Isolation, Identification And Some Biological Characterization Of Proventriculus Type Infectious Bronchitis

First of all, 5 virus isolates were isolated from chicken flocks suspected infectious proventriculitis (IP) in Hebei in the present study. Through serological identification, infectious bronchitis virus (IBV) - Newcastle disease virus (NDV) interference test and animal test as well as other methods, the viruses were identified as IBV. The viruses have no direct hemagglutination activity to chicken red blood cells. Hemagglutination activity of allantoic fluids after treated by 1% trypsin could be inhibited by IBV serum. The viruses could interfere with the proliferation of LaSota strain of NDV in SPF embryo.The full-length of membrane protein gene (M gene) of two virus isoltes were successfully amplificated by RT-PCR method. The M gene each composed of 681 nucleotides, and encoded 226 amino acids. After comparison with the M gene nucleotide sequence and deduced amino acid sequence and analysis of phylogenetic relationship of 19 strains or isolates of IBV from GenBank, found that 2 isolates of proventriculus type IBV had 100% homology in nucleotide sequence and amino acid sequence. There had 86.8% ~ 93.0% homology in nucleotide sequence, had 87.5%~96.1% homology in amino acid sequence between 2 proventriculus type IBV isolates and 19 reference strains. The genetic relationship of 2 proventriculus type isolates were more near from the BJ strain, QX strain and CK/CH/LSHHI/03 strain, but more far from CU-T2 strain.Viral proventriculitis were not easy to successfully reproduce in the laboratory, so synergistic pathogenesis between proventriculus type IBV and NDV in chickens were performed, to reveal the cause and pathogenic mechanism of viral proventriculitis through observation of clinical symptoms and pathological examination and viral antigen detection. Viral proventriculitis cases were successfully replicated. Illness and death were found in each infected group. The mortality in group a, group c and group d each was more than that in group A, which infected with tissues from natural diseased chickens. The highest fatality rate was in group c,while the lowest fatality rate in group b. The results showed that NDV significantly could enhanc fatality rate of viral proventriculitis cases.Pathologic examination showed pathologic changes were similar in each infected group, lesions of proventriculus were slight in early infection, but to the late, lesions gradually significant. Swelling proventriculus, thickened wall, proliferated lymphocytes in lamina propria and (or) gland were observed, while the control group had no pathological changes. The results showed that the proventriculus was an important target organ for IP. But gross and microscopic lesions of proventriculus induced by 4 kinds of infection methods were not significant than that in group A. So that other factors may be involved in swelling proventriculus of IP cases.The viral antigen could be detected in mucosa and compound tubular gland endepidermis of proventriculus as early as at 1d post inoculation(PI), and also be detected until 35dPI. It indicated that proventriculus type IBV and NDV could replicate in early time of infection, and continual replicate in long time.