Bioassay and molecular monitoring of insecticide resistance status in Aedes albopictus populations from Greece, to support evidence-based vector control

Authors: BALASKA, SOFIA - AGRICULTURAL UNIVERSITY OF ATHENS; FOTAKIS, EMMANOUIL - AGRICULTURAL UNIVERSITY OF ATHENS; KIOULOS, ILIAS - AGRICULTURAL UNIVERSITY OF ATHENS; GRIGORAKI, LINDA - LIVERPOOL SCHOOL OF TROPICAL MEDICINE; MPELLOU, SPYRIDOULA - BIOEFARMOGES ELEFTHERIOU & CO LP; CHASKOUPOULOU, ALEXANDRA - EUROPEAN BIOLOGICAL CONTROL LABORATORY (EBCL); VONTAS, JOHN - AGRICULTURAL UNIVERSITY OF ATHENS

Submitted to: Parasites & Vectors
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/20/2020
Publication Date: 6/29/2020
Citation: Balaska, S., Fotakis, E., Kioulos, I., Grigoraki, L., Mpellou, S., Chaskoupoulou, A., Vontas, J. 2020. Bioassay and molecular monitoring of insecticide resistance status in Aedes albopictus populations from Greece, to support evidence-based vector control. Parasites & Vectors. 13:328. https://doi.org/10.1186/s13071-020-04204-0.
DOI: https://doi.org/10.1186/s13071-020-04204-0

Interpretive Summary: Aedes albopictus is an important vector and invasive mosquito species. Originating from the tropical and subtropical regions of southern Asia, it currently displays a worldwide distribution. Being a competent vector of more than 22 arboviruses, including Yellow fever virus, CHIKV and DENV, Ae. albopictus constitutes a major global public health threat. The prevention of mosquito-borne diseases relies to a great extent on vector control, mainly through the utilization of synthetic insecticides. The limited number of approved insecticides for public health purposes and the worldwide data on insecticide resistance generated to date raise concerns regarding the effectiveness and suitability of the current vector control interventions. Insecticide resistance has been reported in Ae. albopictus, yet a big knowledge gap remains in regards to the susceptibility status, geographical distribution, frequency and co-occurrence of resistance traits (underlying mechanisms) in the vector populations. This study represents an extended investigation of the insecticide resistance status of Ae. albopictus in Greece against three major classes of insecticides commonly used across the world: pyrethroids, chitin synthesis inhibitors and organophosphates. The study's results highlight the need for systematic resistance monitoring for developing and implementing appropriate evidence-based control programs. This information will be used by those studying or engaged in mosquito vector management.

Technical Abstract: Aedes albopictus has a well-established presence in southern European countries, associated with recent disease outbreaks (e.g. Chikungunya). Its control relies on the use of biocides, but the development of resistance is a major concern. Data on vector insecticide resistance is essential for efficient and sustainable control. We investigated the insecticide resistance status of several Ae. albopictus populations from Greece. Bioassays against diflubenzuron (DFB), B. thuringiensis israelensis (Bti), deltamethrin and malathion were performed. Molecular analysis of known insecticide resistance loci, 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 resistance and; chitin synthase-1 for the possible presence of DFB resistance mutations, was also performed. Ae. albopictus was the dominant Aedes species. 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 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. 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.