Since the 1950s, scientists have used radiation to sterilize insects, which are then released into the wild to mate, but no offspring are produced. Known as the sterile insect technique (SIT), this insect-control method has traditionally relied on gamma rays to sterilize the insects. However, due to concerns about terrorism, gamma-ray irradiators have become increasingly difficult to purchase, transport, and reload.
In order to overcome this limitation, scientists at the International Atomic Energy Agency have developed a way to use X-rays instead. Their research was recently published in the Journal of Medical Entomology.
“A low energy X-ray irradiator may offer a good alternative as it presents several positive characteristics: discontinuous emission of radiation, no radioactive waste, and lower transport costs,” they wrote. “The X-ray irradiator also fulfills the basic requirements for its use in SIT programs, as they are easy to hold in an insect rearing facility, it can be used continuously for several hours, and is easy to operate with minimal training.”
The insect they decided to use for testing was the Asian tiger mosquito (Aedes albopictus), which has been known to spread dengue fever and several other arboviral diseases, such as chikungunya, West Nile virus, La Crosse encephalitis, and Ross River virus.
To successfully irradiate a high number of mosquito pupae, the scientists first developed a multi-layer, stackable device that was described two years ago in the Journal of Medical Entomology.
Using the device and the X-rays, the researchers were able to sterilize as many as 200,000 mosquito pupae at a time with relative ease, and the sterility results were comparable with those achieved by gamma irradiation, where 99% sterility is induced with a dose of 40 Gy.
The lifespan of male mosquitoes decreased after exposure to the X-rays, but this too is similar to what happens when males are irradiated with gamma rays.
Females irradiated at 40 Gy were 100% sterile, and failed to lay any eggs.
“Overall, it was found that the X-ray irradiator is generally suitable for the sterilization process for sterile insect technique programs, as it showed a high processing capacity, practicality, high effectiveness, and reproducibility,” according to the authors.
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