The incidence of MCF is usually sporadic.
Morbidity is low, but mortality is high.
In the sheep-associated form, cases tend to recur on the same premise over many years, particularly if the sheep or source animal is not removed. In the alcelaphine form of MCF, the virus in the adult reservoir animal is cell associated and thus rarely shed. The Masai believe that cattle become infected when they have contact with placenta from a wildebeest. Virus has not been detected in the placenta, but free virus has been found in the lacrimal and nasal secretion, feces, and hair follicles of neonatal wildebeest from 4 days to 4 months of age. Passively acquired antibody does not prevent viral replication.