Light Augments Conventional Methods of Mosquito Control

Exposure to just 10 minutes of white light presented at timed intervals during the late daytime, dusk, dawn and throughout the night could suppress biting and manipulate flight behavior in the Anopheles gambiae mosquito, the major vector for transmission of malaria in Africa. Researchers believe that a photic exposure method could be used to reinforce current insect control techniques or be implemented as a standalone approach.

Critical behaviors exhibited by the Anopheles gambiae are time-of-day specific, including a greater propensity for nighttime biting.

Scientists at the University of Notre Dame have found that exposure to just 10 minutes of light at night suppresses biting and manipulates flight behavior in the Anopheles gambiae mosquito, the major vector for transmission of malaria in Africa. Courtesy of the University of Notre Dame.

To test biting behavior, researchers separated mosquitoes 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 at the onset of night. A human-subject biting assay was conducted, and the proportion of biting was recorded every two hours over an eight-hour period. Results showed that the pulse significantly reduced biting propensity two hours and in some trials four hours following its administration. No differences were detected six hours after the pulse was administered.

Looking for a way to use light to reduce biting throughout the night, researchers exposed mosquitoes to a series of pulses presented every two hours. They noted an immediate suppressive effect of light during the exposure period and two hours after the pulse, although differential responses that were time-of-day specific suggested an underlying circadian property in the mosquito physiology.

Researchers also examined the immediate and sustained effects of light on mosquito flight activity following exposure to a 30-minute pulse. They observed activity suppression during early night and elevated activity during the late 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,” University of Notre Dame professor Giles Duffield said. “This may prove to be an effective tool that complements established control methods used to reduce disease transmission.”

Pulses of light would probably be more effective than constant exposure, Duffield said, as the mosquitoes would be less likely to adapt to light presented in periodic doses. The research team is testing the effectiveness of different wavelengths of light, such as red light, that would be less disturbing to adults and children while they sleep, with an aim toward developing field-applicable solutions.

As the efficacy of established methods of control is further compromised by increasing resistance to insecticides and the insects’ behavioral adjustments, the inhibitory effects of light exposure and the use of multiple photic pulses presented at intervals during the night and late daytime could prove to be an effective tool that complements established control methods.

Malaria infects over 250 million people and kills approximately 438,000 individuals annually. Approximately 90 percent of these deaths occur in Africa, predominantly in children aged five years and under.

The research was published in Parasites & Vectors (doi: 10.1186/s13071-017-2196-3).