Bluetongue control, a new challenge for Europe

March 2008

Bluetongue, its development and spread throughout Europe, and control strategies, were amongst the topics on the agenda at a recent symposium organised by the University of Liege with Prof Thiry and bluetongue vaccine manufacturer, Intervet/Schering Plough.

Experts from many European countries gathered in Brussels to reveal the scale of the infection and share their experiences and learnings from the northward spread of the bluetongue virus (BTV) seen over the past two years.

Until fairly recently considered an exotic disease, the rapid northward spread of bluetongue from southern Europe to endemic proportions was at the forefront of many delegates’ minds. The scale of the infection – more than 50,000 cases in the EU in 2007 – and the consequences for farmers in Belgium, The Netherlands, Germany and France were revealed. While there are different serotypes of the bluetongue disease, serotype 8 (that found in northern Europe) seems to be more virulent than others, causing high mortality and morbidity in sheep.  It is also more severe for cattle, leading to a drop in milk yield of up to 40% in some infected cows.

Attendees from bluetongue-affected countries all agreed that because vector transfer and livestock movements have both been implicated in the spread of the virus, vaccination and vector control, alongside enhanced biosecurity, were the most effective disease management strategies.

The rapid development of an inactivated vaccine by Intervet/Schering Plough (Bovilis BTV8), which should be available for use in May this year, should, according to the experts, see a considerable reduction in the number of new cases. The company has succeeded in developing and producing its vaccine in just two years, which is considerably less than the time such a complex process normally takes.

It was highlighted, using an example from Spain where disease eradication had been achieved, that at least 80% of susceptible species must be vaccinated. This could lead to eradication of the disease, but widespread compliance is critical; at least 80% of all farmed animals must be vaccinated, although nearer 100% is desirable as the wild animal population will also provide a possible source of virus for midges. Trial work from Germany has highlighted the ability of a deltamethrin-based insecticide (Butox 7.5 pour on – Intervet/Schering Plough) applied to the back of livestock to migrate to the areas favoured by midges (the legs and belly) and kill midges for up to 28 days after application. The work showed that the use of a deltamethrin insecticide is of value when combined with vaccination.

Click on above image for a full sized picture of the symposium participants