Sheep associated malignant catarrhal fever: an emerging disease of bovids in India

Malignant catarrhal fever (MCF) is a fatal lymphoproliferative disease affecting bovids, cervids and other ruminant species caused by viruses belonging to subfamily Gammaherpesvirinae, genus Macavirus. Among the 10 MCF viruses known to cause the disease, alcelaphine herpesvirus 1 (AlHV-1) and ovine herpesvirus 2 (OvHV-2) are the two most widely prevalent causative organisms. The AlHV-1 naturally infects wildebeest and causes wildebeest associated MCF (WA-MCF) in cattle in regions of African sub-continent. The OvHV-2 is prevalent in all varieties of domestic sheep as a sub-clinical infection and causes sheep associated MCF (SA-MCF) in susceptible ruminants in most regions of the world. In India, the detection of cases of SA-MCF in cattle and OvHV-2 infection in sheep during the last decade has established the presence of the virus in native sheep of the country. The present review presents up to date information on various aspects of SA-MCF and its causative agent OvHV-2 with special reference to Indian scenario.