Bluetongue affects livestock including sheep (which are most severely affected), cattle and goats along with wild animals such as deer.

The bluetongue virus (BTV) that causes the disease is mainly spread by Culicoides biting midges. Controlling bluetongue is a challenge as Culicoides midges are tiny and are easily carried on the wind.

The use of ovalbumin, a protein in egg white, to mark insects has previously been used to track and study crop pests. The technique is sensitive enough to show if even a single insect has been exposed and enables them to be marked without the need for collection.

Dr Chris Sanders, a senior post-doctoral entomologist at Pirbright and lead author of a new study, published in the Journal of Applied Ecology explored whether the approach could also be used to track Culicoides midges. The research is the first to measure how many midges might travel between farms, and could help countries that are threatened by BTV to respond more rapidly in an outbreak to control the spread of the virus.

Dr Sanders said: “By combining this data with information from on-site weather stations, we found that the Culicoides midges had flown upwind and downwind towards the traps, and we think that a significant number are actively moving between farms.

“Midges are too small to track by eye or with cameras or radar technology. People have tried capture-mark-recapture, but this is very hard work for small insects because so few marked insects are usually recovered. This research means we now have a much better understanding of the movement of the Culicoides midge species that transmits BTV and have the data we need to estimate the likely spread of the disease between farms more accurately.”