Mosquitoes have long been known to rely on smell, carbon dioxide and body heat to find humans. New research from the University of California, Santa Barbara has now identified another important cue: infrared radiation emitted by human skin.
Infrared detection
Researchers studying Aedes aegypti, a mosquito species that spreads dengue, yellow fever and Zika, found that infrared radiation from a source close to human skin temperature doubled host-seeking behaviour when combined with human odour and carbon dioxide.
Infrared radiation alone did not attract mosquitoes. According to the researchers, it became effective only when presented together with other human cues, such as breath and smell.
How mosquitoes find humans
Female mosquitoes need blood to develop their eggs, while male mosquitoes do not bite. Scientists have spent more than a century studying how females locate their hosts.
Mosquitoes use several signals at different distances, including carbon dioxide from exhaled breath, body odour, vision, humidity and heat from the skin. The new study shows that infrared radiation also helps guide them towards people.
The experiment
The researchers placed female mosquitoes in a controlled environment with two zones. Both zones contained human odour and carbon dioxide at levels similar to human breath, but only one also had infrared radiation from a source at about 34 degrees Celsius, close to skin temperature.
A barrier prevented heat transfer through direct contact or air movement. The team then measured how many mosquitoes began probing, a behaviour linked to searching for a blood vessel.
Why clothing matters
The findings may also explain why loose-fitting clothing helps reduce mosquito bites. Loose clothing blocks direct access to the skin and allows infrared radiation to disperse between the body and the fabric, making humans harder for mosquitoes to detect.
Public health relevance
Mosquito-borne diseases affect large parts of the world. Aedes aegypti spreads viruses including dengue, yellow fever and Zika, while Anopheles gambiae spreads the parasite that causes malaria.
The researchers say the discovery could help improve mosquito control, including traps that use thermal infrared radiation at temperatures similar to human skin.
Source: Earth.com / Nature
