Isolation and distribution of West Nile virus in embryonated chicken eggs

West Nile virus (WNV) was identified from domestic psittacine birds by inoculating embryonated chicken eggs. Most of the embryos died 5 days postinoculation; flavivirus was detected in some by negative-staining electron microscopy. Immunohistochemistry performed on the embryos and their supporting structures detected the WNV antigen mainly in the chorioallantoic membrane, regardless of the inoculation route or passage number. WNV antigen was also found in the embryonic muscle (both skeletal and smooth muscles) and in multifocal areas of the skin. WNV was not detected in the viscera of the embryo or yolk sac. This study provides evidence of isolation and identification of WNV via embryonated chicken eggs.