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Abstract
- Studies on evaluation of avian influenza vaccines in field :
Studies were carried out to evaluate the developed of humoral immune response and build up of protective hemagglutinin inhibition (HI) titers in chicks Saso crossed with local chickens type, following subcutaneous (S/C) vaccination with two types of inactivated oil-emulsion avian influenza virus (AIV) vaccines, reassortant H5N1 or H5N2 vaccines from different company origin .
- These studies revealed the following results :
1. When seven-day old, experimental chicks having low maternal antibody level were vaccinated subcutaneously with 0.5 ml / bird of H5N1 vaccine, satisfactory humoral immune response as well as some early protective HI titers were evident 2-8 weeks post vaccination . However, H5N2 AIV vaccine give relatively low and variable humoral immune response and inadequate protective HI titers were evident 2-8 weeks PV .
2. When 14 or 21 days old experimental chicks, having low maternal antibody levels were vaccinated S/C with 0.5 ml / bird of H5N1 AIV vaccine, the humoral immune response and the protective HI titer values were excellent and satisfactory 2-8 weeks PV .
3. When 14 or 21 days- old experimental chicks, having low maternal antibody level were vaccinated S/C with 0.5 ml / bird of H5N2 AIV vaccine, satisfactory humoral immune response were evident 2-8 weeks PV, and protective HI titer values were low.
The humoral immune response and the protective HI titers values which obtained by H5N1 AIV vaccine were more good and satisfied than that obtained by H5N2 AIV vaccine and also humoral immune response and protective HI titers were more good and satisfied in experimental chicks vaccinated S/C with 0.5 ml / bird of H5N1 or H5N2 AIV vaccines at 14 or 21 days of age, but chicks vaccinated at 14 days of age give more good immune response and protective HI titers than those vaccinated at 21 days .
However, relatively low and variable immune response and inadequate protective HI titers were obtained in chicks vaccinated at 7 days of age .
These results suggest the need for revising the vaccination schedule for chickens due to in correct vaccination age .
sera collected from experimental chicks which vaccinated subcutaneously with H5N1 and H5N2 AIV vaccines, when examined against heterologous antigens give antibody response lower than that obtained when sera examined against homologous antigens by about ( 1-2 log ) as judged by means of HI titers .