Combined target site (kdr) mutations play a primary role in highly pyrethroid resistant phenotypes of Aedes aegypti from Saudi Arabia

Abstract

BackgroundPyrethroid resistance is a threat to effective vector control of Aedes aegypti, the vector of dengue, Zika and other arboviruses, but there are many major knowledge gaps on the mechanisms of resistance. In Jeddah and Makkah, the principal dengue-endemic areas of Saudi Arabia, pyrethroids are used widely for Ae. aegypti control but information about resistance remains sparse, and the underlying genetic basis is unknown. Findings from an ongoing study in this internationally significant area are reported here.Methods Aedes aegypti collected from each city were raised to adults and assayed for resistance to permethrin, deltamethrin (with and without the synergist piperonyl butoxide, PBO), fenitrothion, and bendiocarb. Two fragments of the voltage-gated sodium channel (Vgsc), encompassing four previously identified mutation sites, were sequenced and subsequently genotyped to determine associations with resistance. Expression of five candidate genes (CYP9J10, CYP9J28, CYP9J32, CYP9M6, ABCB4) previously associated with pyrethroid resistance was compared between assay survivors and controls.ResultsJeddah and Makkah populations exhibited resistance to multiple insecticides and a similarly high prevalence of resistance to deltamethrin compared to a resistant Cayman strain, with a significant influence of age and exposure duration on survival. PBO pre-exposure increased pyrethroid mortality significantly in the Jeddah, but not the Makkah strain. Three potentially interacting Vgsc mutations were detected: V1016G and S989P were in perfect linkage disequilibrium in each strain and strongly predicted survival, especially in the Makkah strain, but were in negative linkage disequilibrium with 1534C, though some females with the Vgsc triple mutation were detected. The candidate gene CYP9J28 was significantly over-expressed in Jeddah compared to two susceptible reference strains, but none of the candidate genes was consistently up-regulated to a significant level in the Makkah strain.ConclusionsDespite their proximity, Makkah and Jeddah exhibit significant differences in pyrethroid resistance phenotypes, with some evidence to suggest a different balance of mechanisms, for example with more impact associated with CYP450s in the Jeddah strain, and the dual kdr mutations 989P and 1016G in the more resistant Makkah strain. The results overall demonstrate a major role for paired target site mutations in pyrethroid resistance and highlight their utility for diagnostic monitoring.Electronic supplementary materialThe online version of this article (doi:10.1186/s13071-017-2096-6) contains supplementary material, which is available to authorized users.

Co‐occurrence of V1016I and F1534C mutations in the voltage‐gated sodium channel and resistance to pyrethroids in Aedes aegypti (L.) from the Colombian Caribbean region

“…In Asia, V1016G has been found with S989P in Thailand and Malaysia, V1016G and F1534C in Singapore, S989P, V1016G and F1534C in China, Thailand, Myanmar, Saudi Arabia and Indonesia, and T1520I with F1534C in India. 14,15,[29][30][31][32][33][34] In the Americas, the co-occurrence of V1016I and F1534C has been found in the Caribbean Islands, Mexico, Brazil, Venezuela and the USA; in Africa, the co-occurrence of V1016I and F1534C in Ghana has been reported. 31,[35][36][37][38][39][40][41] In conclusion, we report here the co-occurrence of mutations V1016I and F1534C in populations of A. aegypti of the Colombian Caribbean region with variation in its allelic and genotypic frequencies.…”

Heterogeneous genetic invasions of three insecticide resistance mutations in Indo-Pacific populations ofAedes aegypti(L.)

“…aegypti collected from Saudi Arabia have been identified as being triple mutant heterozygotes with all three mutations on the same chromosome (unlike the combination of our haplotypes H1 and H2, Fig. 2a) and these individuals were susceptible to deltamethrin (Al Nazawi, Aqili, Alzahrani, McCall, & Weetman, 2017).…”

The need to harmonize insecticide resistance testing: methodology, intensity concentrations and molecular mechanisms evaluated inAedes aegyptipopulations in Central America and Hispaniola

“…The fact that most of individuals are heterozygous for F1534C seems to indicate that its presence is not associated with resistance - although the theory that it is contributing to resistance in association with other mutations cannot be discarded. Other mutations such as G923V, (reported in the Americas (29, 57, 84, 86, 93)) and S989P, have been reported to be associated with resistance when in combination with other mutations (98, 99, 104), were not screened in this study but should be considered for future work.…”