Rachel Hebditch

An outbreak of Bluetongue virus in Europe has meant that animal movements have been banned or restricted in large areas of the Netherlands, Belgium, Germany and France. New cases have been reported in western Belgium that would push the 150km surveillance zone into the UK. However the European Commission has confirmed that there is no need to establish additional measures to cover UK at this stage. The Commission explained that the UK authorities are familiar with the current disease situation and are taking the necessary precautions. The Commission emphasised that if there are further outbreaks of bluetongue in western Belgium the commission may review the UK’s status.

So far there have been 136 outbreaks in the Netherlands, 177 in Belgium, 144 in Germany and four in France.

The European Union has adopted safeguard measures in all these countries including the whole of Luxembourg even though no cases have been detected there. EU rules require a standstill zone of 20km in radius from infected premises, a protection zone of 100km and a surveillance zone of 150km. This is a significant development as the virus has not previously been reported in areas beyond 50  North, latitude.

Alarmingly scientists at the Institute for Animal Health’s Pirbright Laboratory in the UK have shown that the bluetongue virus causing the disease in Europe is serotype 8 that has not been previously identified in Europe. Typing of the virus is important in tracking where the BTV-8 virus came from and the results show that this one is not descended from the vaccine forms that have been used in many parts of southern Europe. The gene sequence points to an origin in sub-Saharan Africa.

Bluetongue disease is spread by a biting midge. Both males and females feed on nectar, however the females also need to feed on blood to enable their eggs to mature. They feed on the blood of an infected animal and then go on to feed on another animal spreading the virus in the process.

It is mainly a disease of sheep but other ruminants are susceptible. It is characterised by a fever and swelling of the lips, mouth, nasal linings and eyelids. Animals can lose condition rapidly and some may die. There is no treatment for bluetongue. Prevention is possible by vaccination and by controlling midge populations but neither is totally successful.

Several years ago bluetongue spread from Africa, Asia and the southernmost tips of Europe further northwards into Spain and Italy. This was due to the northwards spread of the species of midge Culicoides imicola that had previously been limited to Africa and Asia. Scientists at the Institute for Animal Health have shown that two other species of biting midges Culicoides obsoletus and Culicoides pulicaris, which are common in central and northern Europe, including the UK, are also able to spread the virus and are the major transmitters in the more northerly areas. The IAH and the Met Office have been investigating whether bluetongue virus could be introduced to the UK by wind blown vector insects. This assessment, carried out in July and August, showed that the risk was medium to low. That risk will rise if the outbreaks in Europe extend further towards the coast and if the winds are from the east.

It is unlikely that adult midges will survive the winter but if the bluetongue virus manages to survive in a vector or a host then new outbreaks can be expected between May and September next year.