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Abstract
VII.Immunological Studies on Highly Virulent Avian Influenza (H5) in Some Avian Species:
Studies were carried out to detect the level and waning of maternal antibodies in chickens, detect antibodies in serum of progeny in relation to yolk and serum of vaccinated chicken and turkey breeders and to evaluate the developed immune response by haemagglutination inhibition (HI) and AGP tests in chickens, turkeys and ducks following s/c vaccination with inactivated oil-emulsion H5N2 avian influenza vaccine.
These studies revealed the following results:
1- Newly hatched chicks posses high level of maternally derived antibodies which remain above the protective titer during at least first 2 weeks of age. The waning of maternally derived antibodies is approximately linear and disappeared at 6 weeks of age.
2- The level of AI antibodies in serum of progeny was related to level of antibodies in yolk and serum of vaccinated dams. The amount of antibodies in extracted egg yolk was 48% from breeders and the level of antibodies in serum of progeny reached 91% from breeders for chickens, while the amount of antibodies in extracted egg yolk was 47% from breeders and the level of antibodies in serum of progeny reached 86% from breeders for turkeys.
3- When chicks were vaccinated s/c with 0.2ml of H5N2 vaccine, relatively late and low immune response where HI titers were evident 3-5 weeks p.v.
4- When chicks were vaccinated s/c with 0.5ml of H5N2 vaccine, satisfactory immune responses as well as adequate protective HI titers were evident 2-6 weeks p.v.
5- When chicks were revaccination (booster dose) at 6 weeks apart from priming, immune response showed rapid and high increase where HI titers reached 9.8 log2 within 3 weeks p.v.
6- Vaccination of turkeys with 1ml of H5N2 vaccine resulted in satisfactory immune responses as well as adequate protective HI titers which persist for 7 weeks p.v.
7- Ducks were vaccinated s/c with either 0.5ml or 1ml of H5N2 vaccine. Immune responses were high and persisted for 6 and 7 weeks p.v. respectively.