Isolation And Identification Of Infectious Bronchitis Virus (Chongqing Strain) And It's Biological Characteristics

Infectious Bronchitis (IB) is caused by the avian infectious bronchitis virus (IBV), an acute and highly infectious respiratory disease. Since break out in USA in the 1930s, IB have become a major epidemic of infectious disease around the world. Currently, IB has been found in China north, northwest, southwest and northeast provinces, municipalities and autonomous regions. While IB has been widely used vaccines, but the incidence is still widely. Especially in the immunized chickens often broke out, resulting in serious economic losses to the farming industry.IBV is a single-stranded RNA virus, the gene of the virus always mutated owing to the it's point-mutation and gene recombination, So more infectious bronchitis virus serotype, has more than 30 titles . The known serotype can be classified into respiratory symptomatic serotypes such as Conn,Iowa97,JMK,Florida,Arkansas99 and nephritic symptomatic serotypes such as M₄₁, Holte, Gray, Australia and other serotypes .April of 2006, there is a serious outbreak of avian infectious bronchitis disease in a farm which is in chongqing. In order to identify the exact causes , we isolated and identificated the pathogenic virus and researched its biological characteristics.Isolation and identification: Trachea, kidney and caecal tonsils samples collected from suspect IB outbresks were submitted for virological investigation. Clarified suspensions(10%w/v) of tissue homogenates were inochlated into the allantoic cavity of eggs of 9- to 11-day-old embryonated specific pathogen free chicken eggs, the virus was passaged three times with this method for the study.To known whether the allantoic fluid have NDV or AIV,HA test was deteced and the result showed that the allanotoic fluid have not hemagglutination to chiken's 1% red blood cells.The allantoic fluid was centrifuged by hypervelocity centrifuge, Sediment was collected and examined by negative contrast electron microscopy four thr presence of coronavirus particles. the sediment can be observed typical coronabirus partickes which viral spikes surround. Then,we had dealed the allantoic fluid by I type of phosphoesterase C for HA test,the result showed that theallantoic fluid have hemagglutination. So we can drew a primary conclusion that the virus weisolated is a strain of IBV.The following reseach including chiken embryo dwarfed test, NDV-B1 interference test and animal regressive reseach confirmed the presence of IBV in the allantoic flued. The biologically character was determined in after research.Serum VN test shoued that isolated strain is a mutation strain of IBV gived fewer or no cross-reaction to the familiar serotype of IBV.For further research, the whole sequence of S1 gene was cloned and analyzed by RT-PCR using specific primer . Identity of the S1 gene sequence between the isolated strain and other serotypes of published IBV sequence is < 83%. Our analysis has shown that B1648 Belgium.strain has highest homology with chongqing strain.