Phenotypic and molecular analysis of insecticide resistance in Aedes albopictus populations from Greece

Abstract Background: Aedes albopictus has a well-established presence in southern European countries, associated with recent disease outbreaks (e.g. Chikungunya). Development of insecticide resistance in the vector is a major concern as it’s control mainly relies on the use of biocides. Data on the specie’s resistance status is essential for efficient and sustainable control. Methods: We investigated the insecticide resistance status of several Ae. albopictus populations from Greece. Bioassays were performed against diflubenzuron (DFB), B. thuringiensis var. israelensis (Bti), deltamethrin and malathion. Molecular analysis of known insecticide resistance loci was performed, i.e. voltage-gated sodium channel (VGSC) mutations associated with pyrethroid resistance; presence and frequency of carboxylesterases 3 (CCEae3a) and 6 (CCEae6a) gene amplification associated with organophosphate (OP) resistance and; chitin synthase-1 (CHS-1) for the possible presence of DFB resistance mutations. Results: Bioassays showed full susceptibility to DFB, Bti and deltamethrin, but resistance against the OP malathion. VGSC analysis revealed a widespread distribution of mutations F1534C (in all populations, with allelic frequencies between 6.6% - 68.3%), and I1532T (in 6 populations), but absence of V1016G. CCE gene amplifications were recorded in 8 out of 11 populations. Co-presence of mutation F1534C and CCEae3a amplification was reported in a subgroup of samples. No mutations at the CHS locus I1043 were detected. Conclusions: The results indicate: (i) the suitability of larvicides DFB and Bti for Ae. albopictus control in Greece, (ii) a possible incipient pyrethroid resistance due to the presence of kdr mutations and (iii) a possible reduced efficacy of OPs, in a scenario of re-introducing them for vector control. The study highlights the need for systematic resistance monitoring for developing and implementing appropriate evidence-based control programs. Key words: diagnostic, arbovirus, mosquito tiger, insecticide resistance, vector control, Europe