An outbreak of avian colibacillosis was diagnosed on a broiler farm in Lusaka, Zambia. There were 12 open flat pens on the farm, and chicks in house No.6, which had more than four thousands birds, showed respiratory signs, general weakness and diarrhea from 33 days of age, and 565 chicks died by 50 days of age. Severe airsacculitis, pericarditis and perihepatitis were odserved.
Escherichia coli was isolated from the affected chicks. Serologically, the chicks were negative for
Mycoplasma gallisepticum and
M. synoviae. Etiological survey revealed that 4, 446 chicks were introduced into the pen, even though the capacity was 3, 500 birds. Therefore, density of the pen reached 18.3 birds/m
2. In conclusion, the present outbreak seemed to be caused by overcrowding of birds. Key Words: avian colibacillosis, overcrowding, Zambia.
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