Blue Tongue in Sheep: A Systemic Review

Abstract

Bluetongue is a non-contagious disease of domestic and wild ruminants caused by a virus within the Orbivirus genus of the family Reoviridae and transmitted by Culicoides biting midges. All ruminants are susceptible to infection with bluetongue, but clinical disease is most often manifested in sheep. In cattle an im­portant role in the epidemiology of BTV because of prolonged viraemia.In past the endemic area of Bluetongue virus are world-wide within tropical and subtropical climates from approximately 35° S to 40° N, in accordance with the extension area of Culicoides imicola, which major vector of the virus in the “Old World, however, bluetongue has recently spread far beyond this traditional range. Since 2006 BTV serotype 8 has also been reported from the countries in Northern and Western Europe where Culicoides imicola has not been found. In such cases, BTV is transmitted by Palearctic biting midges, such as C. obsoletus or C. dewulfi. The economic losses due to direct losses are death, abortions and production loss and indirect losses are export restrictions of live animals and animal product.Anew strategy for prevention and control of the disease was developed to limit direct losses and to reduce indirect losses are the use of mass vaccination of all domestic ruminant species to limit the spread of BTV and the use of intensive active surveillance to limit spread. This reviewpresents comprehensive information on this dangerous disease including its history, spread, economic impact, modes of transmission and species effect, as well as the causative agent and pathogenesis,clinical sign, pathological change and diagnosis of the disease.It also deals with relevant preventive and control measures to be implemented in areas with endemic bluetongue outbreaks.

Keywords: Bluetongue, Culicoides, Orbivirus, Reoviridae