SEVERE DISEASE IN ADULT DAIRY-CATTLE IN 3 UK DAIRY HERDS ASSOCIATED WITH BVD VIRUS-INFECTION

During 1993 outbreaks of diarrhoea in adult dairy cows in three geogra phically unrelated herds were found to be caused by bovine viral diarr hoea virus (BVDV). The affected animals showed signs of acute watery d iarrhoea, agalactia and pyrexia (39.4 to 42 degrees C). Ulceration of the buccal mucosa, a mucoid nasal discharge and stiffness were inconsi stent signs. The disease spread rapidly in each case. The diagnosis wa s confirmed by the isolation of non-cytopathic BVDV from blood and tis sues and by the demonstration of significantly rising titres to BVDV b y an ELISA. The highest morbidity recorded was 40 per cent with one he rd experiencing a 10 per cent mortality. There was no increased incide nce of abortion in any of the herds, either at the time of or subseque nt to the outbreaks of diarrhoea. In one herd the purchase of a persis tently viraemic heifer 14 days before the outbreak was thought to be t he source of infection, but in the other two herds the source was not established.