Abstract
The global expansion of Aedes albopictus together with the absence of vaccines for most of the arboviruses transmitted by this mosquito has stimulated the development of sterile-male strategies aiming at controlling disease transmission through the suppression of natural vector populations. In this context, two environmentally friendly control strategies, namely the Sterile Insect Technique (SIT) and the Wolbachia-based Incompatible Insect Technique (IIT) are currently being developed in several laboratories worldwide. So far however, there is a lack of comparative assessment of these strategies under the same controlled conditions. Here, we compared the mating capacities, i.e. insemination capacity, sterilization capacity and mating competitiveness of irradiated (35 Gy) and incompatible Ae. albopictus males at different ages and ratios under laboratory controlled conditions. Our data show that there was no significant difference in insemination capacity of irradiated and incompatible males, both male types showing lower capacities than untreated males at 1 day but recovering full capacity within 5 days following emergence. Regarding mating competitiveness trials, a global observed trend is that incompatible males tend to induce a lower hatching rate than irradiated males in cage controlled confrontations. More specifically, incompatible males were found more competitive than irradiated males in 5:1 ratio regardless of age, while irradiated males were only found more competitive than incompatible males in the 1:1 ratio at 10 days old. Overall, under the tested conditions, IIT seemed to be slightly more effective than SIT. However, considering that a single strategy will likely not be adapted to all environments, our data stimulates the need for comparative assessments of distinct strategies in up-scaled conditions in order to identify the most suitable and safe sterilizing technology to be implemented in a specific environmental setting and to identify the parameters requiring fine tuning in order to reach optimal release conditions.
Highlights
The Asian tiger mosquito Aedes albopictus has emerged as a mosquito species of major medical concern following its global expansion over the past 30–40 years [1,2,3] and its recent involvement in several arboviral epidemic outbreaks
Irradiated and incompatible males have lower insemination capacities at emergence The insemination rates of wild type LR females caged for 24 h with wild type LR males, irradiated LRi males or incompatible ARwPLR males were examined by assessing the percentage of inseminated females and the percentage of females with 0, 1, 2 or 3 filled spermathecal capsules
We propose an alternative approach: Incompatible Insect Technique (IIT) implementation requires a surveillance of Wolbachia infection in treated populations all over releases, and the appearance of any sign of population replacement may be overcome by the release of irradiated males
Summary
The Asian tiger mosquito Aedes albopictus has emerged as a mosquito species of major medical concern following its global expansion over the past 30–40 years [1,2,3] and its recent involvement in several arboviral epidemic outbreaks. Aedes albopictus is a proven competent vector, in laboratory tests, for over 20 arboviruses including Dengue and Chikungunya viruses [4] and has been shown to be the main vector in a Chikungunya epidemic that hit La Réunion Island in 2005–2006 [5] and Italy in 2007 [6]. This aggressive day-biting mosquito has spread worldwide from its native range in South-East Asia [7, 8] probably mainly disseminating through the international trade of used tires [9]. Their use is increasingly impaired by negative effects on non-targeted organisms and on the environment together with the rapid selection of resistance in insect natural populations [13,14,15], stimulating the development of innovative control methods
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