The Molecular Epidemiological Studies Of Chicken Anemia Virus Infection In Wild Birds In Northeast China

CAV is the pathogen of chicken infectious anemia. It infects the chicks, causing immune suppression infectious diseases such as the increased mortality of chicks, aplastic anemia, bone marrow, lymphoid organs atrophy, like thymus. Epidemiological reports about CAV are mostly concentrated in poultry but wild birds are less. In1998, Japanese researchers found that the CAV can infect quail, dove and crow, attested that CAV can infect not only chicken but also others. The environment range for the survival of the wild birds are relatively large, and the migrations happen every year,If the wild birds can also be infected and carried the CAV,it will provide potential conditions that it is more rapid and wider range of spread,resulting in the difficult of prevention and control for CAV.The aim of this study was to investigate the epidemiology of CAV in wild birds in northeast of China. All1199samples were isolated from wild birds during2011to2012year.604samples were from wild waterfowl and most of them were wild duck samples;595samples were from land bird and most of them were small passerine bird samples. These samples were tested for the presence of CAV by polymerase chain reaction (PCR) and then the positive samples were inoculated in MDCC-MSB1cells for virus isolation. At last the presence of CAV antigen was examined by an indirect immunofluorescence assay (IFA). The CAV coding region was cloned and sequenced. We used all CAV isolates whose coding region gene was available in the GenBank database to investigate the evolutionary process of CAV in wild birds in China.The results show that the positive rate was5.34%of all wild bird samples, wild duck and small passerine bird detected positive (the positive rate was9.27and1.34percent). Wild birds infected with CAV have no apparent seasonal. Different kinds of wild birds with different PCR positive rate; blue head duck and pochard duck had the highest detection rate in wild duck; Short foot warbler had the highest detection rate in small passerine bird.7CAV were isolated from wild duck and another7CAV were isolated from small passerine bird by MDCC-MSB1cell culture and IFA. Sequence analysis showed that the coding regions of the14isolates were all1823bp and there were no insertion or deletion. VP1gene (1350bp) encode449amino acids, acidsVP2(651bp) encode216amino acids and VP3gene (366bp) encode121amino acids. Sequence analysis and phylogenetic study of the14isolates virus of the coding region gene has shown that there high degree of identity among the14isolates virus (98.2%-100%, respectively).3isolates virus of wild duck had the same sequence;7isolates virus of mall passerine bird had the same sequence too, but sequence similarities in the coding region gene between WDNE110502strain and other isolates were substantially lower. The nucleic acid homology of the field isolate was95.2%-99.9%and amino acid homology was88.1%-99.8%compared with Cux-1strain and other domestic and international reference strains. The highest homology between isolates virus and harbin strain were observed. Phylogenetic analysis based on the coding gene sequences of the14Chinese isolates and30strains from Genbank showed that all of the Chinese isolates with harbin strain and C14strain were from a genetic groups and CAU269-7strain,3177strain and other stains were from another groups. This is the first time that isolated CAV from wild birds and demonstrates wild birds could be infected with CAV. This result indicated that wild birds may play an important role in the transmission of CAV.