Bluetongue in Europe

Bluetongue is a devastating disease of ruminants caused by a virus that is spread by Culicoides biting midges. Until ten years ago, Europe was essentially bluetongue-free apart from Cyprus; but, since 1998 at least one serotype of bluetongue virus (BTV) has been active on the continent every year (click here for a review). The current known distribution of BTV in Europe is shown here (last updated 2008-10-10)

For details of current movement restrictions in the UK, please see the Defra website.

The 2006 epidemic

In August 2006, Dutch authorities reported the first ever case of bluetongue in Northern Europe (ProMED-mail report 20060818.2311). 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. It subsequently spread to over 2,000 herds, mostly in the Netherlands, Belgium and Germany with a handful of cases in France and Luxembourg (see map (PDF)) 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

 

The 2007 re-emergence

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 (ProMED-mail report 20070613.1928). 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 (ProMED-mail report 20071013.3360) and Switzerland (ProMED-mail report 20071028.3504), and the Czech Republic (first case 26th November; see OIE report (PDF)), as well as the UK.

Arrival in the UK

On Friday 21st September 2007, a veterinarian spotted suspicious clinical signs in a cow on a holding near Ipswich. Samples taken from the animal were tested at IAH within 24 hours and were found to be positive for BTV-8. Testing of other animals on the site began immediately, and on Monday 24th September, a second cow at the same holding was found to be positive, as reported by Defra. Defra announced on the 28th 2007of September that it believed BTV to be circulating locally within East Anglia.

Bluetongue in Europe in 2008

On 22 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 [7] 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 recent IAH publication for a critical review of other potential mechanisms.

This year, BTV-8 has re-emerged across much of its previous range, and has continued to spread rapidly in some areas – particularly France, which had over 15,000 new cases by 1st October (link (PDF)). 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 Sweden (in September; see OIE report), Hungary (in September; see SCFCAH report (PDF)), and Italy (see OIE report), 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. More recently, 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 (as shown on this map; last updated 2008-11-07). Meanwhile, on 24 October, the Arbovirus Research Group and EU reference laboratory at IAH Pirbright confirmed the presence of BTV-6 in the Netherlands. Finally, 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. Further information can be found in this article (PDF).

For more information or to discuss media usage of images, please email iah.bluetongue@bbsrc.ac.uk. If you are a media representative and would like to conduct an interview on bluetongue or other exotic insect-borne diseases, please contact our press office.

Further information

The current known distribution of BTV in Europe is shown here (last updated 2008-10-10).

Research on bluetongue at IAH

The Institute for Animal Health is an important centre for bluetongue epidemiology research in Europe. Institute researchers were the first to isolate bluetongue virus in a midge other than the African vector Culicoides imicola in 1979 [1] and also to identify the risk that, with the expansion of C. imicola into Europe, the virus could establish itself in new vector species, drastically increasing its range [2]. Institute researchers also first proposed that infected midges could be transported for long distances on wind currents [3], a mechanism which is now receiving renewed attention.

More recently, collaborative work between the Institute and TALA Research (Oxford University) has provided strong evidence of the role of climate change in the expansion of bluetongue within Europe since 1998 [4], and the Institute has also performed extensive theoretical work on the mechanisms by which climate may be affecting transmission [5]. Institute researchers also recently described a novel mechanism for the virus to conceal itself within host immune cells [6], which may offer some insight into the puzzling ability of the virus to reappear in areas after long period of absence and without any apparent reintroduction event.

The Institute for Animal Health and its collaborators are currently investigating aspects of bluetongue transmission and risk in several ongoing projects, using techniques from field collections and laboratory experiments to computer modelling and satellite imagery. Current collaborators include Oxford University, Advanced Pest Solutions (Edinburgh University), Aberdeen University, Cambridge University, and the Met Office.

Genetic analyses of bluetongue virus isolates from around the world (http://www.reoviridae.org/dsRNA_virus_proteins/ReoID/BTV-isolates.htm) have provided a database that can be used to help identify the strain and origins of novel bluetongue viruses more rapidly and more accurately than ever before (Maan et al 2007). These studies allowed us to develop molecular typing assays (Mertens et al 2008; http://www.reoviridae.org/dsRNA_virus_proteins/ReoID/BTV-S2-Primers-Eurotypes.htm). that were used in the first identification of BTV type1 in North Africa (2006), BTV type 8 in northern Europe and the UK (2006 & 2007) and BTV type 6 in the Netherlands (2008)

International Reference Laboratory

IAH Pirbright is an International Reference Laboratory for bluetongue, and provides diagnostic services to the European Community (EC), the World Animal Health Organisation (OIE), and the Food and Agriculture Organization (FAO). In our capacity as European Community Reference Laboratory for bluetongue, we also carry out annual inter-laboratory proficiency tests for all the National EC bluetongue reference labs [8, 9]. The Institute is working closely with several authorities, including other national reference laboratories, Defra, and the European Food Safety Authority, and on the current outbreak.

