A field investigation of causes of abortion in dairy cattle.

Cases of abortion on dairy farms on the Lancashire/Cumbria border were investigated by means of a systematic diagnostic procedure, using the facilities of a veterinary practice's laboratory, and the Ministry of Agriculture, Fisheries and Food veterinary investigation centre. Among approximately 3600 animals, 149 abortions were investigated on 54 farms in two years, an annual abortion rate of 2 per cent. A diagnosis was made in 34 per cent of the cases, based on a pathological examination of aborted material and bacteriological and serological findings. The most common pathogens associated with abortion were bovine viral diarrhoea virus (39 cases), bacterial or fungal infections (20 cases), infectious bovine rhinotracheitis virus (19 cases), and Leptospira hardjo (18 cases), either as single or multiple infections.