Until 1998 Europe was essentially bluetongue-free apart from Cyprus; but, since 1998 at least one serotype of Bluetongue Virus has been active on the continent every year (click here for a review). A summary of the various incursions of Bluetongue virus into Europe from 1998 to 2007 can be found on http://www.reoviridae.org/dsRNA_virus_proteins/ReoID/BTV-mol-epidem.htm.
Click here for the official European Commission pages on BTV control which contain the most up to date data on the restriciton zones
1998 to 2005
BTV-9 emerges on the Greek islands of Rhodes, Leros, Kos and Samos in 1998 and spreads north through the Greek mainaland, to Bulgaria and European Turkey and by 2002 had spread through the Balkan states as far as Albania and Bosnia & Herzegovina. At this time BTV-1, -4 and -16 are also reported in Greece - serotypes 4 and 16 were known to be circulating in the region to the east of greece (Turkey/Israel/Middle East), but BTV-1 was new to the region (Mellor et al., 2009b). In 2002 serotypes 9 and 16 are also detected in Italy (presumably spreading from the outbreaks occuring in the Balkans, Greece and Turkey) (Giovannini et al., 2004), and by the end of 2004 serotype 16 had been detected as far west as Corsica (Mellor et al., 2009b).
From the end of 1999 BTV serotype 2 was present in Tunisia, and by the end of 2000 had been detected in Algeria and Morocco. In mid-2000 BTV serotype 2 was detected in Sardinia and, by the end of the year, had spread to Corsica, the Balearic Islands, Sicily and southern mainland Italy (Mellor et al., 2009b).
Late in 2003 serotype 4 appeared in the islands of Menorca, Sardinia and in southern Corsica. In 2004 serotype 4 appears in Northwest Morocco during August, in October in southern mainland Spain (Andalucia and Extramadura) and the enclave of Ceuta and in November in Portugal on the Spanish border. During 2004 serotype 4 also spread into mainland Italy, meaning that by the end of the yearserotypes 2, 4, 9 and 16 in various combinations could be found throughtout Italy from Sicily to Tuscany (Mellor et al., 2009b).
The Bluetongue outbreaks in Europe from 1998 to 2005 spread to at least 16 Mediterranean countries (including France, Italy, Bulgaria, Macedonia, Yugoslavia, Bosnia, Albania, Croatia and Tunisia which were previously unaffected by Bluetongue). By 2005 more 1 million sheep had died and it had spread as far north as 44°50'N, making it the largest and most northerly spreading outbreak (Purse et al., 2005).
In 2006 BTV jumped even further north (a more detailed description below) and appeared in NW europe (northern France, Belgium, The Netherlands, Luxembourg and Germany) . Where it overwintered and then spread to affect UK, Denmark and the Czech Republic. This outbreak spread as far north as 53°N (Mellor et al., 2009a).
In August 2006, Dutch authorities reported the first ever case of bluetongue in Northern Europe (OIE & ProMED-mail). From work performed at the Institute for Animal Health at Pirbright, by the Arbovirus Research Group and the Community Reference Laboratory for bluetongue virus (BTV), the outbreak virus was rapidly identified as serotype 8 at the European Union Reference Laboratory at Pirbright. It subsequently spread to over 2,000 herds, mostly in the Netherlands, Belgium and Germany with a handful of cases in France and Luxembourg before transmission ceased in the winter. The route by which the virus was introduced into northern Europe remains unknown.
A more detailed analysis of the BTV-8 outbreak in 2006 is available from EFSA, while a retorspective epidemiological study published in 2010 placed the intial time and location of the BTV-8 introduction to be during spring 2006 near to the National Park of Hautes Fagnes and Eifel (Saegerman et al., 2010) (ProMED-mail)
On the 13th of June, a sentinel animal on a holding in North Rhein-Westphalia was announced to have displayed evidence of infection with bluetongue virus (BTV) serotype 8 during April. This was the first indication that the virus strain responsible for the outbreak in northern Europe last year had successfully overwintered in the region. The virus subsequently resurfaced in all countries affected in 2006, with new cases occurring for the first time in Denmark (OIE & ProMED-mail) and Switzerland (OIE & ProMED-mail), and the Czech Republic (OIE & ProMED-mail), as well as the UK (OIE & ProMED-mail).
On 22nd January, post-import testing indicated that a number of dairy cattle imported from the Netherlands into Northern Ireland had become PCR-positive since importation. Although these events are more fully described in the publication below, in brief they suggest that the strain of BTV-8 currently active in northern Europe may be able to cross the placenta and infect the foetus (as well as the possibility of oral infection). This may help to explain its ability to survive the relatively cold winters in northern Europe; see this Pirbright publication for a critical review of other potential mechanisms.
In 2008 BTV-8 has re-emerged across much of its previous range, and has continued to spread rapidly in some areas – particularly France, which had almost 30,000 cases by October (data available on the OIE website). Belgium, France, Germany, Luxembourg, the Netherlands and Switzerland have declared to OIE that they now consider BTV-8 to be endemic within their countries. The presence of BTV-8 has also been confirmed for the first time in Italy (OIE) in March and Sweden (OIE & ProMED-mail) and Hungary (OIE, SCFCAH report & ProMED-mail) in September, while surveillance zones now include parts of Poland and Romania.
