Mycoplasma gallisepticum and M. synoviae in Breeding Flocks and Drug Sensitivity of Their Field Isolates

Mycoplasma gallisepticum (MG) and M. synoviae (MS) infection were examined in 157 flocks, which consisted of 60 egg-type breeder flocks (E) on 20 farms in 16 prefectures and 97 meat-type breeder flocks (M) on 43 farms in 21 prefectures, over a period of 1978 through 1982.At 60 weeks of age, MG- and MS-positive percentage were 55% and 73.3%, respectively in E and 67% and 74.2% in M. MG- and MS-free flocks were converted frequently to be serologically positive by 20 to 30 weeks of age. The MG strains isolated were highly sensitive to DOTC, OTC, TC and PZ, but 26%(9/35) of them were resistant to EM, OM, SP and TS. The MS strains isolated were also highly sensitive to DOTC, OTC, TC and TS, but poorly sensitive to the other drugs. It was suggested that the medication of tetracycline antibiotics might be required for MG and MS elimination.