While a mosquito bite is usually a minor nuisance, it can be serious in many places. The Aedes aegypti mosquito spreads diseases like dengue, yellow fever, and Zika, while Anopheles gambiae spreads malaria.
The World Health Organization estimates malaria causes over 400,000 deaths each year. Mosquitoes are considered the deadliest animals because of their disease transmission. Only female mosquitoes bite for blood to develop eggs, and scientists have found they use multiple senses to locate their hosts, not just one cue.
Researchers at UC Santa Barbara have found 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 reveals where and how mosquitoes detect infrared. Nicolas DeBeaubien, a co-lead author, explained that this discovery improves understanding of how mosquitoes locate humans.
Mosquitoes like Aedes aegypti use various cues to find hosts, including CO2, odors, vision, body heat, and humidity. However, these cues have limitations. For instance, mosquitoes have poor vision, and strong winds or quick movements can disrupt their sense of chemicals.
Researchers wondered if mosquitoes could detect infrared radiation, a more reliable heat signal. Infrared can travel long distances and heat objects, similar to how pit vipers sense thermal IR.
Researchers tested female mosquitoes in a cage with human odors and CO2. One zone had additional infrared radiation (IR) at skin temperature.
Mosquitoes were more active in searching for a vein in the zone with IR, showing that infrared helps them find hosts. IR remains effective up to about 70 cm away. The study suggests IR is a key sense for mosquitoes, but it works best with other cues like CO2 and human odor.
Mosquitoes can’t detect infrared (IR) radiation like visible light because IR has lower energy and doesn’t activate the same proteins. Instead, they sense IR indirectly. IR from body heat warms specific neurons in their antennae.
Researchers found that these neurons, which have a temperature-sensitive protein called TRPA1, help mosquitoes detect IR. Removing the tips of the antennae or the TRPA1 protein makes mosquitoes unable to sense IR.
The TRPA1 protein helps mosquitoes detect infrared (IR) radiation. However, it might not fully explain their ability to sense IR from up to 70 cm away. Researchers found that TRPA1 alone might not be enough at this distance.
They discovered that certain rhodopsin proteins, which can sense temperature changes, also help with IR detection. While TRPA1 directly responds to stronger IR signals, rhodopsins (Op1 and Op2) can detect weaker signals and boost the mosquito’s IR sensing range to about 2.5 feet.
DeBeaubien and Chandel et al.
Half the world is at risk from mosquito-borne diseases, with about a billion infections yearly. Climate change and travel have spread Aedes aegypti mosquitoes beyond tropical areas, reaching new regions, including parts of the US.
This new research could improve mosquito control methods by using thermal IR in traps. It also explains why loose-fitting clothing is effective against bites. The findings enhance our understanding of how mosquitoes locate humans and offer new ways to manage disease spread.
Journal reference :
- Chandel, A., DeBeaubien, N.A., Ganguly, A. et al. Thermal infrared directs host-seeking behaviour in Aedes aegypti mosquitoes. Nature. DOI: 10.1038/s41586-024-07848-5.
