Serological screaning of chickens of various ages and different localaties in area of Upper Egypt revealed high incidence of M. Synoviae infection. M. Synoviae was isolated from trachea, air-sacs, joints and yolk. The organism was identified biochemically and serologically by FA test. The recovered isolates of (MS) were highly pathogenic to chicken embryos causing 75% mortality and characterstic lesions in embroys.
Also it was pathogenic to one day old chicks when experimentally infected through tracheal and Foot-pad inoculation. Characterstic sym ptoms and lesions were observed with 4 weeks observation period, antibodies were detected as early as few days (PI) by RSA.