Systemic Mycoplasma synoviae infection in 47-day-old broiler chickens with septicaemic lesions and increased carcass condemnation rate is reported. The clinical history included respiratory signs and an enlarged keel bursa. Condemnations at the processing plant were due to airsacculitis and keel bursitis. Involvement of several organs, including the keel bursa, liver, spleen, brain, choroid of the eye, nerves and skeletal muscle associated with vasculitis, and the isolation of M. synoviae from

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... he liver and keel bursa are only occasionally seen in field cases. Random amplified polymorphic DNA analysis of the M. synoviae isolated from the broiler chickens in this study had a different pattern when compared with the reference M. synoviae strains, WVU-1853, MS-H and F10-2AS, and another M. synoviae isolated from broiler breeders from the same company, but had a similar DNA pattern to an M. synoviae isolated from broiler chickens and turkeys owned by the same company. This finding suggests a horizontally acquired infection rather than vertical transmission.