| Highly pathogenic avian influenza (HPAI) is a serious and often fatal infection in domestic poultry. An epidemic can cause significant economic damage. The avian influenza H5N1 virus (AIV-H5N1) subtype has boon associated with HPAI phenotype. In China, the eradication of HPAI is that all of the infected poultry are slaughtered and the poultry around are instantly vaccinated. But the antibody against AIV-H5N1 ascends to the effective titer only at postinoculation 14 days. This paper reports the preparation of egg yolk immunoglobulins against AIV-H5N1 (AIV-H5 IgY) and the effectiveness of AIV-H5 IgY in blocking chicken infection with AIV-H5N1.The laying hens were highly immunised by inoculating 5 times with the killed AIV-H5N1 (A/chicken/ Hebei.China/2001) vaccine. AIV-H5 IgY HI titres reach to 210~28 and last more 5 months.The AIV-H5 IgY was purificated by degreasing with acetic acid-sodium acetate buffer and salting out with solid ammonium sulfate. The inactivation with 0.05% of formalin under 4# for 24 hours did not effect the protective efficiency of AIV-H5 IgY against AIV-H5N1. The protective rate could be 100% by injecting AIV-H5 IgY (HI titre 210, with 1.5ml firstday, 1ml /day for 2days ) 0, 24 hours before H5N1 virus challenge, but the challenged chickens without AIV-H5 IgY injection were wholly dead.The protective efficiency of AIV-H5 IgY is not obviously improved by combination with the killed vaccine, but enhanced in some extent with amantadine.
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