18 July 2017

Africa: Shining Light At Night Quells Mosquito Bites

Photo: UNHCR/F.Noy
(file photo).

Cape Town — Exposing malaria-transmitting mosquitoes to light at two-hour intervals during the night or at late daytime could inhibit their biting behaviour and reduce malaria transmission, says a study.

According to the World Health Organization, 214 million people worldwide were infected with malaria in 2015, resulting in 438,000 deaths, with 88 per cent of the cases and deaths occurring in Africa.

The team behind the research, from the University of Notre Dame in the United States, note that the development of resistance to insecticides requires innovative approaches for controlling the malaria vector.

Therefore, they explored the potential of using light to control mosquitoes' feeding behaviour by exposing Anopheles gambiae mosquitoes - a key vector of malaria in Sub-Saharan Africa - to multiple pulses of bright light, especially in the night, when they are most likely to feed on human blood.

"When we subjected the mosquitoes to a series of pulses of light with a two-hour interval and presented throughout the entire night, we observed suppression of biting activity during most of the night," says Giles Duffield, a co-author of the study published in the journal Parasites & Vectors last month (16 June).

Giles, an associate professor of biological sciences at the University of Notre Dame, tells SciDev.Net that the finding was most prominent during the early to middle of the night and at dawn, when people are least protected by the barrier of a bed net.

"Conversely, biting levels were significantly elevated when mosquitoes were exposed to a dark treatment during the late day, suggesting that light suppresses biting behaviour even during the late daytime," the researchers note in the paper.

This is an interesting study, says Maureen Coetzee, director at the Wits Research Institute for Malaria, Witwatersrand University, South Africa.

But Coetzee notes that most Africans live in rural areas with no electricity. This means a lighting system would have to be set up using batteries or a generator, making the practical implementation of the method a big challenge.

"I wonder how many people would be able to afford to set this up themselves, and I can't see governments providing such equipment," she tells SciDev.Net.

Coetzee says to get protection throughout the night, the light would need to be switched on every two hours, which would disrupt human sleeping patterns as well as mosquito biting behaviour.

"If I was woken up every two hours with the light going on for ten minutes, it would not take long before I started to suffer from sleep deprivation and I would switch the device off," she says.

Giles agrees with the authors that more experimental work needs to be conducted, both in the laboratory where the environmental conditions can be carefully controlled, as well as under field conditions that match a more natural setting.

This piece was produced by SciDev.Net's Sub-Saharan Africa English desk.


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