Malignant catarrhal fever (MCF) is a serious, often fatal, disease that affects many species in the order Artiodactyla (even-toed ungulates) including cattle, bison, deer, moose, exotic ruminants and pigs. At least ten MCF viruses have been recognized, including two well-known viruses carried by sheep and wildebeest. Six of these viruses have been linked to disease, while the others have been found, to date, only in asymptomatic carriers. Each MCF virus is highly adapted to its usual host, and does not normally cause disease in that species, but can cause fatal infections if transmitted to susceptible animals.

Malignant catarrhal fever occurs in many countries worldwide. Sheep-associated MCF is the predominant form outside Africa. It is a particular problem in species such as farmed bison, deer and Bali cattle, although it occasionally affects relatively resistant hosts such as pigs and European breeds of cattle. Wildebeest associated MCF is an important disease among cattle in Africa, while zoos can be affected by either of these two forms, as well as by less common MCF viruses carried in various exotic ruminants. Malignant catarrhal fever is difficult to control, as the infections are widespread and asymptomatic in the reservoir species, and the incubation period can be long in susceptible animals. The only reliable methods of control are to separate susceptible species from carriers or breed virus-free reservoir hosts.