the invention is directed to a method of detecting infection of a blood sample by various strains of bovine diarrhoea virus including a first test wherein anti - bovine diarrhoea virus antibodies are detected by means of a recombinant antigen comprising the bvd p80 protein expressed by a eukaryotic host and a second test wherein viral particles are detected by means of antibodies directed against the bvd p80 viral protein . the method is particularly useful in detecting pathogenic conditions such as persistent viremias and acute infections caused by bvd viruses , and is particularly advantageous because it is an extremely sensitive and efficient test and because it is capable of detecting infections caused by any one of a wide variety of bvd strains . the recombinant antigen employed in the method is preferably encoded by the nucleotide sequence listed as seq id no : 1 .