The isolation and characterization of bovine viral diarrhoea viruses from cattle in South Africa

Abstract

A limited number of scientific publications dealing with aspects of BVDV infection have emanated from southern Africa. This study describes the isolation of BVD viruses, gene sequence analysis of the 5' non-translated region (5' NTR) of the genome, the generation of phylogenetic data of local strains and the recording of clinical signs associated with each isolate. Specimens (n=352) collected during 1998-1999, from live and dead animals from different farming systems, were obtained from private practitioners, feedlot consultants and abattoirs throughout the country. Specimens from buffaloes (cerus caffer the Kruger National Park were included as specimens from dead animals. Three cell lines and 200 tubes of pooled foetal bovine sera were also processed. Standard cell culture techniques to isolate virus were followed. Techniques designed to detect BVDV antigen or nucleic acid such as antigen capture enzyme-linked immunosorbent assay and polymerase chain reaction, were used on blood, organs and cell lines. The indirect fluorescent antibody test was used for antibody detection. Twenty-five isolates from cattle were confirmed as BVDV with PCR and after analysis of the 5'NTR, the most conserved part of the genome, a phylogenetic tree was constructed. All strains were noncytopathic and were identified as BVDV I, either BVDV Ia (NADL-like) or BVDV Ic or BVDV I* subgroups. BVDV was not detected in 37 lymph nodes obtained from 37 buffaloes in the Kruger National Park. Of the clinical signs in cattle from which virus was isolated, pyrexia and respiratory distress was the most frequent (46,7%), followed by pyrexia and diarrhoea (20%), respiratory disease without pyrexia (20%) and diarrhoea without pyrexia (13,3%). Abortion, congenital malformations, haemorrhagic syndrome and poor growth were also included as criteria for selection of animals for specimen collection.