The possibility of bluetongue occurring in the Mediterranean region has been recognised since the epizootic in Cyprus during 1943. The disease has occurred sporadically in the region since then, involving relatively short lived epizootics, usually caused by a single virus serotype.
Although bluetongue was not generally considered as enzootic in the Mediterranean region prior to 1998, there is evidence that it has persisted in some places for many years and there is serological evidence for a range of different BTV types in eastern Turkey and the Near East. In 1998, a wave of bluetongue epidemics broke into the European region from the eastern Mediterranean countries and Near-East (involving BTV types 1, 4, 9 and 16) reaching as far west as the Italian peninsula, with BTV-9 spreading north into Bulgaria and the Balkan region. In 1999, there was another incursion into Europe from Maghreb (involving BTV-2), which reached Sicily, mainland Italy, Sardinia, Corsica and the Balearic islands in 2000. Between 2000 and 2003, many of these areas were still affected but without dramatic changes in disease distribution. However, in 2003 and 2004 a distinct strain of BTV-4 (from the one isolated in eastern and central Mediterranean area) reached Sardinia, Corsica and the Balearic Islands.
In 2004 Morocco and then continental Spain declared outbreaks of bluetongue (caused by the same strain of BTV-4), suggesting a third route of entry into Europe from Morocco. These outbreaks continued in the Iberian Peninsula into 2005 and there was evidence that the South African vaccine strains of BTV-2 and BTV-16 used in the central Mediterranean region were transmitted in the field. Since, in summer 2006, outbreaks due to a new strain (BTV8) have been reported in Belgium, Germany, Netherlands and France in the absence of C imicola .
African Horse Sickness virus (AHSV), which has the same vectors ( Culicoides imicola ) as bluetongue virus (BTV) has been absent from the Mediterranean region and Europe since the outbreaks in Iberia 1987 to 1991. The distribution and abundance of Culicoides imicola is still increasing in Southern Europe and there is evidence that adults of other Culicoides species ( C. obsoletus and C. pulicaris groups – which are abundant and widespread across central and northern Europe) have become involved in the transmission of BTV. The introduction of at least 6 different strains of BTV into Europe over the last eight years, via three different routes, suggests that the risks of further introductions of these viruses has greatly increased and remains at an elevated level. The changes in vector capacity within Europe (which may be related to climate change) have vastly increased the risks and potential for economic losses, that would be caused by an outbreak of AHS in the region.
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