References in the text:

  • Mellor, P. S. & Pitzolis, G. (1979) "Observations on breeding sites and light-trap collections of Culicoides during an outbreak of bluetongue in Cyprus" Bulletin of Entomological Research 69(2): 229-234.
  • Mellor, P. S. & Boorman, J. (1995) "The transmission and geographical spread of African Horse Sickness and bluetongue viruses" Annals of Tropical Medicine and Parasitology 89(1): 1-15.
  • Sellers, R. F., Pedgeley, D.E., et al (1978) "Possible windborne spread of bluetongue to Portugal, June-July 1956" Journal of Hygiene 81(2): 189-196.
  • Purse, B. V., Mellor, P. S., et al (2005) "Climate change and the recent emergence of bluetongue in Europe" Nature Reviews Microbiology 3: 171-181.
  • Wittman, E., & Baylis, M. (2000) "Climate change: effects on Culicoides-transmitted viruses and implications for the UK" The Veterinary Journal 160: 107-117.
  • Takamatsu, H., Mellor, P. S., et al (2003) "A possible overwintering mechanism for bluetongue virus in the absence of the insect vector" Journal of General Virology 84: 227-235.
  • Menzies FD, McCullough SJ, McKeown IM, Forster JL, Jess S, Batten C, Murchie AK, Gloster J, Fallows JG, Pelgrim W, Mellor PS, Oura CA.(2008) Evidence for transplacental and contact transmission of bluetongue virus in cattle. Veterinary Record 163(7): 203-209.
  • Batten, C.A., Bachanek-Bankowska, K., Bin-Tarif, A., Kgosana, L., Swain, A.J., Corteyn, M, Darpel, K., Mellor, P.S, Elliott, H.G. and Oura, C.A.L (2008) Bluetongue virus: European Community inter-laboratory comparison tests to evaluate ELISA and RT-PCR detection methods. Veterinary Microbiology, 129 (1-2): 80-88.
  • Batten, C.A, Swain, A.J., Bachanek-Bankowska, K., Bin-Tarif, A., Oura, C.A.L (2008). Bluetongue virus: European Community inter-laboratory comparison tests to evaluate ELISA and RT-PCR detection methods 2007. In press, Veterinary Microbiology.

Selected recent BTV publications by IAH and collaborators

  • Carpenter S, HL Lunt, D Arav, GJ Venter and PS Mellor (2006). Oral susceptibility to bluetongue virus of Culicoides (Diptera: Ceratopogonidae) from the United Kingdom. Journal of Medical Entomology 43(1): 73-78. [Abstract]
  • Carpenter S, Mellor PS, Torr SJ (2008) Control techniques for Culicoides biting midges and their application in the UK and northwestern Palaearctic. Medical and Veterinary Entomology 22(3): 175-187. [abstract]
  • Darpel KE, CA Batten, E Veronesi, AE Shaw, S Anthony, K Bachanek-Bankowska, L Kgosana, A bin-Tarif, S Carpenter, U Müller-Doblies, H Takamatsu, PS Mellor, PPC Mertens, and CAL Oura (2007) Clinical signs and pathology shown by British sheep and cattle infected with bluetongue virus serotype 8 derived from the 2006 outbreak in northern Europe. Veterinary Record 161(8): 253-261. [Abstract]
  • Gloster J, PS Mellor, L Burgin, C Sanders, and S Carpenter (2007) Will bluetongue come on the wind to the United Kingdom in 2007? Veterinary Record 160(13): 422-426. [Abstract]
  • Gubbins S, S Carpenter, M Baylis, JLN Wood, PS Mellor (2008). Assessing the risk of bluetongue to UK livestock: uncertainty and sensitivity analysis of a temperature-dependent model for the basic reproductive number. Journal of the Royal Society Interface, online 2007-07-17.[full text]
  • Maan S, Maan NS, Ross-Smith N, Batten CA, Shaw AE, Anthony SJ, Samuel AR, Darpel KE, Veronesi E, Oura CA, Singh KP, Nomikou K, Potgieter AC, Attoui H, van Rooij E, van Rijn P, De Clerq, K, Vandenbussche F, Zientara S Bréard E, Sailleau C, Beer M, Hoffman B, Mellor PS, Mertens PP (2008) Sequence analysis of bluetongue virus serotype 8 from the Netherlands 2006 and comparison to other European strains. Virology 377:308-318. [Abstract]
  • Purse BV, PS Mellor, DJ Rogers, AR Samuel, PPC Mertens and M Baylis (2005). Climate change and the recent emergence of bluetongue in Europe. Nature Reviews Microbiology 3(2): 171-181. [Abstract]
  • Shaw AE, P Monaghan, HO Alpar, S Anthony, KE Darpel, CA Batten, S Carpenter, H Jones, CAL Oura, DP King, H Elliot, PS Mellor, and PPC Mertens (2007) Development and validation of a real-time RT-PCR assay to detect genome bluetongue virus segment 1. Journal of Virological Methods 145, 115-26. [Abstract]
  • Wilson A, Darpel K, Mellor PS (2008) Where does bluetongue go in the winter? PLoS Biology 6(8): e210. [full text]
  • Wilson AJ, S Carpenter, J Gloster, and PS Mellor (2007) Re-emergence of bluetongue in northern Europe in 2007. Veterinary Record 161, 482-6. [Abstract]