Larval application of sodium channel homologous dsRNA restores pyrethroid insecticide susceptibility in a resistant adult mosquito population

Abstract

BackgroundMosquitoes host and pass on to humans a variety of disease-causing pathogens such as infectious viruses and other parasitic microorganisms. The emergence and spread of insecticide resistance is threatening the effectiveness of current control measures for common mosquito vector borne diseases, such as malaria, dengue and Zika. Therefore, the emerging resistance to the widely used pyrethroid insecticides is an alarming problem for public health. Herein we demonstrated the use of RNA interference (RNAi) to increase susceptibility of adult mosquitoes to a widely used pyrethroid insecticide.MethodsExperiments were performed on a field-collected pyrethroid resistant strain of Ae. aegypti (Rio de Janeiro; RJ). Larvae from the resistant Ae. aegypti population were soaked with double-stranded RNAs (dsRNAs) that correspond either to voltage-gate sodium channel (VGSC), P-glycoprotein, or P450 detoxification genes and reared to adulthood. Adult mortality rates in the presence of various Deltamethrin pyrethroid concentrations were used to assess mosquito insecticide susceptibility.ResultsWe characterized the RJ Ae. aegypti strain with regard to its level of resistance to a pyrethroid insecticide and found that it was approximately 6 times more resistant to Deltamethrin compared to the laboratory Rockefeller strain. The RJ strain displayed a higher frequency of Val1016Ile and Phe1534Cys substitutions of the VGSC gene. The resistant strain also displayed a higher basal expression level of VGSC compared to the Rockefeller strain. When dsRNA-treated mosquitoes were subjected to a standard pyrethroid contact bioassay, only dsRNA targeting VGSC increased the adult mortality of the pyrethroid resistant strain. The dsRNA treatment proved effective in increasing adult mosquito susceptibility over a range of pyrethroid concentrations and these results were associated with dsRNA-specific small interfering RNAs in treated adults, and the corresponding specific down regulation of VGSC gene expression level. Finally, we demonstrated that the efficiency of our approach was further improved by ‘tiling’ along the VGSC gene in order to identify the most potent dsRNA sequences.ConclusionsThese results demonstrate that dsRNA applied to mosquito larvae retains its biological activity into adulthood. Thus, the RNAi system reported here could be a useful approach to control the widespread insecticide resistance in mosquitoes and other insect vectors of human diseases.Electronic supplementary materialThe online version of this article (doi:10.1186/s13071-016-1634-y) contains supplementary material, which is available to authorized users.

Habitat productivity and pyrethroid susceptibility status of Aedes aegypti mosquitoes in Dar es Salaam, Tanzania

“…To our knowledge, this is the first study to demonstrate the susceptibility status of A. aegypti against different registered pyrethroids in Tanzania and there are limited data to compare our findings with. In other countries, studies have found detailed mechanisms that are involved in the different insecticides resistance, which is also needed to be done in Tanzania for strategic control of A. aegypti as in Thailand and Brazil [33, 34]. …”

Sodium Channel Mutations and Pyrethroid Resistance in Aedes aegypti

“…However, the V1016G mutation has not been reported in Latin America [31,32,46,47]. Instead, mutation V1016I was found, and often coexists with F1534C in South and North America, such as Venezuela [48], three French overseas territories [49], Brazil [50,51,52], Mexico [53], and the USA [54]. More recently, V1016I and F1534C were detected in Ghana, Africa [55], and a new mutation, T1520I, was found along with the F1534C mutation in a population in India [56].…”

“…So far, V1016G has been detected only in Southeast Asia [34,37,40,41,44,45], whereas V1016I is distributed in South and North America [48,49,50,51,52,53]. More recently, V1016G, along with F1534C, was also detected in Ghana.…”

Implementing the sterile insect technique with RNA interference – a review

“…Larvae are simple to target with eRNAi by ingestion as they eat steadily, volubly, and are generally less mobile than adults (hence can naturally take up dsRNA that is concentrated within local food sources). For aquatic larvae, dissolving dsRNA in solution and bathing the larvae within it, is the most common method of effecting gene silencing via eRNAi (Figueira-Mansur et al, 2013;Singh et al, 2013;Whyard et al, 2015;Bona et al, 2016). dsRNA can be delivered to non-aquatic larvae: (1) topically via droplet feeding (Toprak et al, 2013), (2) by inducing the larvae to feed upon dsRNA-expressing transgenic plants (Xiong et al, 2013;Mamta et al, 2015;Tian et al, 2015;Hu et al, 2016), (3) by feeding larvae dsRNA-expressing transgenic bacteria (Zhu et al, 2011;Yang & Han, 2014;Li et al, 2015c), and (4) by feeding larvae naked dsRNA overlaid onto an artificial diet (Asokan et al, 2014;Yang & Han, 2014;Hu et al, 2016).…”

“…In this context, the development of new methods for insect control is of key importance and there has been intense interest in the utility of gene silencing methods induced by RNA interference (RNAi). RNAi can induce mortality (Yang & Han, ; Cao et al., ; Abd El Halim et al., ; Christiaens et al., ; Hu et al., ; Malik et al., ), create beneficial phenotypes for insect control (Salvemini et al., ; Shukla & Palli, ; Peng et al., ; Yu et al., ), and prevent pesticide resistance in insect pests (Figueira‐Mansur et al., ; Guo et al., ; Wei et al., ; Bona et al., ; Sandoval‐Mojica & Scharf, ). Therefore, the potential for RNAi as a basis for future pest management strategies holds great promise (Huvenne & Smagghe, ; Gu & Knipple, ; Scott et al., ; Baum & Roberts, ; Kim et al., ).…”