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Open Access Review

Bluetongue: a historical and epidemiological perspective with the emphasis on South Africa

Peter Coetzee13*, Maria Stokstad3, Estelle H Venter1, Mette Myrmel2 and Moritz Van Vuuren1

Author Affiliations

1 Department of Veterinary Tropical Diseases, Faculty of Veterinary Medicine, University of Pretoria, Private Bag X04, Onderstepoort, Pretoria 0110, South Africa

2 Department of Food Safety and Infection Biology, Norwegian School of Veterinary Science, P. O. Box 8146, Oslo, Norway

3 Department of Production Animal Clinical Sciences, Norwegian School of Veterinary Science, P. O. Box 8146, 0033 Oslo, Norway

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Virology Journal 2012, 9:198  doi:10.1186/1743-422X-9-198

Published: 13 September 2012

Abstract

Bluetongue (BT) is a non-contagious, infectious, arthropod transmitted viral disease of domestic and wild ruminants that is caused by the bluetongue virus (BTV), the prototype member of the Orbivirus genus in the family Reoviridae. Bluetongue was first described in South Africa, where it has probably been endemic in wild ruminants since antiquity. Since its discovery BT has had a major impact on sheep breeders in the country and has therefore been a key focus of research at the Onderstepoort Veterinary Research Institute in Pretoria, South Africa. Several key discoveries were made at this Institute, including the demonstration that the aetiological agent of BT was a dsRNA virus that is transmitted by Culicoides midges and that multiple BTV serotypes circulate in nature. It is currently recognized that BT is endemic throughout most of South Africa and 22 of the 26 known serotypes have been detected in the region. Multiple serotypes circulate each vector season with the occurrence of different serotypes depending largely on herd-immunity. Indigenous sheep breeds, cattle and wild ruminants are frequently infected but rarely demonstrate clinical signs, whereas improved European sheep breeds are most susceptible. The immunization of susceptible sheep remains the most effective and practical control measure against BT. In order to protect sheep against multiple circulating serotypes, three pentavalent attenuated vaccines have been developed. Despite the proven efficacy of these vaccines in protecting sheep against the disease, several disadvantages are associated with their use in the field.

Keywords:
Bluetongue virus; Culicoides; Serotype; Survey; African carnivores; African herbivores; Sheep; Cattle; Onderstepoort; South Africa; Control; Vaccine