Studies with inactivated duck virus hepatitis vaccines in breeder ducks

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Abstract
Inactivated duck virus hepatitis (DVH) oil emulsion vaccines were prepared and evaluated in White Pekin breeder ducks and compared to a live DVH vaccine obtained from a commercial source. The response to vaccination was measured by serum neutralisation (SN) tests and resistance to experimental challenge in ducklings bred from vaccinated parents 32–35 weeks of age. Inactivated vaccines prepared from DVH virus grown in duck eggs stimulated a better antibody response than vaccines prepared from virus grown in chicken eggs. This was probably due to the higher yield of virus obtained from the duck eggs. Neither inactivated vaccine produced a satisfactory antibody response when used as a primary vaccine in 16‐week‐old ducks. Using the inactivated vaccine prepared from virus grown in duck eggs an improved antibody response was recorded when the vaccine was given in three doses at 8, 16 and 22 weeks of age. The levels of antibody in the breeding ducks was sufficiently high to confer protection to their progeny for up to 3 weeks of age. Ducks vaccinated at 2–3 days of age with the live DVH vaccine produced a high and sustained antibody response for up to 30 weeks. Ducklings bred from this group were resistant to challenge for up to 3 weeks of age. Ducks that were given live DVH vaccine at 2–3 days of age followed by inactivated vaccine at 22 weeks of age produced SN antibody levels significantly higher than levels produced from three doses of inactivated vaccine or one dose of live vaccine. Ducklings bred from these ducks were resistant to challenge for up to 3 weeks of age. These results suggest that inactivated DVH vaccines may be of value where the use of live DVH vaccines are contra‐indicated.