a technology that sterilizes mosquitoes through exposure to radioactivity is a new weapon in the efforts to combat the Aedes aegypti vector of transmission of the dengue virus, chikungunya and zika in Brazil.
the proposal comes from the United Nations agency that coordinates nuclear energy, the International Atomic energy Agency (IAEA), and should be discussed in a meeting in Brasilia on 22 and 23 this month.
the UN agency is providing knowledge transfer and expect to see the technique of application give results within a year after its adoption, told BBC Brazil the deputy director of the organization and head of the department of Nuclear Sciences and Applications, the Brazilian Aldo Malavasi.
in the sterilization proposed by the IAEA, the male mosquitoes of the Aedes aegypti are exposed to radiation ionizing electromagnetic gamma rays. Radiation randomly damages the genetic material contained in the insect semen, causing infertility. When irradiated males mate with females, pups generated are eggs not revenge.
“You loose bugs are normal in their behavior, only that the sperm is not normal, it is broken apart. When the female egg receives the sperm, the embryo can not develop and these eggs are tainted, “said Jorge Hendrichs, head of the pest control department of the IAEA.
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the technology is being tested in Fernando de Noronha by Fiocruz Pernambuco and the Federal University of Pernambuco (UFPE). Already been released 27,000 mosquitoes on the island. With the use of this technique in laboratory tests, only 30% of the eggs became larvae of mosquitoes. The researchers now want to know if this decline will be repeated in nature.
A survey by the Center for Nuclear Energy in Agriculture (CENA), USP also began testing the technology in 2012, but was discontinued for lack of funds. According to the researcher Valter Arthur, coordinator of the research, it will resume this year after increasing interest in the subject because of the association pointed between zika and malformations in babies.
The method is an alternative that is part of the concept SIT (Sterile Insect Technique, or technique of the Sterile Insect). The SIT is a broad definition that encompasses various sterilization techniques, which in common employ the strategy to combat a population “flooding” the environment with sterile individuals.
The IAEA has for years a program together with the FAO, the UN agency for food, develop radioactivity applications against rural plagues.
Security
Malavasi says the technique is harmless to people, despite dealing with radiation. According to him, this is not a radiation contamination risk, but rather something akin to an electromagnetic wave.
“If you do an X-ray at the dentist, you return to radioactive house? Ray passed you by and left. (…) When you cook with the microwave the food is radiation? No. This is the same thing. It is completely safe, “Malavasi said.
There are several ways electromagnetic radiation. They differ only in frequency and wavelength. Among these forms are heat waves, radio waves, infrared light, ultraviolet light, X-rays and gamma rays.
Only the high frequency of the electromagnetic spectrum is considered ionizing. It is in this part of the scale are the gamma rays and “X”, able to generate genetic changes.
But for the researcher Marcelo Firpo, the National School of Public Health Sergio Arouca, of the Oswaldo Cruz Foundation, the new technique demands attention.
“I do not know the deeply technical, but in principle all use of ionizing radiation involving technology is problematic because all ionizing radiation is potentially carcinogenic,” he says.
Firpo, who is coordinator of the Group Health and Environment Abrasco (Brazilian Association of Collective Health), argues that the focus should not be the “elimination of the mosquito, but the continuous elimination of mosquito breeding sites.”
that would be to pass by sanitation measures, improvement of water supply and poverty reduction.
Other criticisms of the method pass by the amount of mosquitoes to be released so that the measure is effective.
SIT technique requires that the number of the environment is changed males released far superior to wild. Only with the “flood” of 20 sterile males for each wild is that females have a good chance to copulate with the tainted insect.
Malavasi recognizes that the use of SIT is an addition to vector control techniques traditional and alone can not end the Aedes aegypti . Therefore, the IAEA recommends it to be used in small communities and in conjunction with traditional methods of sanitary control.
Clean Solution
According to Hendrichs, the use of SIT is a clean solution because it leaves no mark on the environment, compared to fogging the genetically modified mosquitoes.
“There is no persistence in the environment. It is the most user-friendly method because in time you want to stop, (the impact) today. in some other approaches, something remains in the population. We, as the United Nations, not promote it, “said Hendrichs the BBC Brazil.
According to the researchers another advantage compared to pesticides is that the SIT only impacts a particular species. With fumigation chemicals exterminate several species at the same time.
Malavasi stressed that the transgenic mosquitoes differ from the SIT technique had foreign genes inserted into your code.
Also the application of GM is more complex because it involves legislation and control. In Brazil, genetically modified mosquitoes are being produced in Bahia in a factory of Moscamed and Oxitec companies. Before serving in the UN, Malavasi was director of this operation.
History
The SIT technique has been studied for over 60 years and has been tested in several species of flies, butterflies, mosquitoes and other insects.
It has been applied on a large scale for the first time in the southern US in 1950 to combat hominivorax Cochliomyia , parasitic fly whose larvae attack live animals of hot blood, which leads to large losses in cattle herds.
previous tests with the Aedes aegypti took place in India in 1975, and in Kenya, in the same decade.
in New Delhi mosquitoes were sterilized by exposure to Thiotepa, an alkaline agent used in chemotherapy, according to the book Sterile Insect Tecnique:. Principles and Practice in Area-Wide Integrated Pest Management , edited by VADyck, J.Hendrichs and ASRobinson
BBC Brazil, IAEA said tests with Aedes aegypti via gamma radiation have occurred in Indonesia and the results were “encouraging”. Tests with a similar species, the Aedes albopictus , and the same beams are taking place in Italy and in Mauritius.
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