Mannheimia haemolytica

Formerly known as:

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; Peritonitis in sheep and Permeability types of pulmonary oedema. 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.