In the January of 2008,respiratory signs were observed in the chicks of a layer farm in Cangzhou,Hebei province.Necropsy of the dead chicks revealed that the kindey was swollen and distended with uric acid crystals.Kidneys and tracheas were collected for virus isolation.An IBV virus was identified by viral interference test,HA test,animal regressive research,cross-neutralization and RT-PCR.The virus was designated 0801 strain.The date of cross-neutralization indicated that the 0801 strain and Ma5 vaccine strain belong to the same serotype.The S1 gene of 0801 strain was amplified,cloned,sequenced and analyzed.The results showed that S1 gene was composed of 1620 nucleotides,homologies of nucleotide and amino acid sequences of S1 gene between 0801 strain and Massachusetts-type vaccine strains was both about 75%.

To get in-depth understanding of microbial aerosol development and transmission from chicken house to the surroundings,and to make comparisons between two methods,ERIC-PCR and PFGE were used to genotype bacteria.Escherichia coli was used as indicator bacterium in this study,air samples were collected by the Andersen-6 sampler from air of the 2 chicken houses,at 10-and 50-m upwind sites and 10-,50-,100-,200-,and 400-m downwind sites outside of the chicken houses;meanwhile,chicken manure samples were collected to isolate and identify E.coli.Then,for each chicken house,genotyping of E.coli isolates of different origins were carried out by ERIC-PCR and pulsed-field gel electrophoresis(PFGE).The mode of microbial aerosols in a chicken house to transmit to its surroundings was determined,according to genetic distances of E.coli strains isolated at different samplings.And then,the results were compared to analyze the characteristic and applicability of the two methods.28 strains were collected and the homology identification was carried out by the combination of ERIC-PCR and PFGE.The results showed that,bacteria in chicken manure were able to form into aerosols,and transmit to the surroundings of the chicken houses through air exchange to a different distance based on different meteorological conditions,leading to biological contaminations of surroundings,and transmission of microbial pathogens.The comparison of the two methods suggested that the discriminability of PFGE is higher than taat of ERIC-PCR.The two methods are both based on the different genetic characteristics of DNA to classify strains,hence combining the two methods to analysis the genetic relationship of strains.