Correlation of humoral immunity to Pasteurella multocida in ducks and passive mouse protection

Abstract

Correlation-regression analysis was made between humoral antibody levels against crude capsular polysaccharide antigen tested by indirect haemagglutination (IHA) test on duck sera collected after vaccination with Pasteurella multocida A: 1 vaccine and the rates of passive protection of mice against
homologous challenge with 50 LD₅₀ (716 viable cells). The rates of protection of mice by sera collected from ducks before vaccination, 94 days after 1 vaccination and 70 days after 2 vaccinations were, respectively, 1/20 (5%), 7 /8 (87.5%) and 8/8 (100%) for pooled sera and 3/44 (6.82%), 13/18 (72.22%) and 16/19 (84.21 %) for individual sera. The IHA titres were significantly higher for vaccinated over unvaccinated, and for twice vaccinated over once vaccinated ducks. There was a significantly high correlation betwccn IHA Litres and rates of protection of mice.