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BTV-8 re-emerging in northern Europe, APHA warns


Owing to the weaker pathogenicity of the re-emerging strain, there may be fewer clinical signs than the 2007 strain.

Weaker pathogenicity means clinical signs may be fewer  

Vets are being reminded of the risk of bluetongue virus, as serotype 8 re-emerges in northern Europe. 

According to an APHA briefing, there have been reports from France of calves being born small and blind, dying at just a few days old, since mid-December 2018. There has been a considerable increase in reports since January this year.

The affected animals have been positive by PCR on blood and spleen for BTV-8. APHA said the detection of BTV-8 in calves of around a week old, during the culicoides vector-free period, suggests transplacental infection.

Since the first reports of cases, 418 samples have tested positive for BTV-8 by PCR, with between two and 15 per cent of newborn calves affected on some farms.

Further studies using experimental midge infection suggest that the current BTV-8 strain in France has a reduced culicoides vector competence.

Official veterinarians are being urged to consider BTV-8 as a possible cause of malformed calves or abortion, and to be aware that the re-emerging strain in northern Europe could cause transplacental transmission and infection of foetuses in cattle.

Owing to the weaker pathogenicity of the re-emerging strain, there may be fewer clinical signs than the 2007 strain, so APHA says an increase in awareness is important.