Comparison of the Efficacy of Mycoplasma gallisepticum Vaccine Programs in Chickens.

ABSTRACTThe efficacy of two Mycoplasma gallisepticum commercially available vaccines administered singly or in combination was evaluated in two trials; in both trials, specific-pathogen-free (SPF) chickens were vaccinated with the live attenuated F-strain vaccine at 5 weeks of age (WOA), an inactivated M. gallisepticum bacterin at 9 and 13 WOA, or both vaccines. In the first trial, groups of vaccinated birds, along with controls, were challenged via aerosol with virulent R-strain at 22 and 41 weeks of age. All of the vaccine programs evaluated showed a statistically significant reduction in colonization with the challenge strain following challenge at either timepoint. However, only the programs including the live vaccine also showed significant protection from respiratory lesions and ovarian regression; and although there were numerical differences indicating benefits of a combined (live + bacterin) program, the addition of bacterins did not enhance (or reduce) the efficacy of the F-strain vaccine in a statistically significant manner (P ≤ 0.05). In the second trial, groups of vaccinated birds, along with controls, were challenged via aerosol with different doses of virulent M. gallisepticum R-strain at 17 weeks of age. Both vaccination programs in this trial (live only and live + bacterin) resulted in significant protection against challenge strain colonization and air sac lesions (P ≤ 0.05); In addition, the live + bacterin program showed significantly improved results with respect to colonization with the challenge strain as well as protection from air sac lesions compared to the live vaccine alone (P ≤ 0.05).