Natural resolution of air sac lesions caused by mycoplasma meleagridis in turkeys.

Lesions caused by Mycoplasma meleagridis were followed in one hatch of turkeys from one day to 20(1/2) weeks of age. Air sac lesion incidence increased from 20% at one day to 44% at six weeks of age with a slow decline to 10% at 10 weeks of age. Lesions were detectable on careful examination at 10-20% level to 20 weeks of age on laboratory examination, but at 20(1/2) weeks only 0.07% lesions were found in 1000 turkeys from the same hatch. Air sac lesion severity, based on an arbitrary 0.5,1,2,3,+scale, increased in intensity and spread of air sac involvement from a mean of 1.5 at day old to 2.5 at five weeks of age. This declined to 1.0 at 10 weeks of age and lesions became progressively more faint until careful examination was necessary to detect them in birds 15 weeks and older. The latter would not be considered as a cause of total condemnation. The percentage of Mycoplasma isolations from the respiratory tissues were much higher in birds exhibiting air sac lesions than those in which no typical air sac lesions were visible, as follows. air sacs 51.6 vs. 2.9, lungs 43.3 vs. 4.0, trachea 47.2 vs. 4.6, sinus 38.5 vs. 19.0.