Residual Longevity of Recaptured Sterile Mosquitoes as a Tool to Understand Field Performance and Reveal Quality

Invasive mosquito species, such as Aedes albopictus, pose significant threats to both ecosystems and public health due to their role in transmitting diseases, such as dengue, Zika, and chikungunya. The Sterile Insect Technique (SIT) is a promising vector control strategy aimed at reducing mosquito populations by releasing sterile males to mate with wild females and reduce their reproduction rates. In this study, we employed the captive cohort method, which assesses the remaining longevity of randomly caught released individuals, to assess the longevity and frailty dynamics of sterile and non-sterile Ae. albopictus males. Using a mark–release–recapture approach (MRR), we compared the residual lifespan of sterile and non-sterile released males with that of wild, non-sterile males, aiming to understand the frailty dynamics of released males and, therefore, their quality and field performance. Contrary to expectations, our results revealed that released sterile males showed increased longevity compared to non-sterile males. Further, the marking process did not impact the longevity between lab-kept and marked males, suggesting that the marking process does not adversely affect survival under controlled conditions. These findings underscore the importance of optimizing pre-release and mass-rearing practices to enhance the effectiveness of SIT programs. Our study also demonstrates for the first time the use of the captive cohort method for understanding the biological dynamics of sterile mosquito populations in SIT programs, providing valuable insights for improving vector control strategies.

Simple Summary: The current study focused on understanding the longevity and frailty of sterile, non-sterile, and wild male mosquitoes subjected to different treatments, using the novel captive cohort method. Key findings include that marking mosquitoes, following IAEA protocols, had an insignificant effect on longevity under controlled conditions, and that sterilization had no negative effect on male longevity. Moreover, we recorded that exposure to the wild increased post-capture longevity, particularly for sterile males, with longer time in the wild correlating with extended lifespan. Interestingly, the wild experience seems to benefit sterile males more than non-sterile ones, possibly due to demographic selection or hormetic effects. This suggests a possible advantage in field performance for sterile males, which is a key consideration for SIT programs. These findings underscore the importance of ongoing research to optimize rearing, sterilization, and transportation methods for sterile males, ultimately enhancing their performance and longevity in field applications.