Malignant catarrhal fever (MCF): An emerging threat
Barkha Sharma, Singh Parul, Gourab Basak and Raghvendra Mishra
Malignant Catarrhal fever is a highly infectious and often fatal viral disease of animals of family Bovidae and Cervidae in the order Artiodactyla. MCFV is group of at least 10 gamma herpesviruses belonging to Genus Macavirus in the subfamiliy Gammaherpesvirinae, of which two viruses viz., Alcelaphine Herpesvirus -1 (AlHV-1) causing Wildebeest associated MCF (WA-MCF) and Ovine Herpes Virus -2 (OvHV-2) causing Sheep associated MCF (SA-MCF) are potentially pathogenic. These viruses remain asymptomatic in their natural Hosts wildbeests and sheep, respectively, but cause severe clinical disease in susceptible animals which are terminal/dead end hosts. MCFV is found worldwide wherever clinically susceptible hosts are found in the vicinity of inapparent wildlife carriers. The WA-MCF is a problem in African countries, threatening the conservation of dwindling wildebeest populations in these countries along with a major cause of tremendous economic losses to the livestock farmers in terms of increased veterinary cost, deaths and income lost due to annual migration of cattle during the breeding season of wildebeests to avoid the disease. SA-MCF is mainly an emerging disease of domestic animals, captive ruminants and wildlife outside Africa including India. Till now, clinical findings in susceptible species and histopathology was the main stay for the diagnosis but now serology is the method of choice. Competitive ELISA is a preferred test for the screening of infection in susceptible animals. Several multiplex PCRs have been validated to simultaneously detect and differentiate MCFVs OvHV-2, CpHV-2, MCFV-WTD, MCFV-ibex and AlHV-1 with high sensitivity. Various vaccine candidates for AlHV-1 have been tested upon for last sixty years but hitherto, no effective commercial vaccine is available. As the disease is continuously spreading, a lot still needs to be understood regarding its transmission, epidemiology and ecology. Thus, there is a lot of scope for detailed studies and improved methods for better and prompt diagnostic methods, control and prevention.