[Diagnostic value of the hemagglutination inhibition reaction in Newcastle disease of hens].

Investigations were carried out using RPHA on 5299 blood serums, originating from 235 hen flocks vaccinated in four ways: Flox and orally with the vaccine strain La Sotta, intramusculary with Komarov's vaccine strain and by aerosol using the strains La Sotta and Komarov. Two hundred and eleven blood serums originating from 12 flocks, in which fowl pest was detected, were also investigated. Postinfection titer dynamics was followed in three flocks containing 20000 birds. It was established that aerosol vaccination results in highest mean geometrical titers--log2 6.3 on the average; intramuscular vaccination--in log2 5.9, oral vaccination--in log2 5.3, and Flox vaccination--in log2 4.7 on the average. The maximal value of the vaccine titers did not surpass log210, while post infection titers were of higher order and reached up to log214, which is of diagnostic value. Postinfection titers of higher than log210 value were preserved up to 5 months from the beginning of the disease, a fact of retrospective diagnostic value.