Bluetongue (BT) | Anses - Agence nationale de sécurité sanitaire de l’alimentation, de l’environnement et du travail

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French Agency for Food, Environmental and Occupational Health & Safety

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Updated on 04/08/2016

Bluetongue (BT)

Presentation and situation in France

Keywords : Bluetongue, Animal diseases, Animal health

Bluetongue (BT) is a viral disease transmitted from one infected animal to another by the bite of a midge of the genus Culicoides (arbovirosis). It mainly affects sheep, but can also manifest in cattle, goats and wild ruminants. A purely animal disease, bluetongue does not affect humans and has no impact on food quality. Causing retarded growth in affected animals, the death of some and abortions in infected females, this disease causes significant economic losses for farmers. Control measures, in particular vaccination, which is the most effective tool, are also costly. The characteristics of this disease are given below.

The virus responsible for BT is an Orbivirus from the Reoviridae family. There are 26 different types of this virus known as serotypes. They are differentiated on the basis of their antigenic properties, i.e. their ability to induce an immune response and to be recognised by a specific antibody.

Initially found in Africa, BT has gradually been spreading northwards over the past few decades, probably due to global warming and international trade. Indeed, the transmission of this disease and its geographical extension are closely associated with the presence of populations of biting midges called Culicoides that are this disease’s vectors, and whose development is favoured by higher temperatures. After an initial incursion into Europe in the late 1950s, in the south of Spain and Portugal, BT affected Greece in 1979 and again in 1998, before appearing in Italy and France (Corsica) in 2000. The disease is now present on all continents except Antarctica.

2006 – 2010: A major animal epidemic in north-west Europe

In 2006, an epidemic of bluetongue caused by serotype 8 (BTV-8) affected north-west Europe. It was the first documented epidemic of bluetongue in northern Europe and the first time circulation of serotype 8 had been identified on the continent. Five countries were affected: Germany, Belgium, France, Luxembourg and the Netherlands. In total, about 2000 outbreaks were reported in 2006, including six in France.

After a winter lull due to vector inactivity, a massive resurgence of the epidemic was observed from the beginning of July 2007. More than 50,000 BTV-8 outbreaks were identified in this year in nine European countries: Germany, Belgium, Denmark, France, Luxembourg, Netherlands, Switzerland, Czech Republic and the United Kingdom.
Only slightly affected in the summer of 2006, France was confronted with an epidemic of a completely different magnitude in 2007, with more than 15,000 BTV-8 outbreaks spread over a very large area in the northern half of the country. The epidemic front progressed mainly in the direction north-east to south-west.

In addition, a new serotype, BTV-1, originating from Spain, appeared on the French mainland at the end of 2007, causing three outbreaks in south west France.

The epidemic peak caused by serotype 8 was observed in France in 2008 (whereas the peak in northern Europe had been in October 2007). Its circulation resumed in spring 2008, heading south and west in France and causing more than 27,000 outbreaks.
The circulation of serotype 1 also resumed in France in 2008, causing nearly 5000 outbreaks in the south-west and in Brittany.

Alongside the health measures implemented, campaigns of mandatory immunisation, using inactivated virus vaccines against serotypes 1 and 8, were implemented on the French mainland in spring 2008, until autumn 2010. During these campaigns, funded by the state, more than 120 million doses of vaccine were distributed. Vaccination became optional and payable by farmers in late 2010. The positive impact of the vaccination, coupled with the acquisition of protective immunity following infection, led to a collapse in the number of outbreaks: less than a hundred in 2009, one in 2010, and none in 2011.

The health situation has gradually improved throughout Northern Europe, enabling the UK to regain its BT disease free status in 2011, followed by Germany, Belgium and the Netherlands in 2012.
In France, the last outbreak of bluetongue was identified in June 2010, in the département of Alpes-Maritimes (serotype 1).
In southern Europe, the virus was still circulating in 2011, with outbreaks being reported in Spain (serotype 1), Portugal (serotype 1), Italy (serotypes 1, 2, 8 and 9), Greece (serotypes 4 and 16) and Cyprus (serotypes 4 and 16).

Mobilisation of research resources for bluetongue in France

Given the extent to which farmers were exposed to the epidemic, ANSES, together with the French Animal Health Network (RFSA), deemed it necessary and urgent to undertake operational studies and research to respond, in a short timeframe, to the needs of the professional sectors and risk managers.

ANSES was therefore asked by the State to coordinate this programme based on efficient cooperation between research institutes, higher education institutions, professional organisations and farming institutes. This programme (the BT programme), mainly funded by the Directorate General for Food (DGAL), was based on national teams and European partnerships.