Evaluation of Inactivated Newcastle Disease Oil-Emulsion Vaccines

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Abstract
Three commercial European inactivated oil-emulsion (OE) vaccines and a USA-licensed inactivated Al(OH)3 vaccine were evaluated by primary vaccination of susceptible broilers and by secondary vaccination of layers previously immunized with live virus. A commercial live-virus vaccine was also used as a primary and secondary vaccine control. Evaluation was based on the hemagglutination-inhibition (HI) response and protection against challenge with neurotropic or viscerotropic velogenic Newcastle disease virus (NDV). OE vaccines induced higher and generally more sustained HI antibody titers than Al(OH)3 or live vaccines. With 1 exception, all challenged OE vaccinates were protected against clinical disease, a drop in egg production and a decrease in egg quality. Vaccination did not prevent infection with the challenge viruses; the infection rates were lowest in LaSota vaccinates and highest in Al(OH)3 vaccinates.