While a mosquito bite is usually only a minor inconvenience, in many places it can have serious consequences. The Aedes aegypti mosquito spreads diseases such as dengue fever, yellow fever and Zika, while the Anopheles gambiae spreads malaria.
The World Health Organization estimates that malaria kills over 400,000 people each year. Mosquitoes are considered the deadliest animals because they transmit diseases. Only female mosquitoes bite to get blood and develop eggs. Scientists have found that they use multiple senses to locate their hosts, rather than just a single cue.
Researchers at UC Santa Barbara have discovered that mosquitoes can detect infrared radiation, which helps them find hosts. When combined with CO2 and human odor, infrared radiation doubled their host-seeking behavior.
The study in Nature shows where and how mosquitoes sense infrared. Nicolas DeBeaubien, one of the lead authors, said that this discovery improves the understanding of how mosquitoes locate people.
Mosquitoes like Aedes aegypti use a variety of signals to find hosts, including CO2, smells, vision, body heat and moisture. However, these signals have limitations. For example, mosquitoes have poor eyesight and strong wind or rapid movement can impair their sense of chemicals.
Researchers wondered if mosquitoes could sense infrared radiation, a more reliable heat signal. Infrared can travel long distances and heat objects, similar to how pit vipers sense thermal infrared radiation.
The researchers tested female mosquitoes in a cage with human odors and CO2. One zone also had infrared radiation (IR) at skin temperature.
Mosquitoes searched more actively for a vein in the zone with infrared, showing that infrared helps them find hosts. Infrared remains effective up to a distance of about 70 cm. The study suggests that infrared is an important sense for mosquitoes, but works best with other stimuli such as CO2 and human odor.
Mosquitoes cannot sense infrared radiation (IR) like they can see visible light because IR has less energy and does not activate the same proteins. Instead, they sense IR indirectly. IR from body heat heats up certain neurons in their antennae.
Researchers found that these neurons, which have a temperature-sensitive protein called TRPA1, help mosquitoes detect IR. By removing the antenna tips or the TRPA1 protein, mosquitoes can no longer detect IR.
The protein TRPA1 helps mosquitoes detect infrared radiation (IR). However, it does not fully explain their ability to detect IR from up to 70 cm away. Researchers found that TRPA1 alone may not be sufficient at this distance.
They discovered that certain rhodopsin proteins that can sense temperature changes also help with IR detection. While TRPA1 responds directly to stronger IR signals, rhodopsins (Op1 and Op2) can detect weaker signals, increasing the mosquito’s IR detection range to about 75 cm.
Half of the world’s population is at risk from mosquito-borne diseases. About a billion people fall ill with these diseases each year. Due to climate change and increased travel, Aedes aegypti mosquitoes have spread beyond the tropics into new regions, including parts of the United States.
This new research could improve mosquito control through the use of infrared thermal traps. It also explains why loose-fitting clothing is effective against bites. The findings expand our understanding of how mosquitoes track down people and offer new opportunities to control the spread of disease.
Journal reference:
- Chandel, A., DeBeaubien, NA, Ganguly, A. et al. Thermal infrared controls host-seeking behavior in Aedes aegypti mosquitoes. Nature. DOI: 10.1038/s41586-024-07848-5.
