Belgian scientists have confirmed that the Schmallenberg virus is transmitted by three particular species of biting midge that are also known to transmit bluetongue – all of which are common to Great Britain.

Belgian scientists have confirmed that the Schmallenberg virus is transmitted from animal to animal by three species of biting midge that are also known to transmit bluetongue – all of which are common to Great Britain.

Midges are really small. There is a reason why they are popularly called no-see-ums. Here one is compared to a common mosquito. © ITGThe tiny insects were proven as the culprits in a joint effort by researchers from the Antwerp institute of Tropical Medicine (ITG) and the Belgian Veterinary and Agrochemical Research Centre (VAR).

Although, originally, it was unknown how the virus was transmitted, midge-borne diseases such as Shamonda and the bluetongue virus in ruminants meant midges were the “logical suspects”.

With this in mind ITG scientists, who monitor the distribution of midges as vectors of bluetongue for the Belgian authorities, revisited its collection of midges to discover whether it also contained the Schmallenberg virus (SBV).

Using a specially developed ‘microarray’ (a molecular technology that can be used by non-specialists to simply and accurately recognise midge species) ITG scientists collaborated with colleagues at VAR, who had the molecular analytic technology to detect the virus, and discovered SBV in midges caught in September and October 2011.

The virus was found in Culicoides obsoletus, C. dewulfi and C. pulicaris, three of the five species that have been shown to transmit bluetongue, all of which are common to Great Britain.

Culicoides obsoletus, particularly, is said to be widespread on UK farms.

DEFRA and the AHVLA now claim they “cannot rule out the possibility that domestic (local) midges may have transmitted SBV within the affected areas” as domestic midges may have become infected after biting a local animal infected during the incursion of continental midges last summer.

 

  • Both Belgian teams are now working their way through the rest of the ITG’s midge archive with the intention of publishing their findings in a scientific journal.
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