Experiences under Experimental Conditions on the Practical Value of Various Immunization Methods against Newcastle Disease

摘要

During 1970-1973 foreign publications have repeatedly drawn our attention to the latest large-scale spreading of the Newcastle disease (1,2,6,7,9,10,12,16,19). In places, the extremely virulent virus caused severe damages and economic losses even in vaccinated stocks resulting--often without visible symptoms of the disease--in decreasing egg yield (2,13a,13b,15). On the basis of experiences gathered in the course of epizootics certain countries have revised the practice of earlier vaccinations. In the laboratory, semi-field and field experiments the immune state of 146 chicks and 4023 older birds were investigated by the parallel application of the HI test and the challenge experiment.