Bluetongue: a 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. It is a reportable disease of considerable socioeconomic concern and of major importance for the international trade of animals and animal products. In the past, bluetongue endemic areas were found between latitudes 40°N and 35°S; however, bluetongue has recently spread far beyond this traditional range. This is in accordance with the extension of areas in which the biting midge Culicoides imicola, the major vector of the virus in the “Old World”, is active. After 1998 new serotypes of bluetongue virus (BTV) were discovered in Southern European and Mediterranean countries. 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, and the disease has thus spread much further north than BTV has ever previously been detected. New BTV serotypes have recently been identified also in Israel, Australia and the USA. This review presents comprehensive information on this dangerous disease including its history, spread, routes of transmission and host range, as well as the causative agent and pathogenesis and diagnosis of the disease. It also deals with relevant preventive and control measures to be implemented in areas with bluetongue outbreaks.  

Retrospective Analysis of the Bluetongue Outbreak in Serbia

“…The presence and geographic distribution of Culicoides biting midges have proven to be critical aspects in BTV transmission among susceptible animals, and also the limiting factor in occurrence of the disease (3). Prior to 1998, the appearance of BTV infections were limited to a geographic band between the latitudes 40ºN and 35ºS, habitat of its main vector, C. imicola (14). The breaking point for emergence of bluetongue on the Balkans was the 1998 BTV outbreak on 4 Greek islands (30,31).…”

“…In cattle, goats and wild ruminants, bluetongue is most often present in a subclinical form or with mild or transient clinical signs (2,12). Occurrence of bluetongue is closely related with the activity of competent Culicoides vectors, thus the emergence of this disease was traditionally reported in a geographic band between the latitudes 40ºN and 35ºS, which is its natural habitat (14).…”

“…However, after nearly 20 years of absence BTV was recorded again on four Greek islands, where BTV-9 was isolated and that was the first report of this serotype on the European continent (15,16 (14,17,19). There have been indications that serotypes BTV-6 (detected in Germany and Holland) and BTV-11 (detected in Belgium) could have been introduced by illegal import of live attenuated vaccines (20,21), as no virus has been isolated and no clinical signs of bluetongue disease have been observed (22).…”

Bluetongue: Virus proteins and recent diagnostic approaches

“…It is characterized by high fever, catarrhal inflammation of the buccal and nasal mucous membranes, and inflammation of the tongue, intestine and sensitive laminae of the foot. Bluetongue has been known in South Africa for over a 100 years and endemic in wild ruminants since antiquity (Maclachlan et al, 2009, Maclachlan, 2011Sperlova and Zendulkova, 2011;Maan et al, 2012a;Bitew et al, 2013).…”

“…BT is a disease of ruminants in temperate zones. However, clinical disease is reported in tropical and subtropical areas of the world when nonnative breeds of ruminants are introduced in virus endemic area (Sperlova and Zendulkova, 2011). The European outbreaks of BT due to BTV-8 in 2006 have dramatically changed the geographic and ecological episystems around the world (Maclachlan, 2011;Maan et al, 2008).…”