Compounds in chicken feathers repel malarial mosquitoes in Africa.
Chickens vs. malaria. I’m Bob Hirshon and this is Science Update.
Malaria remains one of the most deadly diseases on the planet today. But it may have a formidible enemy: the chicken. Researchers report in Malaria Journal that the birds are a big turn off for Anopheles arabiensis, a malarial mosquito that’s gaining ground in Africa. Swedish University of Agricultural Science’s Rickard Ignell and his colleagues studied its feeding patterns.
The malaria mosquitoes were feeding on humans when we found them indoors but cattle when we found them outdoors, but never chicken.
Ignell says the insects likely view the birds as a threat. He and his colleagues identified four odor compounds in chicken feathers that successfully repelled mosquitoes away from sleeping volunteers. When used in combination with other methods, the compounds could be an effective way to deter mosquitoes from large areas. I’m Bob Hirshon, for AAAS, the science society.
Making Sense of the Research
Could it be that the odor of chickens could prove to be a serious deterrent to malaria-carrying mosquitoes? According to this research, it looks like this may be a distinct possibility.
Dr. Ignell and his colleagues carried out their research in three villages in western Ethiopia where people often share their living quarters with their livestock. Malaria, a mosquito-borne disease caused by a parasite that can produce fever, chills, and flu-like symptoms, is still a major health issue in Ethiopia, which has about 5 million cases and 70,000 deaths a year. Globally, there were 214 million cases of malaria in 2015 and 438,000 deaths because of it, according to the World Health Organization. It is the fourth-leading cause of death in sub-Saharan Africa among children under five.
They focused their research on the malaria-carrying mosquito Anopheles arabiensis. They collected 1,172 of these mosquitoes that strongly prefer human over the livestock blood. Among livestock, however, they would bite cattle, sheep, and goats. Only one of the mosquitoes they collected had bitten a chicken. In fact, it appears that this species of mosquitoes avoids birds in general.
Since this species of mosquito uses its sense of smell to find food, the researchers decided to carry out their study by collecting hair, wool, and feather samples from the livestock in the villages. They then identified the odorants (substances that give off a smell) unique to each sample. The team then isolated four compounds specific to chickens, so they could generate pure chicken odor.
In order to test how well or if this odor would repell mosquitoes, the researchers solicited thousands of volunteers from the Ethiopian villages to act as mosquito bait. These volunteers stayed in bedrooms filled with devices that emitted the odors of cattle, sheep, goats, or chickens. The results of the research showed about a 90 to 95 percent reduction in mosquito counts for those bedrooms that had the chicken odor. In fact, using a live chicken suspended in a cage in the room also successfully repelled the mosquitoes—with about an 80 percent reduction in mosquito counts.
The researchers aren't sure why these mosquitoes avoid chickens. They speculate that it could be because chicken blood might be poor in nutrients or is difficult for the insects to digest. Another possibility is that birds pose a threat to mosquitoes, and so the insects have evolved to avoid them.
Dr. Ignell and his colleagues are hopeful, though, that these findings could lead to new, all-natural mosquito repellents that can, in combination with tools such as bed nets, help protect people from malaria.
Now try and answer these questions:
- What is malaria?
- Where did Dr. Ignell and his colleagues conduct their research?
- What type of mosquito did they study?
- How did they figure out that the mosquitoes avoided biting chickens?
- How did the scientists carry out their research?
- Do you have some ideas about why the mosquitoes would avoid biting chickens? How would you go about testing your idea?
To learn about another disease that is carried by mosquitoes, you can listen to West Nile Weather, which looks at how scientists try to predict how severe an outbreak of the virus may be in a particular year.
You can supplement what your students learned about malaria with this Science Update by watching Malaria: blood, sweat, and tears. In this video, photojournalist Adam Nadel offers insights into his exhibition, which was featured in the AAAS Gallery in 2012. This video can be used to help students explore the human cost of the disease and how people are trying to combat it.
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