MCF is caused by two different herpes viruses, one found in wildebeest (alcelaphine herpesvirus-1) as the reservoir host and one found in sheep (ovine herpesvirus-2) as the reservoir host. The reservoir hosts are unaffected by the virus but serve as a source of infection for cattle and other susceptible species (deer, bison, buffalo, pigs).
The wildebeest virus can cause severe and fatal infection in cattle and is restricted to Africa and other areas where wildebeest may be found. It is not present in Australia. Ovine herpesvirus-2 is present in sheep around the world as an inapparent infection and this virus is present in Australia.
In susceptible animals MCF viruses cause systemic infection with catarrhal inflammation of mucosal epithelium and vasculitis.
Bos taurus and Bos indicus cattle are more resistant to infection with the sheep-associated virus than some other breeds such as Bali cattle, and than deer. Clinical disease in Bos taurus and Bos indicus cattle due to sheep-associated MCF is rare.
The disease in cattle due to infection with ovine herpesvirus-2 is usually sporadic and involves single animals, though it can give rise to outbreaks. Clincal signs can vary widely ranging from the acute form, when minimal changes are observed prior to death, to overt cases showing high fever, bilateral corneal opacity, profuse catarrhal discharges from the eye and nose, necrosis of the muzzle and erosion of the buccal epithelium.
Confirmation of MCF requires laboratory testing of blood to detect antibodies and histology on tissue samples.
Differential diagnoses include bovine viral diarrhoea virus and infectious bovine rhinotracheitis.
There is no treatment for the viral infection. General supportive and nursing care may be useful for less severely affected animals.
Control. The primary method of control is based on segregation of highly susceptible animals from the reservoir host. Since clinical disease in most commercial cattle breeds in Australia is rare, segregation of sheep and cattle is not normally practiced.