Dec. 15, 2017
By Laura Gil, IAEA Office of Public Information and Communication
Experts use ionizing radiation to sterilize male insects that are mass-produced in special rearing facilities like this one in Mendoza, Argentina. (Photo: L. Gil/IAEA)
After its success in controlling a devastating fruit fly with nuclear technology, Argentina is gearing up to fight a new enemy: mosquitoes that transmit Zika, in addition to dengue and chikungunya.
The method applied in both cases is the sterile insect technique (SIT), an insect birth control method that uses irradiation to sterilize and release insects to suppress pest populations. The IAEA and the Food and Agriculture Organization of the United Nations (FAO) have supported Argentina in applying SIT against fruit flies since the mid-1990s.
Fruit fly success
Argentina has a long history of applying area-wide SIT successfully. Ever since the Mediterranean fruit fly appeared in the country in the 1900s, fruit trade with countries free of the pest was restricted. This resulted in multimillion dollar losses due to quarantine restrictions and costs associated with postharvest treatments required for fruit exports.
Thanks to an eradication programme using an integrated pest management approach that includes SIT and with the technical support of the IAEA and the FAO, plant protection authorities and trading partners declared Patagonia free of this pest in 2005, a status the region has enjoyed since.
As a result, Patagonia’s fruit industry has saved millions of dollars by not having to use post-harvest treatment to kill fruit fly larvae as a prerequisite for exports. The industry, mainly focused on growing pears and apples, generates US $700 million a year, according to the National Food Quality and Sanitation Service (Senasa).
Mediterranean fruit flies in an insect-producing factory in Mendoza, western Argentina. (Photo: L. Gil/IAEA)
SIT has also helped Mendoza — a region in western Argentina famous for its peaches and plums— maintain the fly population at very low levels since 2009.
“I have grown peaches and apricots since 1995,” said Roberto Guirado, a producer in Mendoza. “When the fly came, you could see the damage caused by the larvae in the fruit. Nobody would buy it in the market.” Fruit like the one Guirado produces in Mendoza is usually sold in Buenos Aires and San Luis, but at the time the Mediterranean fruit fly spread, shipments were restricted, resulting in a 30% loss for him. “My fruit was soft, it fell, and it had holes in it as if a needle had pierced it. I wouldn’t have bought any of it myself.”
But thanks to the daily release of sterilized fruit flies, the pest gradually decreased. In his 13 hectare farm, Guirado’s production has returned to its original level. The best part about the technique, he said, was that he didn’t have to apply strong pesticides that could harm the environment or his own health.
Check this photo
essay to see how the sterile insect-rearing facility in Mendoza works.
Argentinean scientists are currently working with the IAEA and the FAO to apply SIT in the northeast of the country, where they have already started trial releases of sterilized fruit flies in pilot areas. The idea is to reduce direct damage to citrus production while also restricting insecticide use.
One good advantage of SIT is that it reduces the need to apply strong pesticides that could harm the environment or people's health. (Photo: L. Gil/IAEA)
“Ideally, we would be creating two large belts of Mediterranean fruit fly-free areas,” said Gustavo Taret, engineer at the Institute of Health and Agricultural Quality in Mendoza, ISCAMEN. “One starting in the north and the other in the south. The idea is to control the fly population in all affected regions, gradually, until both belts meet in the middle.”
Mosquito: the new challenge
After this success, Argentina is looking into the possibility of applying SIT to Zika-transmitting mosquitoes, a possibility that is still at the early research stage.
“We recovered from a fruit pest only to dive into a new problem: Zika,” said Celina Horak, Manager of Radiation Applications at the Argentine Atomic Energy Commission (CNEA).
In 2016, Argentina reported more than 41 000 confirmed cases of dengue, 322 of chikungunya and 21 of Zika, all diseases caused by viruses that are transmitted by the Aedes aegypti mosquito. This year, Zika cases have increased considerably, reaching a peak of 102 suspected cases during week 14.
The Aedes aegypti mosquito transmits Zika, dengue and chikunguya. (Photo: IAEA)
Responding to requests for assistance at the height of the Zika outbreak in 2015, an IAEA technical cooperation project kicked off to help 21 countries in Latin America and the Caribbean, including Argentina, develop the SIT package to suppress Aedes aegypti mosquito populations.
Since the start of the project, Argentina has made significant progress. “We are already conducting studies in cages and laboratory assessments in our mosquito rearing laboratory at the Ezeiza Atomic Centre, and the plan is to do pilot testing in Posadas in 2019,” Horak said.
In the absence of vaccines and efficient, safe and inexpensive drugs to manage Zika and some of the other diseases, SIT may become an option for the region. Reducing the population of this type of mosquito, in addition, may also curtail the spread of other mosquito-borne viruses.
“Zika was a wake-up call,” said Hanano Yamada, entomologist at the IAEA involved in the project. “Probably this is not the last virus that will show up in Latin America, transmitted by Aedes aegypti.”