4 November 2008

Scientists at the Institute of Virology and Immunoprophylaxis (IVI), the national bluetongue reference laboratory in Switzerland, and the Institute for Animal Health (IAH) Pirbright Laboratory have collaborated on the identification of a new bluetongue virus (BTV), called “Toggenburg Orbivirus” (TOV) from goats in Switzerland.

The Swiss scientists sequenced the genes of TOV, demonstrating that the virus is not serotype 8 (which is widespread in northern Europe and which came to the UK in 2007) and is not serotype 1 (which is spreading northwards through France). Rather, the sequence data indicates that it represents a previously undiscovered 25th serotype. The IVI scientists have just published their findings in the journal Emerging Infectious Diseases*.

 

Blood samples from animals infected with the new virus were sent to IAH for antibody testing, as IAH Pirbright is the Bluetongue Reference Laboratory of the World Organisation for Animal Health (OIE) and the European Union. The results support the conclusion derived from gene sequencing that TOV represents a new serotype of BTV.

 

The new BTV was detected by researchers at the IVI diagnostics laboratory in 2008 in two goat herds over 100 km apart. The virus did not cause distinct clinical signs when inoculated experimentally into goats. The existence of the virus was detected by routine surveillance of animals for export to Sweden

 

Twenty-four serotypes of BTV have been known for some years. If an animal is infected by one serotype of BTV and survives, then it is protected against subsequent infection - but only against the same serotype. On the surface of BTV virus are two proteins (VP2 and VP5). It is antibodies that form against these two proteins (after infection or vaccination) that subsequently protect an animal from a second infection. The Swiss scientists have also sequenced the genes for VP2 and VP5, showing that they are very different from those of the other 24 serotypes. This indicates that TOV is indeed a new BTV serotype.

 

“To discover a new BTV is interesting, but to discover it in central Europe is most surprising,” said Professor Peter Mertens of the IAH. “This new BTV is so different from other ones that we cannot even guess where it came from.” “Although the virus did not cause overt disease in goats, if it started to spread and behave like other BTV strains, then it could become a more serious threat to ruminants, especially as there would be no vaccine against it.”

 

The findings of the Institute of Virology and Immunoprophylaxis are published in the journal Emerging Infectious Diseases:
Hofmann MA, Renzullo S, Mader M, Chaignat V, Worwa G, Thuer B. Genetic characterization of Toggenburg Orbivirus, a new Bluetongue Virus, from Goats, Switzerland. Emerging Infectious Diseases. 2008 December. E-publication available free of charge ahead of the print version: http://www.cdc.gov/ncidod/EID/index.htm