[Isolation, identification and typing of Newcastle disease virus isolates in a chick embryo cell culture]

Routine methods of investigation were employed in parallel experiments for the isolation (in chick embryos), identification (serologically via HI), and typing (MDT, ICPI, IVPI, and via cloacal tests) of local isolates and standard strains of the Newcastle disease virus (NDV). The results were the same as those obtained by the single-phase complex investigation after the plaque technique method in a monolayer cell culture of chick embryo fibroblasts under agar cover. The cultures were inoculated with tissue suspension centrifugate in multiple dilutions of trachea and lung, spleen and liver, and brain of experimentally infected birds, using local isolates (13 in all) and standard strains of NDV (6 of the various types) as well as of birds that died of Newcastle disease (3 cases). The complex cell culture technique of investigation included plaque-forming under agar (and under agarose as well) following the direct inoculation with the infectious tissue suspensions in the presence of a normal (known negative), resp., specific hyperimmune serum against Newcastle disease. It also included a plaque-neutralization (plaque reduction) test and tests for hemadsorption and elution of erythrocytes--all made use of in a single planned programme of investigation. This technique, which is a modification of the one suggested by Beard et al. (1970) and known as single-phase complex plaque technique, provides the simultaneous isolation and identification of NDV isolates, which may well be coupled with some of the routinely practiced methods for definitive isolate typing (e. g., with the cloacal test for velogenic, and with MDT for lento- and mesogenic isolates). Thus, time can be saved, and labour and means are reduced, i. e., the laboratory diagnostics of ND may be perfected.