Why Do Some People Get Bitten By Mosquitoes More Than Others?

James Logan, a research student at the BBSRC-sponsored institute Rothamsted Research in Hertfordshire, has found that some people give off "masking" odours that prevent mosquitoes from finding them. His research builds on earlier studies on cattle at Rothamsted Research, led by Professor John Pickett, which showed that the number of flies on a herd depended on certain cows being present. The scientists found these key unattractive individuals gave out different chemical signals from the other cows. When these individuals were moved to another field the number of flies afflicting the herd increased.

James, working in collaboration with Professor Jenny Mordue at the University of Aberdeen, tested the behavioural reaction of yellow fever mosquitoes to the odour of the volunteers. James said: "The mosquitoes were placed into a y-shaped tube and given the choice of moving upwind down either branch. The air flowing down one branch was laced with odour from the volunteer's hands."

Their results suggest that differential attractiveness is due to compounds in unattractive individuals that switch off attraction either by acting as repellents or by masking the attractant components of human odour. This theory differs from that of other research groups who have suggested that unattractive individuals lack the attractive components. The researchers are now testing these theories further using foil sleeping bags to collect whole body odours from volunteers.

Professor Julia Goodfellow, BBSRC Chief Executive, said, "There are clear benefits from this research. Discovering what makes a person more attractive to mosquitoes presents scientists with the opportunity to develop safe, naturally occurring insect repellent which could be far more effective than conventional products because it relates to the way mosquitoes select their hosts." James said, "By identifying these key components and understanding how they work we could be closer to new methods of protection from these biting pests that cause losses in livestock and irritation and illness in humans."

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Notes:

This research features in the January 2005 issue of Business, the quarterly magazine of the Biotechnology and Biological Sciences Research Council.

The original work on Holstein-Frisian heifers was carried out at Rothamsted Research in collaboration with the Danish Institute of Agricultural Sciences and funded by the European Union.

The compounds that attracted the mosquitoes were identified using the coupled GC-EAG method. High-resolution gas chromatography is use to split odour extracts into their components parts. These are then passed over the antenna of an insect. Micro-electrodes attached to the antenna detect electrophysiological responses, which indicate that the insect is sensing the compound. Mass spectrometers are then used to identify the compound.

About BBSRC

The Biotechnology and Biological Sciences Research Council (BBSRC) is the UK funding agency for research in the life sciences. Sponsored by Government, BBSRC annually invests around £300 million in a wide range of research that makes a significant contribution to the quality of life for UK citizens and supports a number of important industrial stakeholders including the agriculture, food, chemical, healthcare and pharmaceutical sectors. http://www.bbsrc.ac.uk