Protection of Ducklings with a Broth-Grown Pasteurella anatipestifer Bacterin

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Abstract
P. anatipestifer (PA) serotypes 1, 2 and 5 grew to high densities in tryptic soy broth and tryptose broth (TB) when the media were continuously shaken or aerated. Growth in 100 ml to 15 l of TB exceeded an absorbance of 1.0 at a wavelength of 525 nm (.apprx. 0.7 for a 1/3 dilution), and contained > 1010 colony-forming units/ml. A bacterin was prepared from the 3 serotypes of PA grown in aerated TB. Two s.c. injections of this bacterin protected 70-85% of ducklings against experimental challenge with each of the 3 PA serotypes, which killed 90-100% of unimmunized controls. The bacterin could be diluted 1/5 without decreasing protection below 80%. Field studies on Long Island duck farms, in 1980 and 1981, demonstrated significant reductions in mortality with the use of the broth-grown PA bacterin.