Shipping fever is an infection caused by in cattle and sheep.
Shipping fever may also be caused by Mannheimia haemolytica, in the absence of , and M. haemolytica serovar A1 is known as the most common cause of the disease. The pathologic condition commonly arises where the causative organism becomes established by secondary infection, following a primary bacterial or viral infection, which may occur after stress, e.g. from handling or transport.