X-rays and gamma rays do not differ in their effectiveness for sterilizing pupae and adults of the mosquito Aedes aegypti

Authors: CHEN, CHAO - University Of Florida; XUE, RUDY - Anastasia Mosquito Control District; QUALLS, WHITNEY - Anastasia Mosquito Control District; Gibson, Seth; HAHN, DANIEL - University Of Florida

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/2/2025
Publication Date: 3/13/2025
Citation: Chen, C., Xue, R., Qualls, W., Gibson, S., Hahn, D.A. 2025. X-rays and gamma rays do not differ in their effectiveness for sterilizing pupae and adults of the mosquito Aedes aegypti. Journal of Economic Entomology. 1-10. https://doi.org/10.1093/jee/toaf030.
DOI: https://doi.org/10.1093/jee/toaf030

Interpretive Summary: The sterile insect technique (SIT) is emerging as a useful tool for non-chemical control of harmful, disease-transmitting mosquito populations. In the SIT approach, male mosquitoes are reared in a laboratory and sterilized using ionizing radiation from high-activity gamma radioisotope sources. These males are then released into areas where mosquitoes threaten human health. However, gamma irradiators have a number of drawbacks including consumption of expensive materials, costs for security and compliance on existing units, and the regulatory and security burdens associated with reloading existing units or purchasing new units due to potential for misuse of high-activity radioisotopes. One practical alternative is commercially available low-energy X-ray irradiator units. While several studies have shown low-energy X-ray irradiators can be used successfully for SIT applications, differences in both energy spectra and penetration between gamma and X-ray platforms have led to questions about whether the two platforms are equivalent in their efficacy for SIT. Here we compared the effectiveness of a commercially available, low-energy X-ray irradiator, RadSource 2400, and a long-standing gamma irradiator previously used for SIT programs, a Gammacell 1000 Cs-137 unit, for inducing male sterility while maintaining adult performance in the mosquito Aedes aegypti. We found equivalence between both X-ray and gamma sources: both induced 99% sterility in males, and lifespan and mating competitiveness of sterile males was not different between the treatments. Our results show a readily available low-energy X-ray irradiator can easily be used as an alternative to gamma irradiation for Ae. aegypti SIT programs.

Technical Abstract: In addition to a long history of success in agricultural pest management programs, sterile insect technique (SIT) is emerging as a useful tool for integrative mosquito management in many programs worldwide. Males for SIT have typically been sterilized using ionizing radiation from high-activity radioisotope sources, either cobalt-60 or cesium-137. However, gamma irradiators have a number of drawbacks including the short half-life of Co-60, costs for security and compliance on existing units, and the regulatory and security burdens associated with reloading existing units or purchasing new units due to potential for misuse of high-activity radioisotopes. One practical alternative to isotopic irradiators is commercially available low-energy X-ray irradiator units. While several studies have shown low-energy X-ray irradiators can be used successfully for SIT applications, differences in both energy spectra and penetration between gamma and X-ray platforms have led to questions about whether the two platforms are equivalent in their efficacy for SIT. Here we compared the effectiveness of a commercially available, low-energy X-ray irradiator, RadSource 2400, and a long-standing gamma irradiator previously used for SIT programs, a Gammacell 1000 Cs-137 unit, for inducing male sterility while maintaining adult performance in the mosquito Aedes aegypti. We found equivalence between both X-ray and gamma sources; wherein both induced 99% sterility when male pupae were treated around 50Gy and around 75Gy when male adults were treated. Lifespan and mating competitiveness of sterile males was not different for either X-ray or gamma platforms in both pupal and adult irradiation modalities. Our results show a readily available low-energy X-ray irradiator can easily be used as an alternative to gamma irradiation for Ae. aegypti SIT programs.