Investigating the effects of low temperature and compaction on the quality of adult radio-sterilised Aedes albopictus (Diptera: Culicidae) males in view of their optimal transport to the pilot sterile release site in Mauritius

Abstract

The Sterile Insect Technique (SIT) is currently being investigated against Aedes albopictus Skuse (Diptera: Culicidae) mosquitoes in Panchvati, a village in Mauritius. As an essential step before field releases, this study investigated the effect of temperature (2 h exposure at 5, 10, 15 or 25 °C) and compaction (2000 males per 1062 or 8553 cm3) on the fitness of radio-sterilised Ae. albopictus males with the aim of optimising their transport from the mosquito-production unit to the release site in Panchvati. Temperature and compaction had no significant effect on male survival during the first fifteen days. However, when survival was assessed over twenty-five days, males stored at 25 °C had significantly higher survival rates than males stored at lower temperatures (Kaplan-Meier: P < 0.05). Furthermore, males stored at 5 °C survived significantly longer than those stored at 10 °C or 15 °C (Kaplan-Meier: P < 0.05). Considering the fact that a weekly release of sterile males is planned in Panchvati, the long-term negative effect of low temperatures (5 to 15 °C) on male survival, may have limited relevance in the field. Male storage at 5 °C for 2 h in compacted conditions, were hence further investigated. Compaction significantly impacted male competitiveness, with a mean competitiveness index of 0.2 when sterile males were stored at 2000 males per 1062 cm3. Two thousand males per Bugdorm cage (27,000 cm3), was found to be the optimal density at which sterile Ae. albopictus males could be stored and transported by van to Panchvati, with minimal effects of the latter’s survival and competitiveness.