the standardization of avian encephalomyelitis...

An improved infectivity assay for avian encephalomyelitis viruses (AEVs) is described in which susceptible 7-day-old chicken embryos were inoculated with dilutions of a particular AEV strain and, after incubation for 12 days, the presence of viral antigen in brains was detected by an enzyme-linked immunosorbent assay (ELISA). The assay (the brain antigen ELISA), which may be used for the titration of both egg-adapted and non-egg-adapted strains, can be completed within 12 days. For the conventional essays of non-egg-adapted vaccine strains, embryos are infected in ovo and hatched chickens examined for neurological signs after 3-4 weeks. No animal handling facilities are required with the brain antigen ELISA and results of comparable sensitivity to the hatch-out assay were obtained.