“Bar-coding” midges could help prevent spread of bluetongue in the UK

Bluetongue is a serious disease affecting ruminants such as sheep and cattle. It was first detected in the UK in 2007 but has not yet affected Scotland. It can be spread by species of Culicoides biting midge present in the UK. European midges have been exposed to bluetongue and can spread the disease. Coupled with climate change, this means the disease poses a major threat to UK agriculture.

The species of midges present in the UK potentially differ in their ability to spread bluetongue, so predicting how the disease might spread depends on mapping the distribution of these species. DeGabriel’s new “bar-coding” system makes this possible for the first time.

According to DeGabriel: “The four species within the group Culicoides obsoletus that we are interested in cannot be distinguished visually. So we are using a genetic bar-coding approach to identify the midges to species level using molecular methods. We have developed a high-throughput genetic screening method to identify large sample sizes of midges to species level, both efficiently and cost-effectively.”

During 2007 and 2008, DeGabriel and her colleagues collected one million midges from light traps set up on 37 farms throughout Scotland, from the English border in the south to as far north as Thurso. Using the bar-coding technique they were then able to produce a detailed “midge map” of Scotland. This showed midge numbers and species varied both geographically and seasonally, reflecting differences in climate and habitat.

“This is the first large-scale study of the distribution and abundance of Scottish midge species. We found that all four species of midges were present in all areas of Scotland, but the relative numbers of each species differed between the trapping sites. We also found the mixture of species differed at individual sites at different times of the year. These differences between and within sites appear to be due to differences in climatic conditions and habitat. Our findings provide vital information for assessing the risk of bluetongue being transmitted in Scotland and the effects of climate change on the spread of this and other animal diseases,” DeGabriel explains.

“Given the introduction of bluetongue into England and the persistence of favourable climatic conditions such as the recent milder winters, this research is extremely urgent and important. Our results will help scientists and policy makers develop risk mitigation and management strategies for bluetongue and other animal diseases,” DeGabriel says.

Jane DeGabriel will present her full findings at 09:10 on Thursday 4 September 2008 to the British Ecological Society’s Annual Meeting at Imperial College, London.

Her research is being carried out under a Scottish Government grant to the University of Aberdeen, Advanced Pest Solutions Ltd and the Institute for Animal Health, Pirbright.