The role of Mannheimia haemolytica in bovine respiratory disease (BRD)

Bovine respiratory disease, or BRD, causes substantial economic losses through both direct effects on livestock and the indirect costs of treatment and prevention. It is a multifactorial disease caused by a range of bacterial and/or viral pathogens; however, Mannheimia haemolytica is commonly isolated from cattle with BRD.

Despite the widespread use of antibiotics and vaccination, BRD remains a challenge. This may reflect the negative effects of environmental stressors, such as transportation, or underlying infections such as bovine respiratory syncytial virus on the immune systems of cattle.

Mannheimia haemolytica is associated with a number of virulence factors, such as leukotoxins and a lipopolysaccharide cell wall, which enable it to infect the lung and contribute to BRD.