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working on an experiment
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Credit: Carrie Rosema
House-dwelling, malaria-carrying mosquitoes can detect minute changes in concentrations of exhaled carbon dioxide to determine when humans are present, according to research published in the Journal of Chemical Ecology.
Anopheles gambiae mosquitoes spend much of their adult lives indoors, where they are constantly exposed to human odor, even when people are absent.
But researchers found these mosquitoes respond very weakly to human skin odor alone.
Experiments showed that mosquitoes were more likely to a land on a source of skin odor if carbon dioxide was also present, even at very low levels.
“Responding strongly to human skin odor alone once inside a dwelling where human odor is ubiquitous is a highly inefficient means for the mosquito of locating a feeding site,” said study author Ring Cardé, PhD, of the University of California, Riverside.
“We already know that mosquitoes will readily fly upwind towards human skin odor, but landing, the final stage of host location, which typically takes place indoors, does not occur unless a fluctuating concentration of carbon dioxide indicates that a human host is present.”
Dr Cardé and his colleagues discovered the importance of carbon dioxide in mosquitoes’ landing patterns by studying Anopheles gambiae mosquitoes collected in Cameroon.
The researchers collected skin odor by using pieces of white polyester gauze worn by one of the study authors in a cotton sock for 4 to 6 hours before the experiments began. The team then recorded the mosquitoes’ landing behavior with a video camera equipped with night vision.
The landing behavior “dramatically increased” with the addition of carbon dioxide at a range of concentrations above ambient. This was true even when the carbon dioxide level was just 0.015% above ambient within the assay cage.
These results suggest the mosquitoes use a “sit-and-wait” ambush strategy during which they ignore persistent human odor until a living human is present.
One take-home message from this work is that researchers investigating which human odors mediate host-finding and which compounds are good mosquito repellents need to precisely control exposure to carbon dioxide. A researcher entering an assay room quickly elevates the level of carbon dioxide, thereby altering the mosquitoes’ behavior.
“It also would be useful next to see if mosquitoes’ response to skin odor is similarly affected by carbon dioxide in outdoor situations and how these interactions play out in human dwellings,” Dr Cardé noted. 
working on an experiment
involving a wind tunnel
Credit: Carrie Rosema
House-dwelling, malaria-carrying mosquitoes can detect minute changes in concentrations of exhaled carbon dioxide to determine when humans are present, according to research published in the Journal of Chemical Ecology.
Anopheles gambiae mosquitoes spend much of their adult lives indoors, where they are constantly exposed to human odor, even when people are absent.
But researchers found these mosquitoes respond very weakly to human skin odor alone.
Experiments showed that mosquitoes were more likely to a land on a source of skin odor if carbon dioxide was also present, even at very low levels.
“Responding strongly to human skin odor alone once inside a dwelling where human odor is ubiquitous is a highly inefficient means for the mosquito of locating a feeding site,” said study author Ring Cardé, PhD, of the University of California, Riverside.
“We already know that mosquitoes will readily fly upwind towards human skin odor, but landing, the final stage of host location, which typically takes place indoors, does not occur unless a fluctuating concentration of carbon dioxide indicates that a human host is present.”
Dr Cardé and his colleagues discovered the importance of carbon dioxide in mosquitoes’ landing patterns by studying Anopheles gambiae mosquitoes collected in Cameroon.
The researchers collected skin odor by using pieces of white polyester gauze worn by one of the study authors in a cotton sock for 4 to 6 hours before the experiments began. The team then recorded the mosquitoes’ landing behavior with a video camera equipped with night vision.
The landing behavior “dramatically increased” with the addition of carbon dioxide at a range of concentrations above ambient. This was true even when the carbon dioxide level was just 0.015% above ambient within the assay cage.
These results suggest the mosquitoes use a “sit-and-wait” ambush strategy during which they ignore persistent human odor until a living human is present.
One take-home message from this work is that researchers investigating which human odors mediate host-finding and which compounds are good mosquito repellents need to precisely control exposure to carbon dioxide. A researcher entering an assay room quickly elevates the level of carbon dioxide, thereby altering the mosquitoes’ behavior.
“It also would be useful next to see if mosquitoes’ response to skin odor is similarly affected by carbon dioxide in outdoor situations and how these interactions play out in human dwellings,” Dr Cardé noted.
working on an experiment
involving a wind tunnel
Credit: Carrie Rosema
House-dwelling, malaria-carrying mosquitoes can detect minute changes in concentrations of exhaled carbon dioxide to determine when humans are present, according to research published in the Journal of Chemical Ecology.
Anopheles gambiae mosquitoes spend much of their adult lives indoors, where they are constantly exposed to human odor, even when people are absent.
But researchers found these mosquitoes respond very weakly to human skin odor alone.
Experiments showed that mosquitoes were more likely to a land on a source of skin odor if carbon dioxide was also present, even at very low levels.
“Responding strongly to human skin odor alone once inside a dwelling where human odor is ubiquitous is a highly inefficient means for the mosquito of locating a feeding site,” said study author Ring Cardé, PhD, of the University of California, Riverside.
“We already know that mosquitoes will readily fly upwind towards human skin odor, but landing, the final stage of host location, which typically takes place indoors, does not occur unless a fluctuating concentration of carbon dioxide indicates that a human host is present.”
Dr Cardé and his colleagues discovered the importance of carbon dioxide in mosquitoes’ landing patterns by studying Anopheles gambiae mosquitoes collected in Cameroon.
The researchers collected skin odor by using pieces of white polyester gauze worn by one of the study authors in a cotton sock for 4 to 6 hours before the experiments began. The team then recorded the mosquitoes’ landing behavior with a video camera equipped with night vision.
The landing behavior “dramatically increased” with the addition of carbon dioxide at a range of concentrations above ambient. This was true even when the carbon dioxide level was just 0.015% above ambient within the assay cage.
These results suggest the mosquitoes use a “sit-and-wait” ambush strategy during which they ignore persistent human odor until a living human is present.
One take-home message from this work is that researchers investigating which human odors mediate host-finding and which compounds are good mosquito repellents need to precisely control exposure to carbon dioxide. A researcher entering an assay room quickly elevates the level of carbon dioxide, thereby altering the mosquitoes’ behavior.
“It also would be useful next to see if mosquitoes’ response to skin odor is similarly affected by carbon dioxide in outdoor situations and how these interactions play out in human dwellings,” Dr Cardé noted.