(A) Specific amplification, performed with primers α and β, of DNA from milk cell fractions of milk coming from PBMC PCR-positive cows and producing a 2,538-bp product. Lanes 1 to 7 correspond to milk cell fraction samples; lanes − and + correspond to negative and positive controls respectively. 1 kb, molecular size marker. (B) Ethidium bromide-stained gel of HindIII-digested 2,538-bp BoHV-4 amplified sequence from PBMC DNA samples (2, 3, and 6). 1 kb, molecular size marker.