Multiplex RT-PCR amplification for Rift Valley Fever virus (RVFV), bluetongue virus (BTV), rinderpest virus (RPV), and Peste des petits ruminants virus (PPRV) in 10% oral mucosal homogenate. M, 50-bp DNA molecular weight marker (50-bp DNA ladder; Gene Direx); lane Mix, four viruses in a single-tube; lane Btv, BTV strain IND2003/01(serotype 2); lane Pprv, PPRV strain Nigeria 75/1; lane Rvfv, RVFV strain Smithburn; lane Rpv, RPV strain LATC; lane Neg, 10% oral mucosal homogenate collected from asymptomatic cattle.