Unexpected isolation of virulent Newcastle disease virus from commercial embryonated fowls' eggs

The authors report a case of causal isolation of virulent Newcastle disease virus (NDV) from embryonated eggs. The virus was isolated from uninfected chicken embryo liver and fibroblast cultures prepared from commercial embryonated fowls' eggs. A serological and virological investigation carried out on the breeders which had laid those eggs showed high titres against NDV, and virus isolation from cloacal swabs. The virus was also isolated from the progeny of the same breeders which showed no clinical signs of ND, following episodes of mortality. Vertical transmission of the virus is discussed.