The Thai Journal of Veterinary Medicine


The efficacy and safety of different live Mycoplasma gallisepticum (MG) vaccines were determined. One hundred and fifty six-week-old female layer chickens were equally divided into 6 groups. Groups 1-6 received F (two groups), 6/85 and ts-11 strains, positive and negative control, respectively. At 8 weeks old, 5 birds/group were sacrificed and gross thoracic airsac lesion scores (GTALS) and microscopic tracheal lesion scores (MTLS) were blindly evaluated. At 12 weeks old, groups 1-5 were challenged through an eye dropping with approximately 1x106 CFU of MG Thai isolated. At 13 and 14 weeks old, 10 birds/group were swabbed in the palatine fissure to isolate MG and further differentiate between the vaccine and MG Thai isolated by PCR and random amplified polymorphic DNA assays, respectively. At 14 and 16 weeks old, 10 birds/group were sacrificed and the degree of protection was evaluated by GTALS and MTLS. The results revealed that feed conversion rate during 6-12 and 12-14 weeks old ranged between 4.33-7.53 and 5.88-15.18, respectively. At 12 and 14 weeks old, the vaccinated groups had antibody determined by serum plate agglutination (SPA), only groups 1 and 2 being detected by ELISA. Only SPA could detect antibody response in group 5 at 14 weeks old. GTALS and MTLS at 8, 14 and 16 weeks old ranged from 0 and 0.05-1.80, 0-0.3 and 0.13-1.38, and 0.15-1.65 and 0.38-2.28, respectively. At 12 weeks old, the MG DNA of the vaccine strains was detected in groups 1, 2 and 4, whereas MG DNA of MG Thai isolated was detected in groups 3, 4 and 5 at 13 weeks old and in groups 2, 3, 4 and 5 at 14 weeks old. The F strain had good results in safety, growth performance, protection and re-isolation of the F strain from vaccinated birds followed by ts-11 and 6/85 strains, respectively.

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