Investigation Of H9N2 Avian Influenza Epidemiology In Shandong Area And Molecular Biological Detection Of Epidemic Strain

With the purpose of understanding the recent epidemic situation of H9N2 subtype avian influenza and the molecular and genetic evolution characteristics of epidemic strains from 2012 to 2013, 6385 serum samples were detected and 35 suspected cases were analyzed comprehensively which came from all of the Shandong include breeders, commercial layers and broilers chicken. A part of H9N2 subtype AIV were isolated by RT-PCR amplification of the HA gene fragment, were analyzed by sequencing and genetic evolution, and these virus receptors binding were detected. The results showed that in Shandong region HI antibody level of the immunized chicken groups were very high, especially in commercial laying hens that were almost more than 8 liters. The immunity passing rates of commercial broilers and commercial layer chickens were relatively low, while the suspected infection chickens were in higher proportion so the immune status of chickens was not optimistic existing a big risk of infection. By contrast, the eligible rates of breeder flocks were higher and the chickens suspected infections were relatively low so the risk of infection was lower. During the two years all the antibody level of group had some differences, but the immune status of all kinds of chickens in 2013 were better than 2012. With inspection of the 35 suspected cases after a comprehensive diagnosis, 19 cases were diagnosed as H9N2 subtype avian influenza with the characteristics of clinical symptoms, pathologic examination, then isolation and identification of 17 strains, including 6 strains of virus on the molecular biological characteristics were detected. The deduced amino acid sequences of cleavage sites in the six H9N2 isolates were typical low pathogenic motif(PSRSSR). Most of the isolates had eight potential glycosylation sites and all the isolates had an amino acid residue of leucine(L) at position 226(H3 numbering). In addition, these isolates were able to binding with both the SA 2, 3Gal and SA 2, 6Gal, which suggested that these viruses posed a threat to public and veterinary health. The continuing evolution of H9N2 influenza viruses in China emphasizes the importance of H9N2 influenza virus surveillance throughout this region.