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Sterile Insect Technique Used to Supress Mosquito Disease Vectors in Florida

Sterile Aedes aegypti males inside a bucket ready for release on Captiva Island, Lee County, Florida, USA (Source: LCMCD, USA).

Sterile Aedes aegypti males inside a bucket ready for release on Captiva Island in Lee County, Florida. (Photo: LCMCD, USA).

Sterile mosquitoes are being used to suppress mosquitoes that have become resistant to insecticide in Fort Myers, Florida in the United States of America. The pilot project is being carried out with the support of experts from the IAEA and the Food and Agriculture Organization (FAO),  and aims to suppress populations of a disease-vector species of mosquito called Aedes aegypti which is  prevalent in Florida.

Aedes aegypti mosquito populations are particularly difficult to manage using traditional control techniques as they are diurnal mosquitoes that use cryptic breeding habitats, which makes their larvae difficult to find and remove. In addition, these mosquitoes are becoming increasingly resistant to insecticides. The Lee County Mosquito Control District (LCMCD), located in southwest Florida, USA, has been working to mitigate the public health threat posed by these mosquitoes since its inception in 1958. Increasing urbanization combined with increasing resistance to insecticides has led to a nearly ubiquitous spread of Ae. aegypti throughout the county and created a need for the LCMD to identify alternative ways to combat this challenging species.

A new pilot project involving the Sterile Insect Technique (SIT) is now being used to suppress populations of disease vector mosquitoes in Fort Myers Florida. The SIT is an environmentally friendly pest control method which involves sterilizing male insects using radiation, before releasing them to mate with wild females, resulting in fewer or no offspring. The SIT pilot project is benefiting from extrabudgetary funding contributions from the IAEA’s Peaceful Uses Initiative (PUI).

Rui Cardoso Pereira, Head of the Insect Pest Control at the Joint FAO/IAEA Centre of Nuclear Techniques in food and Agriculture, says “the extrabudgetary PUI funds contributed by the USA have been instrumental for R&D based improvement of the SIT package for Aedes mosquitoes and its further transfer to pilot projects in our Member States.” Aedes aegypti mosquitoes can spread diseases such as chikungunya, dengue, yellow fever and Zika, making them a significant threat to public health and therefore contributes to the attainment of Sustainable Development Goal 3, good health.

Releases of sterile mosquitoes being conducted at the Captiva Island, FL, USA

Releases of sterile mosquitoes being conducted at the Captiva Island. (Photo: LCMCD)

The SIT pilot project, which was initiated n the coastal city of Fort Myers, has already been tested out on Captiva Island in Florida, around 30 miles away, during a successful pilot project between 2020 and 2022. Male mosquitoes were mass-reared and sterilized before being released to mate with wild females. At the peak of releases, approximately 400 000 sterile males were released per week in Captiva Island. The releases led to a significant reduction of the population in the first year, 2020, and complete suppression in 2021 and 2022. Scientists were able to compare ecological indexes between Sanibel Island (the control area) and Captiva Island, where the sterile mosquitoes were released. Rachel Morreale, Manager of the Applied Science and Technologies Department at LCMCD, stated “it was remarkable to see the impacts that our sterile male releases had on the population of Ae. aegypti on Captiva.” 

Hurricane Ian devastated both Captiva and Sanibel islands completely in September 2022, making it impossible to access by car, and putting an end to the pilot project.

The damage caused was so significant that LCMCD determined that the best course of action would be to move the release programme to a new area on the mainland. Using lessons learned from the pilot project on Captiva Island, LCMCD collected baseline data to better inform their releases of sterile male Ae. Aegypti in Fort Myers, which was initiated in February 2024. While the move to this new area was sooner than initially planned, the pilot project on Captiva Island allowed LCMCD to validate SIT as a component of an integrated mosquito management operation for the County. Using the knowledge gained from mass-rearing, releases, and fieldwork, LCMCD is hopeful to have similar successful outcomes in Fort Myers and provide relief and protection to local residents.

According to David Hoel, Executive Director of LCMCD, “the unique attributes of this programme and technical expertise provided to us by the IAEA is enabling LCMCD to gain a foothold in suppression of this mosquito which is difficult at best to control by conventional mosquito control techniques and shows great promise for future prevention of mosquito-borne disease threat in Lee County, Florida.”

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