Several companies have also started production of a vaccine against BTV-8, and most countries affected by the virus have since begun national vaccination campaigns.
Other bluetongue serotypes have also been detected. BTV-1 has continued to spread north since its detection in Morocco in 2006. Its range now overlaps significantly with that of BTV-8 in France and Spain.
On 24th October, the Arbovirus Research Group and EU Reference Laboratory for Bluetongue at IAH Pirbright confirmed the presence of BTV-6 in the Netherlands. In October and November the Netherlands and Germany reported laboratory findings of BTV-6 circulation in cattle located in neighbouring parts of their territories. Information on the genetic sequence available from the virus isolates indicated a high similarity with the BTV-6 South African modified live vaccine and investigations suggest that no virulent BTV-6 virus strain circulated in the Netherlands or Germany.
Swiss authorities have detected an entirely new type of bluetongue-like virus in goats. The virus was initially called Toggenburg Orbivirus (TOV), but based on genetic analysis, its finders have proposed that it should be classified as a new serotype of bluetongue, bringing the total number of serotypes known to 25 (Hofmann et al., 2008).
Also in February BTV-11 infected cattle were discovered in 8 farms in provinces of Flemish Brabant, Antwerp and Limburg, Belgium. Following investigations it was decided that this was an escape of a non-virulent African vaccine strain similar to the outbreak of BTV-6 in The Netherlands/Germany late in 2008.
The French Ministry of Agriculture announced in April the first French outbreak of BTV-1 in 2009 in the Department of Haute-Saone (French-German border) in an alpaca.
Following successful vaccination programmes across Europe the numbers of BTV cases dropped siginifcantly since the 2008 peak. By the begining of November 2010 the number of BTV cases across Europe (serotypes 1, 2, 4, 8, 9 & 16) totaled:
No cases of BTV-8 reported in northern and western Europe throughout 2010. Thus the UK to changed from a BTV Restriction Zone to a Low Risk Zone for BTV-8 in June 2010 (ProMED-mail and SCFCAH report), while in November Denmark was declared as a Low Risk Zone. Hungary was declared free from BTV in October, while in December Sweden and Denmark & Norway declared Bluetongue free status as of December and early 2011 respectively.
Reports to the EC in indicated that BTV-1 is circulating in the Extramadura and Andalusia regions of Spain and in western Portugal and BTV-16 (detection by surveillance, not clinical disease) in Greece and Cyprus (ProMED-mail and SCFCAH report). While in October BTV-4 appeared in Andalucia, Spain. Likely sources of these outbreaks include outbreaks of BTV-1 and BTV-4 in Algeria and Morocco and BTV-16 in Turkey.
After two years without any cases of Bluetongue Norway was declared BTV-free in April. In July the UK was declared as BTV-free (ProMED-mail and SCFCAH report) and the Czech Republic lifted BTV-restrictions in November. The Netherlands reached the minimum requirements to declare BTV-free status, but did not declare BTV-status to be able to perform vaccination against BTV-8 (due to trade of animals with member states still under restriction).
Spain reported BTV-1 in Plasencia (Caceres province, Extremadura) (ProMED-mail and SCFCAH report). BTV-1 was detected in the Extramadura and Andalusia areas of Spain in 2010, so this could be indicative of overwintering or BTV-1 being endemic. BTV-1 was also reported as ciruclating in Portugal. In December Cyprus reported to the EC that BTV-4 was also circulating, as well as the previously detected BTV-16.
Belgium, The Nertherlands, Germany and Luxembourg lift BTV restirictions on 15th February 2012 (SCFCAH report and ProMED-mail). In June Jersey lifted it's restriction zone for BTV-1 and BTV-8 and France (excluding Corsica) in December (SCFCAH report and ProMED-mail).
Italy is beleived to have BTV-2, BTV-9 and BTV-16 circulating and in October reported an outbreak of BTV-1 in Sardinia (assumed to be introduced by BTV-infected culicoides midges crossing from Algeria/Tunisia).
Spain reported BTV-14 in an animal imported from Poland (late 2011) and Lithuania (2012) . Later in 2012 BTV-14 was confirmed in samples from Poland, Estonia, Lithuania and Latvia. The EC concluded, on the mbasis of the information available (the absence of clinical signs, the genotype of the misolates being homologous to the vaccine reference strain (as indicated by the EU Reference Laboratory for bluetongue) and the low intra-herd seropositivity reported, the affected Member States were facing a vaccine incident and not an outbreak of Bluetongue. The BTV-14 was also detected in Finland and Russia in late 2011 and early 2012.
