Abstract
BackgroundAedes 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 its control mainly relies on the use of biocides. Data on the species’ resistance status are essential for efficient and sustainable control. To date the insecticide resistance status of Ae. albopictus populations from Greece against major insecticides used in vector control remains largely unknown.MethodsWe investigated the insecticide resistance status of 19 Ae. albopictus populations from 11 regions of Greece. Bioassays were performed against diflubenzuron (DFB), Bacillus thuringiensis var. israelensis (Bti), deltamethrin and malathion. Known insecticide resistance loci were molecularly analysed, 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.ResultsBioassays showed full susceptibility to DFB, Bti and deltamethrin, but resistance against the OP malathion (range of mortality: 55.30–91.40%). VGSC analysis revealed a widespread distribution of the mutations F1534C (in all populations, with allelic frequencies between 6.6–68.3%), and I1532T (in 6 populations; allelic frequencies below 22.70%), but absence of V1016G. CCE gene amplifications were recorded in 8 out of 11 populations (overall frequency: 33%). Co-presence of the F1534C mutation and CCEae3a amplification was reported in 39 of the 156 samples analysed by both assays. No mutations at the CHS-1 I1043 locus were detected.ConclusionsThe results indicate: (i) the suitability of larvicides DFB and Bti for Ae. albopictus control in Greece; (ii) possible incipient pyrethroid resistance due to the presence of kdr mutations; and (iii) 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 programmes.
Highlights
In the last two decades southern European countries have suffered from a number of vector-borne diseases (VBDs), such as chikungunya (CHIKV), dengue (DENV) and West Nile virus (WNV) outbreaks [1, 2]
Insecticide susceptibility bioassays Larval bioassays Following the World Health Organization (WHO) guidelines for laboratory and field testing of mosquito larvicides [37], we examined the susceptibility of Ae. albopictus populations against two larvicides; the bacterial larvicide Bacillus thuringiensis var. israelensis (Bti) (VectoBac12AS, Valent BioSciences LLC, Illinois, USA; 1200 international toxic units (ITU)/mg; 11.61% w/v) and the insect growth regulator DFB (DU-DIM 15SC, Arysta LifeScience, Amsterdam, The Netherlands; 15% w/v)
The calculated LC50 values were below 0.20 mg/l for all populations (Table 2), which is less than the LC50 values reported for susceptible Ae. albopictus laboratory strains in other studies
Summary
In the last two decades southern European countries have suffered from a number of vector-borne diseases (VBDs), such as chikungunya (CHIKV), dengue (DENV) and West Nile virus (WNV) outbreaks [1, 2]. This has been attributed to several factors including the introduction and establishment of invasive vector species, associated with the ongoing environmental and climate change and the globalization of human activities [3]. Aedes albopictus was first recorded in Europe in 1979 [6] and to date displays a wide-spread distribution in the Mediterranean region while reported in northern European countries [7]. To date the insecticide resistance status of Ae. albopictus populations from Greece against major insecticides used in vector control remains largely unknown
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