Exposing malaria-spreading mosquitoes to just 10 minutes of light at night may suppress biting and manipulate their flight behaviour, scientists say. Critical behaviours exhibited by the Anopheles gambiae mosquito - the major vector for transmission of malaria in Africa - such as feeding, egg laying and flying, are time-of- day specific, including a greater propensity for nighttime biting. Insecticide-treated bed nets and walls have helped prevent bites and reduce malaria, but researchers say mosquitoes are adapting to preventive conditions, leaving adults and children vulnerable in the early evening and early morning hours - when they are not under the nets or in the house. "Anopheline mosquitoes are adapting to current preventive methods by developing resistance to insecticides and by shifting feeding to earlier in the evening or later into the early morning, times of the day when people are not in bed and therefore not protected by a net," said Giles Duffield, associate professor at the University of Notre Dame in the US. Researchers tested the mosquitoes' preference to bite during their active host-seeking period by separating them into multiple control and test batches. Control mosquitoes were kept in the dark, while test batches were exposed to a pulse of white light for 10 minutes. Researchers then tested the propensity of the mosquitoes to bite immediately after the pulse and every two hours throughout the night, holding their arms to a mesh lining that allowed uninfected mosquitoes to feed while remaining contained. Results indicated a significant suppression.
In another experiment, mosquitoes were pulsed with light every two hours, and using this multiple pulse approach the team found that biting could be suppressed during a large portion of the 12- hour night. "Most remarkable is the prolonged effect a short light treatment has on their preference to bite, with suppression lasting as long as four hours after the pulse," Duffield said. "This may prove to be an effective tool that complements established control methods used to reduce disease transmission," he added. Pulses of light would probably be more effective than constant exposure as the mosquitoes would be less likely to adapt to light presented in periodic doses, researchers said. The study was published in the journal Parasites and Vectors.
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