Abstract
BackgroundAedes aegypti is a primary vector of dengue, chikungunya and Zika infections in India. In the absence of specific drugs or safe and effective vaccines for these infections, their control relies mainly on vector control measures. The emergence of insecticide resistance in vectors, especially against pyrethroids, is a serious threat to the insecticide-based vector control programme. This study reports the presence of multiple knockdown resistance (kdr) mutations present in an Ae. aegypti population from Bengaluru (India), including a new mutation F1534L.MethodsAedes aegypti collected from Bengaluru were subjected to insecticide susceptibility tests with DDT, deltamethrin and permethrin. The DNA sequencing of partial domain II, III and IV of the voltage-gated sodium channel (VGSC) was performed to screen kdr mutations present in the population and PCR-based assays were developed for their detection. Genotyping of kdr mutations was done using PCR-based assays, allelic frequencies were determined, and tests of genetic association of kdr mutations with the insecticide resistance phenotype were performed.ResultsThe Ae. aegypti population was resistant to DDT, deltamethrin and permethrin. The DNA sequencing of the VGSC revealed the presence of four kdr mutations, i.e. S989P and V1016G in domain II and two alternative kdr mutations F1534C and F1534L in domain III. Allele-specific PCR assays (ASPCR) were developed for the detection of kdr mutations S989P and V1016G and an existing PCR-RFLP based strategy was modified for the genotyping of all three known kdr mutations in domain III (F1534L, F1534C and T1520I). Genotyping of Ae. aegypti samples revealed a moderate frequency of S989P/V1016G (18.27%) and F1534L (17.48%), a relatively high frequency of F1534C (50.61%) and absence of T1520I in the population. Mutations S989P and V1016G were in complete linkage disequilibrium in this population while they were in linkage equilibrium with kdr mutations F1534C and F1534L. The alleles F1534C and F1534L are genetically associated with permethrin resistance.ConclusionsA new kdr mutation, F1534L, was found in an Ae. aegypti population from Bengaluru (India), co-occurring with the other three mutations S989P, V1016G and F1534C. The findings of a new mutation have implications for insecticide resistance management.
Highlights
Aedes aegypti is a primary vector of dengue, chikungunya and Zika infections in India
Identification of kdr mutations in Ae. aegypti population The DNA sequencing of partial domain II, III and IV of the voltage-gated sodium channel (VGSC) of the Ae. aegypti population collected from Bengaluru, India, revealed the presence of four mutations, i.e. S989P and V1016G in domain II, and F1534C and F1534L in domain III
In most of the cases, the identification of S989 and V1016 mutations were based on 1× sequencing data, where the forward sequence was used for identification of S989 alleles and the reverse sequence was used for V1016 alleles
Summary
Aedes aegypti is a primary vector of dengue, chikungunya and Zika infections in India. Aedes aegypti is a widely distributed mosquito species in tropical and subtropical regions and is a primary vector of several human arboviral infections mainly, dengue, chikungunya, yellow fever and Zika viruses. These arboviral infections are increasingly becoming a global health concern due to their rapid geographical spread and high disease burden [1]. In India, dengue and chikungunya are the main arboviral infections [4,5,6,7] with the recent introduction of the Zika virus (ZIKV) [8]. There had been an outbreak of Zika infections in Jaipur city [9], where Ae. aegypti has been incriminated as a Zika vector [10]
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