Haemophilus Infections in Chickens. IV. Results of Laboratory and Field Trials of Formalinized Bacterins for the Prevention of Disease Caused by Haemophilus gallinarum

Abstract

Bacterins of formalin-inactivated yolk-propagated cultures of Haemophilus gallinarum inoculated into young chickens stimulated a high degree of immunity to the development of gross air-sac lesions caused by H. gallinarum. Bacterin immunization also afforded protection against lowered egg production in hens exposed to H. gallinarum infection just prior to or during the egg laying period. A basic immunizing dose" of Haemo-philus bacterin was defined as the amount of bacterin containing at least 100 million Haemophilus organisms (and their by-products) that will immunize young chickens for 10 weeks against the development of gross air-sac lesions caused by natural exposure to H. gallinarum. Immunization of chickens with any or all of the known serotypes appeared equally effective in protecting them against disease caused by H. gallinarum.