Pathogenicity of the border disease agent for the bovine foetus.

SUMMARY Ten pregnant heifers were inoculated intramuscularly at 50–51 days gestation with an emulsion of tissues from lambs affected with ovine Border Disease (BD); the same inoculum was used to inject 24 pregnant ewes at 25–40 days gestation. Six of the cows aborted between 117 and 264 days gestation and three more showed evidence of foetal death between 117 and 176 days; only one produced a live healthy calf at term. All the bovine foetuses showed severe growth retardation, and in three there was gross bilaterally symmetrical cavitation of the cerebrum. All the cows developed antibodies to bovine virus diarrhoea virus. It is concluded that the BD agent could be a potentially serious cause of reproductive failure in cattle which merits further investigation.