Detection of bovine viral diarrhoea virus in specimens from cattle in South Africa and possible association with clinical disease.

Studies covering all aspects of bovine viral diarrhoea virus (BVDV) have been conducted in several countries in Europe, Asia and America. In southern Africa, more information is required about the nature of BVDV infection, the prevalence of different strains and the economic importance of the disease. The presence of BVDV in southern Africa has been known since the early 1970s through serological surveys but few reports confirming its presence by virus isolation and correlation with clinical disease are available. Specimens (n = 312) collected in 1998/99, from live and dead cattle from different farming systems, were obtained from private practitioners, feedlot consultants and abattoirs throughout the country. Specimens (n = 37) from African buffaloes (Syncerus caffer) in the Kruger National Park were also included. All specimens were processed for virus isolation in cell culture with confirmation by means of immunofluorescent antibody tests and some also by means of an antigen capture ELISA. BVDV was isolated from 15 (4.7%) cattle and were all noncytopathic biotypes. BVDV was not detected in 37 lymph nodes obtained from buffaloes in the Kruger National Park. Of the clinical signs in cattle from which virus were isolated, respiratory signs was the most frequent (10/15), followed by diarrhoea (5/15). Abortion, congenital malformations, haemorrhagic diarrhoea and poor growth were also included as criteria for selection of animals for specimen collection, but no BVD viruses were isolated from cattle manifesting these clinical signs.