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Abstract
CASE HISTORY: Poor reproductive performance was observed in 62 dairy heifers, with a pregnancy rate of 23% following 57days 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.
Acknowledgements
The authors would like to thank laboratory staff and other members of the Incursion Investigation team at the Investigation and Diagnostic Centre (IDC) and Gribbles Veterinary for their contribution to this investigation, particularly Grant Munro, Della Orr, Elisa Sanderson, Taryrn Haydon, Maree Heikell; to the owners of the affected herds/farms who graciously complied with every request from the IDC; to Keith Thompson who carried out histopathology; and Alistair McDougall who conducted the initial investigation; to Falko Steinback, Trevor Drew and Cayla Beth McFadden for critically reviewing the manuscript. All funding for the project was provided as a part ofnormal foreign animal disease investigation carried out by theIDC.