RESUMO
CASE HISTORY: Poor reproductive performance was observed in 62 dairy heifers, with a pregnancy rate of 23% following 57 days mating with one 3-year-old and two 2-year old Belted Galloway bulls that were sourced from separate sheep and beef farms. CLINICAL FINDINGS: The 3-year-old bull was small for its age with small testes. This bull was seropositive for bovine viral diarrhoea virus type I (BVDV 1) using an Ag-ELISA, and positive on PCR for border disease virus (BDV). DIAGNOSTIC INVESTIGATION: Phylogenetic analysis of the BDV isolate from the affected bull indicated that it was part of the BDV 1 group. For 40 of the heifers exposed to the bull that were tested, all of them had a positive VNT (virus neutralisation test) titre to both BDV (titre≥1:4) and BVDV 1 (titre>1:4). On the farm of origin of the affected bull there was no evidence of BDV circulating between cattle. DIAGNOSIS: Persistent infection of a bull with BDV. CLINICAL RELEVANCE: Cattle persistently infected with BDV can act as a source of virus for infection of other cattle. The benefit of testing cattle for bovine viral diarrhoea could be enhanced by using tests that also detect BDV.
