Pathogenicity On Ducks Of H9N2-AIV In The High Titer Of Antibody

Avian influenza, which was called avian flu (Avian Influenza, AI) for short, is the infectionand/or disease syndrome caused by Avian Influenza Virus A-type that was assigned toOrthomyxoviridae family. There have been a number of scholars have who had isolated thesame subtype of avian flu virus from sick chickens of different area since H9N2subtypeavian influenza was first reported epidemic in China in1994. H9N2subtype avian influenzavirus has become the main type in China nowadays analyzed by the existing report. It makesmore and more serious damages to the poultry industry and it aroused people widespreadinterest in it especially for the links with public health aspects.The study contains three parts:Part1: Isolation and identification of H9N2-AIVA strain virus isolated from broiler was identified as paramyxovirus by HA, HI. The resultsuggested that the virus can able to agglutinate chicken red blood cells, which can beinhibited by H9N2-AIV classic antiserum, but can’t be inhibited by Newcastle disease virus(NDV) and EDS-76classic antiserum. A specific strip was cloned by PCR and RT-PCR. Thevirus was identified as H9N2-AIV according to the above results and named SD01strain.EID50of chick embryos is10-7.50/0.1ml.Part2: Pathogenicity on ducks of H9N2-AIV in the high titer of antibodyThe60300d old Cherry Valley ducks were artificially infected through the eyedrops,dripping from nose and tracheal injection in the high titer antibody, the incidence, change ofautopsy clinical symptoms of ducks were observed. Their bloods were collected to be carriedout the detection of blood parameters after infection at the3,6,9day, observation ofdetoxification conditions of the experimental group and negative control group were doneusing the established RT-PCR detection methods. The fallopian tube, liver, lung trachea andso on were collected to be fixed and cut sheet by conventional H.E. staining. Then theHistopathological changes of these organs were observed. The distribution of the H9N2-AIVin ducks issue was studied with IFA (indirect fluorescent antibody test); The results suggest three experimental groups were caused lower ingestation, shedding tears, defecating whiteloose stools and other symptoms. The content of total protein (TP), glutamate pyruvatetransaminase (ALT), glutamic-oxal(o)acetic transaminase (AST) and alkaline phosphatase(AKP) significantly changed after infection. Histopathological changes were characterized bygranular degeneration and vacuolar degeneration in the liver, catholicity hemorrhage andinflammatory cell infiltration in the lungs, fiber protein exudate from the fallopian tube. IFApositive signals were mainly distributed in the trachea, fallopian tube, lungs, liver andpancreas. But the spirit of ducks was very fine, all physiological indexes were close to normal,positive signals were not detected by IFA in the control group.Part3: Pathogenicity on ducks of H9N2-AIV in the low titer of antibodyThe300d old Cherry Valley ducks were artificially infected through dripping from nose inthe low titer antibody, the incidence, change of autopsy clinical symptoms of ducks wereobserved. Observation of detoxification conditions of the experimental group and negativecontrol group were done using the established RT-PCR detection methods. The fallopian tube,liver, lung trachea and so on were collected to be fixed and cut sheet by conventional H.E.staining. Then the Histopathological changes of these organs were observed. The distributionof the H9N2-AIV in ducks issue was studied with IFA (indirect fluorescent antibody test);The results suggest experimental group was caused serious lower ingestation, shedding tears,defecating white loose stools and other symptoms. The content of total protein (TP),glutamate pyruvate transaminase (ALT), glutamic-oxal(o)acetic transaminase (AST) andalkaline phosphatase (AKP) significantly changed after infection. Histopathological changeswere characterized by granular degeneration and vacuolar degeneration in the liver,catholicity hemorrhage and inflammatory cell infiltration in the lungs, serious degenerationand thanatosis in the cardiac muscle fibre. IFA positive signals were mainly distributed in thelungs, liver, heart and pancreas. The degree of disease is more serious with the high titer ofantibody. But the spirit of ducks was very fine, all physiological indexes were close to normal,positive signals were not detected by IFA in the control group.