Natural transmission of bovine viral diarrhoea virus-1c from a persistently infected neonate lamb to naïve sheep and cattle.

This study investigated the transmission of bovine viral diarrhoea virus (BVDV)-1c from a persistently infected (PI) neonate lamb to naïve sheep and cattle using three treatment groups: four naïve ewes and their five lambs, which were copaddocked with the PI lamb; five steers, which were housed in a paddock adjacent to the PI lamb; and five steers, which had direct but limited exposure to the PI lamb. Serum samples were collected and tested for BVDV-specific antibodies. Serum samples from the PI lamb, from day of birth to eight weeks of age, were tested for BVDV-specific antibodies and antigen and submitted for quantitative PCR to determine the viral load present at each week of age. Only one lamb from the copaddocked group developed BVDV-specific antibodies following comingling while all the steers in both the cattle treatment groups remained BVDV antibody negative. Quantitative PCR results from the PI lamb showed lower viral loads from day of birth to six weeks of age, compared with the results at seven and eight weeks of age. This may reflect maternal colostral BVDV antibody concentrations in the neonate lamb or other viral properties.