Known as the Sterile Insect Technique (SIT), the process involves rearing large quantities of sterilized male mosquitoes in dedicated facilities and then releasing them to mate with females in the wild. As they do not produce any offspring, the insect population declines over time.
A technique that sterilizes male
mosquitoes using radiation will soon be tested as part of global health efforts
to control diseases such as chikungunya, dengue, and Zika.
Known as the Sterile Insect
Technique (SIT), the process involves rearing large quantities of sterilized
male mosquitoes in dedicated facilities, and then releasing them to mate with
females in the wild. As they do not produce any offspring, the insect
population declines over time.
The Sterile Insect Technique was
first developed by the U.S. Department of Agriculture and has been used
successfully to target insect pests that attack crops and livestock, such as
the Mediterranean fruit fly and the New World screwworm fly. It is currently in
use globally in the agriculture sector on six continents.
Now, the Special Programme for
Research and Training in Tropical Diseases (TDR) and the International Atomic
Energy Agency (IAEA), in partnership with the Food and Agriculture Organization
(FAO), and WHO have now developed a guidance document for countries that have
expressed interest in using the technique to tackle disease outbreaks
transmitted by the winged insects.
The guidance on using the technique to control diseases in humans recommends adopting a phased approach
that allows time to test the efficacy of the sterilized insects.
Epidemiological indicators monitor the impact of the method on
disease-transmission. It also provides recommendations on mass production of
the sterile mosquitoes, government and community engagement, measuring the
impact of the technique, and assessing cost-effectiveness.
Jeremy Bouyer, a medical entomologist
at the Division of Nuclear Techniques in Food and Agriculture, explains they already
have evidence that the technique is able to reduce the density of mosquitoes
very significantly.
If this is done for long enough, “you will be able to
reduce, and in some cases, eliminate the target population”, He said, adding
that this technique will out-compete the wild males in the field and they will
induce sterility in the females so that their eggs will not hatch, resulting in
the control of the next generation of mosquitoes.
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Highlighting the safety of the irradiation technique, Bouyer insisted that no test tube manufactured genes – known as transgenes –
were being inserted into mosquitoes.
“The mutations we are creating with this system are
random, so we are not transgenic, we are not putting transgenes into the
mosquitoes and they are occurring naturally in the population,” he said. “It’s
just that we have enough mutations to create full sterility in what we release.
But there is no particular concern with what we release, the mosquitoes are not
radioactive, they are just irradiated and thus sterilized.”
More than half the world is now
at risk from mosquito-transmitted dengue fever, according to the World Health
Organization (WHO). Dengue, along with
other diseases transmitted by mosquitoes - malaria, Zika, chikungunya and
yellow fever – account for about 17 per cent of all infectious diseases
globally, claiming more than 700,000 lives each year, and inflicting suffering
on many more.
In recent decades, the incidence
of dengue has increased dramatically due to environmental changes, unregulated
urbanization, transport and travel, and insufficient sustainable vector control
tools and their application. On average, WHO registers three million cases
every year, but they may reach four million in 2019, it said.
If successful, the potential
health benefits could be enormous, Raman Velayudhan, Coordinator, from WHO's
Department of Neglected Tropical Diseases (NTDs) said.
