Targeted: Female mosquitoes transmit the malaria parasite. Picture: ISTOCK
Targeted: Female mosquitoes transmit the malaria parasite. Picture: ISTOCK

Sometime in the future, SA’s fight against malaria might involve the unusual sight of a fleet of drones carrying swarms of male mosquitoes. Sterile due to a blast of sperm-damaging radiation that has no effect on humans or the environment, they will be released above a malaria hotspot.

These mosquitoes could also be sent to other countries as the latest weapon in the fight against malaria.

The sterile-insect technique has been used successfully in agriculture and will help reduce the need for spraying insecticides to ward off mosquitoes.

The sterile males mate with females but produce no offspring, so the number of malaria mosquitoes decline in the areas in which they are released.

Unlike female mosquitoes, the males do not drink blood, preferring to live off nectar and rotting plant material.

The Department of Science and Technology and Nuclear Technologies in Medicine’s Biosciences Initiative at the Nuclear Energy Corporation of SA have been working on this project.

But getting the process off the ground is complicated and Lizette Koekemoer, an associate professor at the Wits Research Institute for Malaria at the University of the Witwatersrand, says it is still a long-term goal.

They are planning to build a laboratory in KwaZulu-Natal, where mosquitoes will be bred and sterilised. "The problem is that we are very reliant on funding and we want to do the base research to see if it is safe," Koekemoer says.

The project began in 2010, when Koekemoer and her colleagues started researching at a site in the Kruger National Park. Because it was sometimes difficult to access the site, they moved their research area to Mamfene, a malaria zone in KwaZulu-Natal.

There are two main mosquito species that carry malaria in SA, Anopheles arabiensis and Anopheles funestus. Pyrethroids and DDT insecticide spraying is used in SA to control arabiensis populations, but recently, the species has shown evidence of resistance, says Koekemoer. Funestus usually feeds indoors and is controlled by indoor spraying and the use of insecticide-treated nets.

The sterile-insect technique programme centres on the arabiensis species because its members bite and feed outdoors and, therefore, are not all killed by insecticides.

Koekemoer’s research is focused on three sites in the area. It is a process of understanding the quarry, and working out its weaknesses through intense study.

They collect mosquitoes monthly and screen them to see if they are infected with the malaria parasite.

"Then you get very good baseline information on the species you want to target.

"You need this, because if you want to release males one day, you want to target them when the population is at its lowest," she says.

Currently, no sterilised mosquitoes are being released.

Malaria is still one of the world’s biggest killers. According to the World Health Organisation, nearly 500,000 deaths were attributed to the disease in 2015.

Sterile-insect technique is not a new technology; it has been used extensively in the private sector. It helped in the elimination of the American screw-worm fly and is used to curb fruit fly populations in orchards. But if the malaria project is successful, it would be a first for a government-run programme.

"It hasn’t been done with malaria, because malaria is complicated. Countries that are affected by malaria, are also often not politically stable and financial resources are limited," says Koekemoer.

India did attempt a malaria programme using a sterile-insect technique, but it was a disaster. "Their project almost went into operation, but failed because of political reasoning … when somebody said it was bioterrorism," Koekemoer says.

"This is the reason for the importance of education."

There are many reasons sterile-insect technique is needed in the fight against malaria and other diseases, according to malaria expert Prof Lucille Blumberg.

"We need to look for innovative malaria-control methods, because there is insecticide resistance, which is an ongoing problem and I guess insect-sterile technique is one of them. So, it is part of a greater package," Blumberg says.

This package is likely still to include DDT, indoor spraying and the use of nets.

If the laboratory is built in KwaZulu-Natal, it might not be just swarms of sterile male mosquitoes coming off the production line; other disease-carrying male insects could also end up in line for the radiation snip.

Zimbabwe could one day be ordering sterile male tsetse flies from SA in its effort to control sleeping sickness.

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