Rickard Ignell, of the Swedish University of Agricultural Science, had a simple question: Which animals attract mosquitoes and which repel them?
His hope was that the answer might help humans repel mosquitoes and avoid the myriad of diseases—from malaria to Zika—that mosquitoes carry with them.
With the help of his team, he collected Anopheles arabiensis, which is known to carry malaria in sub-Saharan Africa. When they analyzed the blood these mosquitoes had extracted from their victims, they found it belonged to all kinds of farm animals. There was, however, one exception: no chicken blood.
Of 1,172 mosquitoes trapped, only one mosquito seemed to have bit a chicken.
The obvious next step was to test whether this was true. So in an Ethiopian town, some 6,700 people volunteered to sleep with mosquito traps in all bedrooms—but in some they also placed a caged chicken and in others they placed different breeds of farm animal.
When they analyzed the number of mosquitoes caught by each trap, they found that the people who slept with chickens in their bedrooms had fewer of them. The reduction was as high as 80% compared to those with other animals.
It was clear that something about the chickens made them less attractive to mosquitoes. Was it their odor? asked Ignell. So he extracted chemicals from fur and feathers of farm animals. Then, thousands of volunteers slept with odor-emitting devices and mosquito traps. The people who had goat, sheep, or cattle odor in their bedrooms found about the same number of mosquitoes in their traps. However, those who slept with pure chicken odor had 95% fewer mosquitoes. The results were published in Malaria Journal.
The results are exciting for development of more effective repellants. However, Ignell will have to test whether other species of mosquitoes also respond to chicken odor in the same way.
If they do, he would have found an incredibly effective, all-natural mosquito repellant that had been hiding in farms all along.