Arbovirology - continued

When northern European countries experienced their first bluetongue outbreak, in the summer of 2006, we first used a polymerase chain reaction (PCR) test based on the gene encoding virus protein 7, able to detect any and all of the 24 serotypes of BTV, to confirm the presence of the virus. Subsequently we used our VP2-based PCR to demonstrate that the virus was serotype 8 ? which had never previously been identified in Europe.

We then sequenced the whole of the VP2 gene and compared it with other VP2 gene sequences of BTV-8 viruses that had been previously isolated in Africa. This indicated that the BTV-8 virus of northern Europe had originated in sub-Saharan Africa, being most similar to BTV-8 in Nigeria.

The distance from this region to northern Europe is too great for the BTV-8 to have been spread by winds bearing infected midges. How the virus got to northern Europe remains a mystery. In September 2007 samples from British animals suspected as having bluetongue were tested at Pirbright using the PCR tests described above, plus tests for antibody to the virus. These tests confirmed that BTV-8 had been spread to Britain.