Competitive virus assay method for titration of noncytopathogenic bovine viral diarrhea viruses (END+ and END− viruses)

► We developed a new assay method for non-cytopathogenic bovine viral diarrhea virus. ► It was named as competitive virus assay method (CVA method). ► It is based on the principle of interference and exaltation of Newcastle disease virus. ► It is secure biologically and applied to not only titration but also discrimination. ► The results of titration show the same value as it of conventional methods.