Dermatitis in broilers caused by Escherichia coli: isolation of Escherichia coli from field cases, reproduction of the disease with Escherichia coli O78:K80 and conclusions under consideration of predisposing factors

A dermatitis in broiler chickens, especially on the caudal back, thighs and around the cloaca is observed more frequently in the last years. The skin is swollen at sites of inflammation and a fibrineous plaque extends between muscle and subcutis. No clinical signs are visible in the living flock but the disease causes economical losses because of degrading and rejection of carcasses. Studies of literature and own field observations suggest that Escherichia (E.) coli is involved in the development of the dermatitis. The following serotypes were isolated from field cases: O78:K80 (3X), O2:K56 (2X), O127:K63 (3X), O9:K57 (1X), O140 (2X); two isolates could not be identified. The reproduction of the dermatitis was successful by infection via feather follicles with E. coli O78:K80. The density of broilers kept on farms may contribute to the outbreak of dermatitis by violation of the skin followed by infection of the injuries. Massage of the infected sites by close contact of birds and insufficient hygiene may support the development of the disease.