As It Happens

How chickens could be on the frontline of the battle against malaria

Scientist Sharon Hill tells us how the smell of a chicken can be used as an incredibly effective repellent for warding off malaria-carrying mosquitoes.
Researchers put caged chickens in the bedrooms of Ethiopian villages to test their theory that certain types of mosquitoes don't like the smell of chickens. (Sharon Hill)
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When people talk about something "passing the smell test," it's usually not literal. But in this case, it is — and it could be a big deal. 

According to a new study, scientists have just discovered that the distinct smell of a chicken — a living, pecking chicken — is incredibly effective at warding off a species of malaria-carrying mosquitoes. 
Sharon Hill is an Associate Professor of Chemical Ecology at the Swedish University of Agricultural Sciences. (Sharon Hill)

"We were definitely surprised," Sharon Hill, a researcher and Associate Professor of Chemical Ecology at the Swedish University of Agricultural Sciences, tells As It Happens guest host Helen Mann.

Hill's group went into villages in Ethiopia, where malaria-carrying mosquitoes are common and becoming increasingly adaptive to repellents. After analysing the insects' blood they found that for some reason they seemed to avoid biting chickens.

"We had done a census of all the animals and there was one chicken blood meal in thousands of samples," Hill explains.

Hill thinks mosquitoes avoiding chickens is a survival instinct. "It's a dangerous place for a mosquito to be because chickens could eat mosquitoes, which isn't the case when it comes to other animals, including humans."

Malaria is caused by Plasmodium parasites, which are carried by mosquitoes and spread through their blood-sucking bites. (CDC/University of Notre Dame/James Gathany/AP)

To test their theory, Hill and her team hung caged chickens at the foot of the villagers' beds while they slept under a mosquito net. Next to the chicken cage was a light trap. In another room, they had the same set up with no chickens. Hill says the results confirmed their hypothesis. 

"There were very few mosquitoes caught when a chicken was present and lots of mosquitoes when it was not present," Hill explains.

A mother and her child sit on Oct. 30, 2009 on a bed covered with a mosquito net near Bagamoyo, 70 kilometres north of Tanzanian capital Dar es Salaam. (TONY KARUMBA/AFP/Getty Images)

Hill's group is now trying to determine exactly which chicken smell is keeping the mosquitoes away. Her group went back to the villages with individual scents from chickens to try to figure out which compounds make the most potent cocktail of scents to repel the mosquitoes.

Hill cautions that the chicken based method is only proven to be effective on a malaria-carrying species of mosquito. The mosquitoes that carry other types of diseases, like Zika, feed on chickens.

But with close to 5 million malaria cases and 70,000 related deaths a year in Ethiopia, Hill hopes her research will aid in the fight against infection. Furthermore, adapting the study to find other non-hosts like chickens could help protect against other mosquito-borne diseases.

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