Bordetella avium: an opportunistic pathogen in Leghorn chickens.

Experiments were conducted in order to produce bordetellosis in specific-pathogen-free (SPF) leghorn chickens. In the first and second of three experiments, young turkeys and chickens, respectively, were allotted into groups and challenged at 2 weeks of age with one of seven different isolates of Bordetella avium and two isolates of B. avium-like bacteria. Isolates of B. avium with the smooth colony type were pathogenic in turkeys but not in chickens. The B. avium-like bacteria and B. avium isolates with rough colonial morphology were nonpathogenic. In the third experiment, SPF leghorn chicks were vaccinated at 1 day of age with infectious bronchitis virus, Newcastle disease virus, or both and then challenged with B. avium at 7 days of age. Chickens vaccinated and then challenged with B. avium showed clinical signs and lesions similar to bordetellosis in turkeys. No clinical signs were observed in unchallenged chickens. Thus, we conclude that B. avium is an opportunistic pathogen in SPF leghorn chickens.