Immunopotency of novel oil adjuvant vaccines employing Pasteurella multocida biofilm and capsule enhanced organisms in ducklings

Abstract

Pasteurella multocida-a gram-negative bacterium with a broad host range and ubiquitous distribution—is a serious problem in ducks, and the best method of control is vaccination with locally prevalent strains. The present study was conducted to compare the immunopotency of vaccines employing P. multocida biofilms and capsule enhanced organisms with ordinary broth grown organisms in 1-month-old ducklings, by measuring the humoral immune response and the protection conferred by each vaccine during homologous challenge with virulent organisms. Formalin inactivated oil adjuvant bacterin vaccines were prepared from Pasteurella multocida A: 1. They were grown in conventional broth, capsule enhancement medium, and under biofilm mode. Four different groups of birds were vaccinated with the respective vaccines by intramuscular route, and the immunopotency of the vaccines was assessed by employing passive haemagglutination (PHA) and homologous challenging with virulent organisms. The PHA titres obtained for the biofilm vaccine group on day 14 postvaccination were much higher than those for the other 2 groups. They also provided 10% more protection when challenged with 200 and 100 median "lethal dose" doses. The capsule enhanced vaccine and conventional bacterin revealed similar results.