Modelling the impact of sterile male releases on a wild mosquito population – model assessment from field trials in Mauritius

Mosquito control remains the cornerstone of the prevention and control of diseases caused by Aedes-borne pathogens, such as dengue, chikungunya and Zika viruses. An innovative vector control method adapted to Aedes albopictus mosquitoes is the Sterile Insect Technique (SIT), which consists of the mass-release of sterilized male mosquitoes. The impact of SIT and the optimization of release strategies can be studied through modelling. The objective of this study was to evaluate the ability of a mathematical model to simulate the impact of SIT releases by comparing the simulation outputs with entomological data collected during and after SIT trials in Mauritius. We modified a model of Ae. albopictus population dynamics (ARBOCARTO) that incorporates variations in temperature and rainfall, as well as the availability of breeding sites to introduce SIT. We then simulated SIT releases under the same conditions as the field trials and assessed the model's ability to realistically reproduce the impact of SIT releases by comparing the simulation outputs with entomological data observed in a trial site (where SIT releases were performed between May 2017 and February 2018) and a control site (without SIT releases). Four simulation scenarios were considered: without SIT, and with SIT applied on 50%, 75% and 100% of the trial area. Results showed that the ARBOCARTO model reproduced the major trends in the intra-annual Ae. albopictus population variations: simulated abundances of eggs, based on weather conditions, were highly and significantly correlated with the egg abundances observed at the SIT control site. The model also matched the trial site data for both the predicted number of newly produced eggs and the percentage of fertile eggs. The simulation results also revealed the importance of the percentage of the area covered by SIT releases as a key parameter for SIT impact, both for the reduction rate and for the resilience time, defined as the time required after the end of releases for the mosquito population to return to its initial state. Thanks to its user-friendly interface, the ARBOCARTO model can be used by vector control services and health stakeholders to simulate the impact of SIT releases and optimize release strategies, taking into account the operational capacity of sterile mosquito rearing facilities and the environmental conditions of the releases.