EFFECT OF MIXED LIVE VACCINE (NEWCASTLE-DISEASE AND INFECTIOUS-BRONCHITIS) AND MYCOPLASMA-GALLISEPTICUM ON THE CHICKEN RESPIRATORY-TRACT AND ON ESCHERICHIA-COLI INFECTION

Interaction between mixed live vaccine (Newcastle disease and infectious bronchitis), Mycoplasma gallisepticum (MG) and Escherichia coli (EC) was studied in specific-pathogen-free chickens, aged 7 days, inoculated intranasally. In the tracheas of chickens inoculated with vaccine, MG and EC, profuse multiplication of EC occurred together with severe and persistent histological lesions, and some birds died from EC infection. Similar though less dramatic effects occurred in birds that received vaccine and EC. The tracheas of chickens inoculated with the vaccine alone, or with MG and EC, or with MG alone, showed comparatively mild effects. There were no histological lesions in the tracheas of chickens inoculated with EC alone. This study suggests that the field use of mixed live vaccine in flocks infected with MG may induce EC septicaemia. © 1994 Academic Press Limited.