Clinical responses and reproductive outcomes in pregnant ewes experimentally infected with bovine viral diarrhoea virus (type-1c) between days 59 and 69 of gestation

Low lambing rates and the birth of persistently infected (PI) lambs have previously been recorded in sheep infected with BVDV. However, there is little information available in regards to the clinical profile of acute BVDV infections in sheep. As a result the aim of this study was to investigate the clinical, haematological and reproductive responses in pregnant ewes infected with the predominant Australian BVDV strain, BVDV-1c. Twenty-two pregnant ewes were experimentally inoculated with serum derived from a BVDV PI cattle serum between 59 and 69 days gestation. A further 11 pregnant ewes were left uninfected. No clinical changes were observed in the inoculated ewe group although a mild leukopaenia and a prolonged decrease in eosinophil counts was detected. Severe foetal losses, physical and neurological abnormalities in lambs and the birth of a persistently infected lamb was also recorded in the inoculated ewe group. Results from this study suggest that acute BVDV-1c infections in sheep are clinically in-apparent, unless infection occurs in a pregnant flock, where severe reproductive losses can be seen at lambing. To eliminate the reproductive losses associated with BVDV infection close contact between sheep and cattle, of unknown BVDV status, should be avoided during the joining and pregnancy periods.