The mortality rate in symptomatic animals is 90 to 100 percent. Treatment is supportive only. Factors There are many factors that can increase the chances of infection or affect the severity of an outbreak. The number of animals in the herd, population density and species of the susceptible hosts are huge factors. Other factors include closeness of contact and amount of virus available for transmission. Diagnosis Diagnosis of BMCF depends on a combination of history and symptoms, histopathology and detection in the blood or tissues of viral antibodies by ELISA or of viral DNA by PCR. The characteristic histologic lesions of MCF are lymphocytic arteritis with necrosis of the blood vessel wall and the presence of large T lymphocytes mixed with other cells. The similarity of MCF clinical signs to other enteric diseases, for example blue tongue, mucosal disease and foot and mouth make laboratory diagnosis of MCF important. The world organisation for animal health recognises histopathology as the definitive diagnostic test, but laboratories have adopted other approaches with recent developments in molecular virology. No vaccine has as yet been developed. AlHV-1 and OvHV-2 are almost indistinguishable without molecular sequencing. However Anderson et al 2008 do find some usable differences, mostly necrosis or lack of necrosis, and lymphoid accumulation. Life cycle Infection of T cells is typical of MCF group viruses. This was discovered by Nelson et al 2010 by experimental infection of Bison bison with ovine strains. They additionally found B lymphocytes to be present but irrelevant in MCF lesions. Ovine Ovine strains have been investigated by Meier-Trummer et al 2009 (OvHV-2 experimentally in rabbit) and Nelson et al 2013 (SA-MCF experimentally in Bison bison), both finding these to be lytic viruses. Bovine Bison Bison bison are found by Nelson et al 2010 to suffer widespread mucosal necrosis but rarely occlusive thrombosis, and they judge thrombosis to be hardly able to explain the incidences of necrosis. Nelson also find CD8 and CD3 to be the most common immune cell types in lesions. Bos CD8 and CD4 are the most common immune cell types in lesions found by Nelson et al 2010. Prognosis Bovine malignant catarrhal fever usually is fatal in susceptible species like cattle and bison, and any animal that survives will remain infectious for the rest of its life even if it shows no subsequent signs of the disease. Such survivors may relapse and suffer attacks in later