Mannheimia haemolytica

Also known as: Pasteurella haemolytica — M. haemolytica


Mannheimia haemolytica is a species of the Mannheimia genus. It is the cause of epizootic pneumonia in cattle known as Shipping Fever, Transit Fever or pneumonic pasteurellosis. 90% is caused by Mannheimia haemolytica Biotype A, serotype 1 but also Pasteurella multocida. It is usually secondary to viral infections such as parainfluenza - 3 or IBR, bacterial infections such as Mycoplasma or environmental stress.

M. haemolytica may contribute to Enzootic pneumonia of calves; Enzootic pneumonia of lambs and peritonitis in sheep. It also causes gangrenous mastitis in sheep.

M. haemolytica is beta-haemolytic on blood agar and grows weakly on MacConkey agar. It is odourless. All are Mannheimia A biotypes and the strains often produce a cytotoxin, known as leukotoxin, which kills leukocytes of ruminants. Leukotoxin is a member of the RTX group toxins, and is probably largely responsible for the pathogenicity of the bacteria in septicaemia and pneumonia.

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