Flight patterns reveal how mosquitoes find hosts to transmit deadly diseases

Sep 30, 2011
An Aedes aegypti mosquito prepares to bite a human. Credit: Image courtesy of USDA.

The carbon dioxide we exhale and the odors our skins emanate serve as crucial cues to female mosquitoes on the hunt for human hosts to bite and spread diseases such as malaria, dengue and yellow fever.

Two at the University of California, Riverside have now performed experiments to study how female Aedes aegypti -- mosquitoes that transmit and -- respond to plumes of and human odor.

The researchers report in the October 15 issue of the Journal of Experimental Biology that puffs of exhaled carbon dioxide first attract these mosquitoes, which then proceed to follow a broad skin odor plume, eventually landing on a .

The results from the study by Ring Cardé, a distinguished professor of entomology at the University of California, Riverside, and Teun Dekker, formerly a graduate student in Cardé's lab and now an assistant professor at the Swedish University of Agricultural Research, could clue scientists on how odors can be used in traps for intercepting and capturing host-seeking mosquitoes.

Yellow fever is a viral disease that causes 30,000 deaths worldwide each year. Dengue, another viral disease, infects 50 to 100 million people worldwide a year, leading to half a million hospitalizations, and 12,500,000 deaths.

In the lab, the researchers released female yellow fever mosquitoes into a wind tunnel they built, and filmed their flight paths. They found that:

  • Mosquitoes head upwind only briefly when they encounter just a whiff of carbon dioxide but proceed continuously upwind when the carbon dioxide plume is turbulent, fluctuating in concentration and mimicking the presence of a live host.
  • Mosquitoes' orientation to human skin odor, in contrast, is optimal when the plume of skin odor is broad and unvarying in its intensity, as would occur when a mosquito closes in on a potential host.
"Carbon dioxide induces a faster and more direct upwind orientation than skin odor," said Cardé, who holds the Alfred M. Boyce Chair in Entomology. "Our experiments show that the response of yellow fever mosquitoes to skin odor requires an exposure longer than that of carbon dioxide to induce upwind flight."

Dekker and Cardé also report that the dynamics -- response time, duration and speed -- of carbon dioxide-induced upwind surging were very similar across a wide range of carbon dioxide concentrations, from 100 to 0.05 percent (barely above atmospheric levels).

"The mosquitoes' carbon dioxide receptors allow the insects to respond almost instantly to even the slightest amount of the gas," Cardé said. "Carbon dioxide alone attracts these and does not require assistance from other odors. Skin odors, however, become important when the mosquito is near the host, selecting biting sites. Further, the mosquitoes' sensitivity to skin odors increases 5- to 25-fold after 'priming' with a whiff of carbon dioxide."

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User comments : 5

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hush1
not rated yet Oct 01, 2011
See solution:
http://www.physor...ars.html

Last comment. Your welcome.
hush1
not rated yet Oct 01, 2011
Are the wings regenerative - regrowth after damage?
Without the genetics -
Simply trim one side and observe flight pattern results.
Skepticus
not rated yet Oct 01, 2011
if you can't spare 20 bucks for a mosquito net due to laziness or cultural reasons, you are welcome to spend 100s on medicines and help the pharmacoms' shareholders' dividents.
DavidMcC
not rated yet Oct 03, 2011
Hush1, I see no difference between your "solution" and the usual practice of creating large numbers of genetically sterile males. Both suffer from the disadvantage that the modified genotype is strongly selected against.

OK, sterilization isn't usually carried out by anything as complicated as genetic modification, but the effect is the same. The process has to be repeated again and again.
hush1
not rated yet Oct 08, 2011
DavidMcC, I don't see your point. What selects strongly against altered flight dynamics? You have mosquitoes flying in circles - the radius determined by the difference of the right wingspan against the left wingspan.

If the genetic modification runs amok - spreading to all species you have all mosquitoes flying in circles.

If wind drift moves the entire circling mosquitoes to populated areas you still have circling mosquitoes.

You lost me. Why must the process be repeated again and again.
What is selecting against circling mosquitoes?

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