Investigation Of Antibodies Against Newcastle Diseases Using HI Assay And The Harboring Of ND Virus In Chickens

The investigation for ND antibody during March 2008 to May 2009 in the center of Shangdong province showed that the antibody levels exceeded the normal immune levels and had a big discrete degree in many flocks, which were suspected of being infected by NDV. The proportions of infected flocks were 12% in AA broilers or spotted chickens , 20% in breeding hens, respectively. While it was as high as 51% in layers. The result s of HI test were verified by virus isolation, Quantitative Fluorescent RT-PCR and indirect fluorescent antibody (IFA) test .The result showed that the virus was isolated from 3 of the 4 groups (sample 1,2,3), and sample 4 was also detected as NDV positive by RT-PCR. The investigation showed that many poultry were infected by NDV though they did not show identical ND symptom. The biggest problem of controlling ND in China was poultry carrying NDV in high proportion.