However, the choice of this starting date implies introduction of BTV-8 in 2006. Possible routes of BTV-8 introduction into the original epicentre of the epidemic in northern Europe were investigated from 1 January 2006 through 18 August 2006 but the exact route of the introduction remained unknown. In the past, several retrospective and proactive studies have been successfully conducted to determine the first occurrence of an emerging infectious disease (EID) in a country (e.g., transmissible spongiform encephalopathies and bovine parafiliariosis), but limited studies have been carried out on the incursion of BTV-8 into northern Europe (e.g., ). Moreover, a longitudinal study of clinical BT cases in cattle indicated that photosensitization-like lesions may occur at a late stage in BT suspected and subsequently confirmed cases. In late June, Belgian veterinarians saw an unusual number of bovine cases that they primarily attributed to photosensitization or exposure to mycotoxins (sporidesmins), entities that could be included in the differential diagnosis of BT. Retrospective preliminary reports on the first observed BTV outbreaks in Belgium and Germany indicate that the first BTV clinical signs appeared around 17 July to 5 August 2006 (, ). The presumptive earliest date when clinical signs were observed was on the 30–31 July 2006 in The Netherlands. įew and limited data concerning the date of real introduction of BTV-8 in the northern European epicentre are currently published. While clinical surveillance underestimated the true impact of the epidemic (lack of sensitivity) it indicated the correct spatial trend. In addition, most evidence of the emerging disease was detected clinically, in the first instance, by veterinary practitioners. This preliminary investigation was confirmed by a seroprevalence survey of BTV-8 in cattle in the Netherlands in spring 2007 and was supported by Belgian findings. In northern Europe in 2006, statistical analysis based on 79.2% of first outbreaks notified before 15 September 2006, showed that the first significant disease cluster (epicentre) was located in The Netherlands, south of Maastricht (border area with Belgium and Germany) and had a 20 km radius. The third is through the active flight of infected vector Culicoides (local propagation) and the fourth is through passive flight of infected vector Culicoides by the wind (responsible for long-distance dissemination). The second is by infected vector Culicoides carried by various living (plants, animals) or inanimate (airplanes, ships) means. The first is through movement of viraemic animals (domestic and wild ruminants) or animal germplasm (semen, embryos). Ĭurrently, introduction of BTV from one area to another is thought to be able to occur in four ways. Whilst the full animal welfare and economic costs have not yet been fully quantified at the European level but some national studies are available such as the financial consequences of the Dutch bluetongue serotype 8 epidemics in 20. The great majority of the outbreaks was detected in four countries: France, Germany, Belgium and the Netherlands. Indeed, in 2007, the BTV8 expanded its range to include several European countries, involving at the end of the period: Belgium, Czech Republic, Denmark, France, Germany, Luxemburg, the Netherlands, Switzerland and United Kingdom. In contrast to 2006 when the virus was identified on some 2000 holdings, more than 40,000 of ruminant holdings became affected in 2007 with many infected animals exhibiting disease ( Animal Disease Notification System, ). In 2007, following a brief winter halt to its transmission, the virus re-emerged after overwintering via an unidentified mechanism in the previously infected areas. įirstly notified at 17 August 2006, BTV-8, thought to be of possible sub-Saharan origin, initiated an epidemic of BT in northern Europe (mainly The Netherlands, Belgium, and Germany) –. BTV belongs to the family Reoviridae, genus Orbivirus and exists as 24 serotypes. Bluetongue (BT) is an infectious but non contagious viral disease caused by bluetongue virus (BTV).
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