ABSTRACT
The distribution and prevalence of low pathogenic avian influenza virus in major live poultry wholesale markets around the Dongting Lake region ,China were investigated in our study to propose prevention and control measures on low pathogenic avian flu in the area of live poultry wholesale market .The samples were injected to SPF chicken embryos by allanto-ic cavity ,and then the allantoic fluid were harvested and used for hemagglutination (HA) .If it was positive by HA ,subtypes of the virus would be determined by hemagglutination inhibition (HI) and RT-PCT .We isolated 627 low pathogenic avian in-fluenza viruses in major live poultry wholesale market around Dongting Lake region systematically in winter and spring during 2009-2011 ,and the total separation rate was 22 .2% .The duck swab separation rate of low pathogenic avian influenza was the highest ,which was 24 .6% ,and the following was chicken swab that reached 21 .5% ,and the goose swab separation rate was 11% .We isolated 6 HA subtypes including H3 ,H4 ,H6 ,H9 ,H10 ,and H11 in every live poultry wholesale market ,and the separation rate of H9 ,H6 and H4 subtypes was relatively high ,which could reach 11% ,6 .3% and 3 .4% ,respectively . Those results indicated that recessive infection of low pathogenic avian influenza virus was serious in live poultry wholesale mar-ket around the Dongting Lake area ,and it was a great threat to the occurrence of avian flu .
ABSTRACT
The worldwide distribution and continuing genetic mutation of avian influenza virus (AIV) has been posed a great threat to human and animal health. A comparison of 3 isolates of AIV H9N2, A/chicken/Korea/KBNP-0028/00 (H9N2) (KBNP-0028), A/chicken/Korea/SNU8011/08 (H9N2) (SNU 8011) and an inactivated oil vaccine strain A/chicken/Korea/01310/01 (H9N2) (01310), was performed. The former 2 AIVs were isolated from field cases before and after the application of an inactivated H9N2 vaccine in 2007, respectively. The antigenic relationship, viral shedding, tissue tropism and genetic analysis were examined. The comparison of virus shedding from the cloaca and the oropharynx revealed that both isolates were more frequently isolated from the upper respiratory tract (90~100%) 1 day post inoculation (DPI) compared with isolation 5 DPI from gastrointestinal tracts (10~60%). Moreover, the isolate KBNP-0028 were recovered from all organs including bone marrow, brain and kidneys, indicating higher ability for broad tissue dissemination than that of SNU 8011. KBNP-0028 replicated earlier than other strains and with a higher titer than SNU 8011. In full-length nucleotide sequences of the NA gene and a partial sequence of the HA gene of SNU 8011, we found that there might be significant changes in tissue tropism, virus replication and genetic mutation in AIV H9N2 isolates.