Elsewhere in Europe Greece continues to have outbreaks of BTV-4 (possibly related to nearby outbreaks in Israel and Palestine) and BTV-16 and Spain & Portugal BTV-1 and BTV-4 (data availaible from the OIE)
Sardinia continues to suffer from outbreaks of BTV-4 and BTV-1, which has spread to the Italian mainland along coast from Tuscany to Lazio (SCFCAH report, ProMED-mail reports 1, 2). BTV-1 also appeared in Corsica (possibly a spread from nearby Sardinia) (SCFCAH report and ProMED-mail).
On the Iberian Peninsula BTV-4 reappears in South Portugal and Soutwest Spain , and BTV-1 in a limited area in the center of Spain. While BTV-4 and BTV-16 continue to be seen on Greek Islands close to the Turkish Coast. While BTV outbreaks continue to be reported from other countries around the Mediterrean basin- Libya and Lebanon.
In 2014 BTV-1 and BTV-4 continue to be a problem in Spain and Italy. Bluetongue appeared in Cyprus in late December, and was deteremined to be BTV-16 by the European Union Reference Laboratory at Pirbright.
In May a potential new serotype (putatively BTV-27) was isolated from goats in Corsica. Sequence analysis of this strain has shown the serotypes with the closest sequenes to be BTV-25 (73% nucleotides, 75% amino acids) and BTV-26 (65% nucleotides, 60% amino acids) (Jenckel et al., 2015).
BTV8 in France, Aug 2015 - Jan 2017
In November it was reported that, with 95% of the genome sequenced, the strain showed full homology to the strain circulating in 2007 in Northern Europe. It is possible that the disease may have been circulating at a very low level in wildlife and it is only when vector numbers reached a high level and herd immunity dropped below a threshold, that disease was able to circulate in livestock again.
The BTV-4 outbreak in the Balkan region had not spread to any new territories since Croatia in November 2014, suddenly spread to Austria (ProMED-mail) and Slovenia (ProMED-mail) in November 2015. The outbreak in Austria was detected through a surveillance programme in place since September 2014 due to outbreaks in Hungary (presentation to SCPAFF). Likewise the Slovenian outbreak was detected by a national Bluetongue surveillance program, and was confirmed and serotyped at Pirbright (presentation to SCPAFF).
BTV 8 outbreaks continued in France during 2016, with more than 400 outbreaks being recorded by October (presentation to SCPAFF). Outbreaks in March expanded the restriction zone in the south and Northwest of the country, to the northeast in April and September and in November further to the northeast.
An outbreak of BTV in the Larnaca region of Cyprus in September was confirmed as BTV8 by the EURL for Bluetongue. This is a new serotype for Cyprus (currently covered by a restriction zone for serotypes 4 and 16) (presentation to SCPAFF, ProMED-mail).
BTV 4 continued to be reported in the eastern Europe, Spain and Italy. In September a new outbreak of BTV4 was reported in the previously BTV4-free region of Veneto in the North of Italy (ProMed Mail Post) and spread westward across the north of Italy (presentation to SCPAFF). No outbreaks of BTV4 have been reported in Portugal since November 2013 and Portugal plans to declare freedom from BTV4 in December 2016 (presentation to SCPAFF).
Giovannini A, Calistri P, Conte A, Savini L, Nannini D, Patta C, Santucci U and Caporale V (2004) Bluetongue surveillance in a newly infected area. Vet. Ital. 40, 188–97.
Hofmann MA, Renzullo S, Mader M, Chaignat V, Worwa G and Thuer B (2008). Genetic characterization of Toggenburg orbivirus, a new bluetongue virus, from goats, Switzerland. Emerging Infectious Diseases, 14(12), 1855-61. DOI: 10.3201/eid1412.080818 [pdf]
Mellor PS, Baylis M, & Mertens PPC (2009a). Introduction. In Mellor PS, Baylis M, & Mertens PPC (Eds.), Bluetongue (1 ed., pp. 1-6). London: Academic Press.
Mellor PS, Carpenter S, Harrup L, Baylis M, Wilson A and Mertens PPC (2009b). Bluetongue in Europe and the Mediterranean Basin. In Mellor PS, Baylis M, & Mertens PPC (Eds.), Bluetongue (1 ed., pp. 235-264). London: Academic Press.
Purse BV, Mellor PS, Rogers DJ, Samuel AR, Mertens PPC and Baylis M (2005) Climate change and the recent emergence of bluetongue in Europe. Nat. Rev. Microbiol. 3, 171–81.
Saegerman C, Mellor P, Uyttenhoef A, Hanon J-B, Kirschvink N, Haubruge E, Delcroix P, Houtain J-Y, Pourquier P, Vandenbussche F, Verheyden B, De Clercq K and Czaplicki G (2010). The Most Likely Time and Place of Introduction of BTV8 into Belgian Ruminants. PLoS One 5(2): Article No: e9405. DOI: 10.1371/journal.pone.0009405 [pdf]
Jenckel M, Breard E, Schulz C, Sailleau C, Viarouge C, Hoffmann B, Hoper D, Beer M and Zientara S (2015). Complete coding genome sequence of putative novel bluetongue virus serotype 27, Genome Announcements 3(2). DOI:10.1128/genomeA.00016-15 [pdf]