Characterisation of African isolates of rinderpest virus.

Isolates of rinderpest virus (RPV) recovered from outbreaks of the disease in Kenya and Southern Sudan between 1986 and 1993 were compared to each other and to earlier isolates from East and West Africa. The recent isolates were mildly pathogenic for susceptible cattle and thus resembled other mild strains of RPV recovered from cattle and wildlife in East Africa more than 30 years ago. Monoclonal antibody analysis using a panel of 12 anti-RPV haemagglutinin protein-specific antibodies (mAbs) revealed that individual isolates were distinguishable. However, the panel of mAbs could not be used to relate the isolates on the basis of their pathogenicity or geographic origin. Immunoprecipitation of the virus-induced proteins from infected Vero cells, followed by SDS-polyacrylamide gel electrophoresis, showed that the recent mild RPV isolates from eastern Africa were closely related to each other and to their contemporary isolates from Nigeria and Egypt, but they were distinct from another mild isolate recovered from the region three decades ago. Two distinct lineages of African RPV isolates were identified by sequencing a region of the genome around the proteolytic enzyme cleavage site of the fusion protein from the old and new isolates. One lineage, which included virus isolates recovered from East and West Africa during the 1960s, showed a closer phylogenetic relationship to Asian and Middle Eastern RPV isolates. The other lineage consisted mainly of isolates recovered from East, West and North Africa between 1983 and 1993. The results showed that there was co-circulation of two different lineages of RPV in Nigeria during the epizootics of the 1980s.