[Comparative studies of methods for the detection of immune carriers of the Newcastle disease virus in poultry].

Mass prophylactic vaccinations have radically chaugned the clinical syndrome, pathogenesis, and morphological picture of the Newcastle disease: clinically it is manifested with respiratory troubles, and morphologically--with tracheitis. The method for isolating the virus on chick embryos from immune birds have proved undependable: the higher the immunity of birds, the lower the probability of virus isolation. Following the vaccination of birds after the adopted prophylactic programme and at the three-fold vaccination with a lentogenic La Sota strain and four-fold vaccination with a mesogenic Komarov strain precipitating antibodies have been detected in single serum samples only. In the presence of respiratory troubles in immune birds the rise of antiheamagglutination titers and the mass manifestation of precipitating antibodies in the blood serum is said to be an indication of the presence of a field of velogenic virus, while HI and AGPT are suitable methods for the detection of immune carriers of Newcastle disease. These can be used also for the differential diagnosis of the latent forms of infectious bronchitis, infectious laryngotracheitis, the diphtheroid form of pox, and CRD. In order to restrict and do away with the velogenic field strains of the Newcastle disease virus a suggestion is made to kill all birds that have shown respiratory troubles and positive results in virologic and serologic examinations through HI and AGPT.