A correlativein vivostudy of the surface morphology and colonisation of the chicken trachea infected bymycoplasma gallisepticumstrains R and F

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Abstract
The pathogenic processes occurring in the chicken trachea as the result of infection by Mycoplasma gallisepticum were followed at frequent intervals over a 2‐week period after introduction of the organism into the trachea. A correlation was made between changes in the surface morphology of the trachea, as seen by the scanning electron microscope, and mycoplasma colonisation of the upper respiratory tract, as evaluated in isolation studies. Effects of the clinical status of the birds were indicated by measurements of weight gain and humoral serological responses. In the case of pathogenic R strain colonisation was accompanied by severe changes in the tracheal wall as well as depression in weight gain and marked serological response. On the other hand, M. gallisepticum F (a less pathogenic strain used for vaccination in laying hens) profusely colonised the trachea but produced only moderate oedematous changes in the tracheal wall. There were no significant effects on weight gain and apparently no serological response could be detected during the experiment following F strain infection.