Kinetics of serum and local haemagglutination inhibition antibodies in chicks following vaccination and experimental infection with Newcastle disease virus and their relation with immunity

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Abstract
Broiler chicks were vaccinated against Newcastle disease (ND) by nebuli‐sation of live La Sota vaccine, or by intramuscular administration of inactivated oil emulsion vaccine. Local haemagglutination inhibition (HI) antibodies were detected in spray vaccinated chicks but not in those vaccinated intramuscularly. Initially local HI‐titres in trachea, tears and saliva behaved in the same way as the serum HI‐titre, but after maximum levels were reached approximately 10 days after vaccination, local HI‐titres waned to levels that were no longer detectable after 4 weeks. Challenge exposure with velogenic Newcastle disease virus (NDV), showed that high post‐vaccinal serum HI‐titres were correlated with complete resistance to clinical disease but not to infection, as indicated by the prevention of virus multiplication in the trachea and also by the post‐challenge serum HI‐titres. Resistance to infection was only detected in spray vaccinated chicks. No relation was found between local HI‐titres and resistance to experimental infection with velogenic NDV.
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