An international team of scientists including both European institutes and an institute in South Africa has identified the strain of bluetongue that threatened European livestock in 2006-2007. The strain is believed to have originated in sub-Saharan Africa.

The research, which was partly funded by the EU, is published in a recent article in the journal Virology. Barbara Sherry, one of the editors of Virology commented on the importance of such research. 'Such timely and increasingly important insights into the origins of emerging viruses will lead not only to an increased understanding of how viruses like bluetongue virus spread, but also to rational vaccine development,' she commented.

The bluetongue virus is named after its most prominent characteristic; the tongue of afflicted animal turns blue - a condition called cyanosis of the tongue. The virus is also characterised by high fever, excessive salivation and swelling of the head and neck. It is transmitted through insects and attacks ruminant animals such as cattle, goats and deer, but most prominently sheep.

In 2006, authorities were alerted to an outbreak of the bluetongue virus that was spreading across northern Europe. In 2007 the virus came out of hibernation and struck the UK, confirming fears that animal diseases were increasingly crossing international borders.

What also concerned experts was how far north the virus had managed to spread. Initially discovered in South Africa, the bluetongue virus arrived in southern Europe in the late 1990s. It was not expected to migrate further north as experts believed that the virus would not be able to survive the cold temperatures of the European countries located in high latitudes. Cold temperatures and hard frosts effectively kill the midges that transmit the disease.

As the virus had reached as far north as the Netherlands, an explanation was needed as to what was happening. Scientists needed to find out if this was a new viral strain they were dealing with and discover how the virus was adapting.

Their results indicate that despite the high levels of similarity to other European strains, the bluetongue virus affecting European livestock 'represents the introduction of a new strain, originating from sub-Saharan Africa'.

As a result of their research, scientists will be able to compare this strain with any future outbreaks, thereby helping to track the movement of the virus. Any comparisons made will also help to identify any subsequent re-assortment events involving this strain and assist in identifying other related strains occurring in different locations.

Its arrival so far north has been attributed to climate change, and the initial outbreak coincided with record high temperatures recorded across Europe in 2006. However, instead of being destroyed by the cold winter, the virus successfully overwintered and continued its progress across Europe in 2007. In some areas of Europe close to 50% of livestock were lost due to bluetongue virus.

EU control measures for bluetongue

Source: Community R&D Information Service (CORDIS)