UN to test impact of mosquito sterilization on disease spread

The UN says it is preparing to test a sterilization technique targeting mosquitoes that could help rein in the spread of a range of devastating diseases such as dengue and Zika.

A form of insect "birth control", called Sterile Insect Technique (SIT), has been used for decades to control crop-killing pests like fruit flies and moths.

Now it is being evaluated in a species of mosquito as a potential key tool in halting the spread of human diseases.

"It could be really, really significant," Florence Fouque, a scientist at the UN's Special Program for Research and Training in Tropical Diseases (TDR), told reporters on Thursday.

TDR has partnered with the World Health Organization, the International Atomic Energy Agency and the Food and Agriculture Organization to develop a pilot program for countries interested in using SIT on mosquitoes to test the impact on disease transmission.

Fouque said a number of countries were being evaluated and that the participants should be chosen in early 2020 for tests lasting several years.

The mosquitoes targeted are a type that is particularly difficult to control called Aedes albopictus -- more popularly known as the Asian tiger mosquito -- which are a major vector for diseases, including Zika, dengue and chikungunya.

Researchers have found a way to sterilize male mosquitoes using radiation and tests have shown they can thus significantly reduce the population size.

The tests will start as the number of cases of dengue especially explodes, with the disease now seen threatening about half of the world's population.

Raman Velayudhan of the UN health agency's Neglected Tropical Diseases division told reporters that three million cases of dengue are reported from some 110 countries each year.

"But this year we may go beyond 3.5 or even four million cases, because the number has increased dramatically," he said, stressing that only around 20 percent of cases are ever reported, so the disease burden is far higher.

While it is expected to take several years to obtain enough data to reach a clear conclusion on the impact on the spread of human diseases, experts voiced optimism the technique would prove highly effective.

"From the WHO's point of view, one of our realistic goals is to reduce the number of (dengue) cases by at least 25 percent from 2025 to 2030," Velayudhan said.

SIT works by releasing radiation-sterilized male mosquitoes into an environment to mate with wild females, reducing the size of the population over time as females fail to reproduce.

Tests have already shown that the technique can reduce mosquito populations by more than 90 percent, but it remains unclear if this could translate into fewer human infections.

"We already have evidence that SIT is able to reduce the density of mosquitoes very significantly," said Jeremy Bouyer, a medical entomologist in a joint FAO/IAEA division for Nuclear Techniques in Food and Agriculture.

"Now we must prove that it will also impact the transmission of the disease," he told reporters.

There were initially concerns that SIT reduced the mating competitiveness of the test mosquitoes as well as their survival rates, undermining the technique's effectiveness.

But Bouyer insisted the technique has been refined, noting also that small drones had been developed to gently release sterile mosquitoes into wild populations.

(Source: AFP)

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