Cuba’s plan to use the sterile insect technique to tackle the spread of dengue—a viral, mosquito-borne disease—relies on expertise and technology from the International Atomic Energy Agency. The technique is not new, having been used to control different insect-vector diseases in diverse regions of the world.
The sterile insect technique relies on nuclear technology to irradiate insects and render them sterile before they are released to mate with wild, disease-carrying insects, reducing the insect population. Supported through the IAEA’s technical cooperation program and in cooperation with the Food and Agriculture Organization of the United Nations (FAO), a pilot trial of a SIT campaign in a Havana neighborhood reduced mosquito (Aedes aegypti) numbers by up to 90 percent in 2021, and early reports indicate that cases of mosquito-borne diseases were eliminated in the last two months of the trial. The IAEA tells the story in a January 13 news article.
The threat of dengue: A growing problem in Cuba and in most tropical countries, dengue is a viral infection that causes high fever, muscle and joint pains, skin rashes, and, in the most severe cases, death. Globally, the number of dengue cases reported to the World Health Organization has increased eightfold over the past two decades, according to the IAEA.
“In Cuba, controlling Aedes aegypti is a national priority,” said René Gato Armas, an entomologist and head of the SIT group at Cuba’s Pedro Kourí Tropical Medicine Institute. “After a major dengue epidemic in 1981, the government deployed an intensive national program based on conventional methods which almost eradicated the mosquito in the late 1980s. Since then, however, epidemic outbreaks from imported cases have been frequent. Currently, dengue is considered an endemic disease in Cuba.”
Nuclear technology—the environmentally friendly alternative: First developed in the United States over 60 years ago, the sterile insect technique has been successfully used to control fruit flies and other insect species while reducing the use of pesticides. As a species-specific form of population control, it does not release non-native species into an ecosystem.
Sterile insect technique campaigns rely on sterilizing mass-reared male insects with irradiation from gamma rays or X-rays so that, while they can mate with wild, disease-carrying female insects, they cannot produce offspring. According to the IAEA, Gato Armas worked closely with experts at the IAEA and the FAO for five years to collect baseline data and develop the pilot SIT trial as an alternative to other mosquito control efforts.
“Dissatisfaction with other mosquito population control techniques, such as sanitary inspection, larvae control, and insecticides, has drawn the government to the [technique] and lets sterilized mosquitoes do most of the work,” said Gato Armas. He explained that the indiscriminate use of insecticides has also triggered resistance to insecticides in Aedes aegypti.
Implementation: Conducted between April and August 2020, the pilot trial covered an area of 50 hectares in an isolated neighborhood of southwest Havana called El Cano. Arroyo Arenas, another neighborhood of similar size, was used as an untreated control site. A focus on communication with members of the pilot trial communities was supported by family doctors and community leaders, who highlighted that the release of sterile male mosquitoes—that do not carry disease or feed on blood—was safe, Gato Armas said.
“Using the SIT for mosquitoes is relatively new anywhere in the world, and pilot trials like this one show how promising they can be,” said Rui Cardoso Pereira, head of the Insect Pest Control Section at the Joint FAO/IAEA Centre, who is working with Gato Armas and others in Cuba to build expertise and scale-up the project. For Cuba’s pilot trial, almost 1.3 million sterile male mosquitoes were released in 21 weeks, and the goal in the near future is to scale up the trial with a larger area and consequently many more sterile mosquitoes.”
IAEA support: The IAEA helped equip Cuba with mosquito-rearing facilities and with the technology needed to separate male and female mosquitoes ahead of irradiation and release. The IAEA also supported training for Cuban program participants in Brazil, Colombia, and Mexico, and at the IAEA laboratories in Austria.
“While staff and space for breeding mosquitoes was provided by the Cuban government, [the technique] requires specialized equipment and expertise, and this is where the IAEA could help,” said Raquel Scamilla Andreo Aledo, the IAEA’s program management officer for Cuba.