Effects of three avian respiratory viruses on pathogenicity in tracheal organ cultures [chicks]

Comparison was made on effects among three avian respiratory viruses of known virulence in vivo, infectious bronchitis virus (IBV), Newcastle disease virus (NDV) and infectious laryngotracheitis virus (ILTV), on the ciliostasis patterns of tracheal organ cultures (OC) and the lethality patterns of chick embryos. A field isolate and a vaccine IBV which had caused rare and irregular lethality in chick embryos produced regularly ciliostasis in OC, but avirulent IBV with high pathogenicity for the embryos did not. The vaccine and virulent strains of NDV exhibited essentially the same pattern of ciliostasis with different patterns of lethality in the embryos. A low level of ciliostasis was presented by a vaccine ILTV, but not by a virulent ILTV. The results of comparative titration of the three respiratory viruses performed in OC, chick embryos and cell cultures showed that 0C were advantageous especially for the assay of IBV not adapted to chick embryos.