Midges ‘actively’ spread bluetongue

The midges that spread bluetongue across Europe in 2006 actively carried the disease through flight and were not just swept along by the wind, according to scientists.

The research, by Oxford University, is significant as it could have implications for how other diseases believed to be spread by midges – including the Schmallenberg virus – are tackled by the authorities.

It had been thought that the midges were “passengers” carrying the disease wherever the wind blew them

But a team led by Oxford University scientists, analysing the 2006 outbreak, has shown that active movements of the midges were responsible for around 40% of the spread of the epidemic.

A report of the research appears in this month’s Proceedings of the Royal Society B.

“For the first time we can say that midges, under their own power, travel upwind as well as downwind during this kind of epidemic,” said Dr Luigi Sedda of Oxford University’s Department of Zoology.

“This has very important implications for the control of future epidemics as previously efforts had been targeted at preventing downwind infection.”

The analysis was restricted to Northern Europe (France, Belgium, Netherlands, Germany, and Luxembourg).

Nearly 40% of the midge’s movements during the outbreak were attributed to their own activity with downwind and random movements, or combinations of upwind, downwind and random movements, accounting for the remainder of the infections.

Dr Sedda said: ‘Our model can explain 94% of the over 2,000 farm outbreaks of bluetongue in Northern Europe in 2006. Whilst some infected farms were the source of infections for up to 15 other farms, 70% of all the infected farms were transmission ‘dead ends’ – that is they did not infect other farms.

“These sorts of statistics could help to inform future control policies for bluetongue and other diseases that are spread in a similar way.”

Read more on the Schmallenberg virus on our dedicated page