Effect of temperature-sensitive Mycoplasma gallisepticum vaccine preparations and routes of inoculation on resistance of white leghorns to challenge.

One-week-old chickens were vaccinated with live or formalin-killed temperature-sensitive (TS) Mycoplasma gallisepticum (MG) either intranasally (IN) or subcutaneously (SQ). Live TS MG protected chickens against S6 strain challenge directly into the air sacs, regardless of route of vaccination. Killed MG, however, protected chickens only when administered SQ. Antibody to MG was detected in sera and in the tracheal and air-sac washings of only the chickens given live vaccine IN. The antibody present in tracheal and air-sac washings may be one of the mechanisms that play a role in resistance to MG challenge.