title: History of Orbivirus research in South Africa.
abstract: In the early colonial history of South Africa, horses played an important role, both in general  transportation and in military operations. Frequent epidemics of African horsesickness (AHS)  in the 18th century therefore severely affected the economy. The first scientific research on the  disease was carried out by Alexander Edington (1892), the first government bacteriologist of  the Cape Colony, who resolved the existing confusion that reigned and established its identity  as a separate disease. Bluetongue (BT) was described for the first time by Duncan Hutcheon in  1880, although it was probably always endemic in wild ruminants and only became a problem  when highly susceptible Merino sheep were introduced to the Cape in the late 18th century.  The filterability of the AHS virus (AHSV) was demonstrated in 1900 by M'Fadyean in London,  and that of the BT virus (BTV) in 1905 by Theiler at Onderstepoort, thus proving the viral  nature of both agents. Theiler developed the first vaccines for both diseases at Onderstepoort.  Both vaccines consisted of infective blood followed by hyper-immune serum, and were  used for many years. Subsequent breakthroughs include the adaptation to propagation and  attenuation in embryonated eggs in the case of BTV and in mouse brains for AHSV. This  was followed by the discovery of multiple serotypes of both viruses, the transmission of  both by Culicoides midges and their eventual replication in cell cultures. Molecular studies  led to the discovery of the segmented double-stranded RNA genomes, thus proving their  genetic relationship and leading to their classification in a genus called Orbivirus.  Further  work included the molecular cloning of the genes of all the serotypes of both viruses and  clarification of their relationship to the viral proteins, which led to much improved diagnostic  techniques and eventually to the development of a recombinant vaccine, which unfortunately  has so far been unsuitable for mass production.
authors: University of Pretoria, South Africa. daan.verwoerd@up.ac.za
authors: Daniel W
authors: DW
authors: Verwoerd
mesh_terms: D000355:African Horse Sickness / Q000453:epidemiology / Q000266:history* / Q000517:prevention & control / Q000821:virology; D000818:Animals; D001819:Bluetongue / Q000453:epidemiology / Q000266:history* / Q000517:prevention & control / Q000821:virology; D002519:Ceratopogonidae / Q000821:virology; D049671:History, 18th Century; D049672:History, 19th Century; D049673:History, 20th Century; D006736:Horses; D007303:Insect Vectors / Q000821:virology; D051379:Mice; D018163:Orbivirus / Q000145:classification / Q000502:physiology / Q000648:ultrastructure; D012756:Sheep; D013019:South Africa / Q000453:epidemiology; D014765:Viral Vaccines / Q000266:history / Q000276:immunology; D014776:Virus Cultivation / Q000266:history
chemical_list: D014765:Viral Vaccines