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Diversity and frequency of kdr mutations within Anopheles sinensis populations from Guangxi, China.

ABSTRACT: Anopheles sinensis is a major vector of malaria in China and its control is under great threat as the development of insecticide resistance. Voltage-gated sodium channel (VGSC) is the target of several classes of insecticides. Genetic mutations of VGSC have been documented to confer knockdown resistance (kdr) to dichlorodiphenyltrichloroethane (DDT) and pyrethroids in mosquitoes. To control this vector efficiently, it is important to know the resistance-associated genetic mutations, their distribution frequencies and genealogical relations.Three hundreds and thirteen (313) adults of An. sinensis collected from nine locations across Guangxi Zhuang Autonomous Region were used. The partial sequence of the An. sinensis voltage gated sodium channel gene (AS-VGSC) containing codon 1014 was sequenced. PHASE2.1 was used to construct the haplotypes of each individual, and the accuracy of haplotypes was further confirmed by clone sequencing. The genealogical relations of kdr mutations in AS-VGSC was analysed using TCS 2.1 and Network 5.0.Sixteen AS-VGSC haplotypes including seven haplotypes carrying non-synonymous mutations at codon 1014, and fifty-five AS-VGSC genotypes were identified from 313 mosquitoes collected from nine geographical locations across Guangxi. The number of haplotypes in each of the nine populations ranged from 5 to 13. The frequency of haplotypes carrying kdr mutations ranged from 2.7 to 80.0 % within the nine populations, of which 1014C was unexpectedly high in the northeast of Guangxi. Genealogical analysis suggested multiple origins of kdr mutations in An. sinensis.Diverse haplotypes of AS-VGSC are distributed in Guangxi. The presence of haplotypes carrying mutations at codon 1014 indicates a risk of pyrethroid and DDT resistance. The kdr mutations show differential distribution geographically, with high frequencies occurred in the northeast of Guangxi. Genealogical analysis suggests multiple origins of kdr mutations in An. sinensis populations in Guangxi. These findings have important practical implications for the sustainability of An. sinensis control programmes.

SUBMITTER: Yang C

PROVIDER: S-EPMC4986192 | biostudies-literature | 2016 Aug

REPOSITORIES: biostudies-literature

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Diversity and frequency of kdr mutations within Anopheles sinensis populations from Guangxi, China.

Yang Chan C Feng Xiangyang X Huang Zushi Z Li Mei M Qiu Xinghui X

Malaria journal 20160815 1

<h4>Background</h4>Anopheles sinensis is a major vector of malaria in China and its control is under great threat as the development of insecticide resistance. Voltage-gated sodium channel (VGSC) is the target of several classes of insecticides. Genetic mutations of VGSC have been documented to confer knockdown resistance (kdr) to dichlorodiphenyltrichloroethane (DDT) and pyrethroids in mosquitoes. To control this vector efficiently, it is important to know the resistance-associated genetic muta ...[more]

PMID: 27527509

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Project description:BACKGROUND:In South Asia, the epidemiology of malaria is complex, and transmission mainly occurs in remote areas near international borders. Vector control has been implemented as a key strategy in malaria prevention for decades. A rising threat to the efficacy of vector control efforts is the development of insecticide resistance, thus it is important to monitor the type and frequency of insecticide resistant alleles in the disease vectors such as An. sinensis along the China-Vietnam border. Such information is needed to synthesize effective malaria vector control strategies. METHODS:A total of 208 adults of An. sinensis, collected from seven sites in southwest Guangxi along the China-Vietnam border, were inspected for the resistance-conferring G119S mutation in acetylcholinesterase (AChE) by PCR-RFLP (polymerase chain reaction restriction fragment length polymorphism) and kdr mutations in the voltage-gated sodium channel (VGSC) by sequencing. In addition, the evolutionary origin of An. sinensis vgsc gene haplotypes was analyzed using Network 5.0. RESULTS:The frequencies of mutant 119S of AChE were between 0.61-0.85 in the seven An. sinensis populations. No susceptible homozygote (119GG) was detected in three of the seven sites (DXEC, LZSK and FCGDX). Very low frequencies of kdr (0.00-0.01) were detected in the seven populations, with most individuals being susceptible homozygote (1014LL). The 1014F mutation was detected only in the southeast part (FCGDX) at a low frequency of 0.03. The 1014S mutation was distributed in six of the seven populations with frequencies ranging from 0.04 to 0.08, but absent in JXXW. Diverse haplotypes of 1014L and 1014S were found in An. sinensis along the China-Vietnam border, while only one 1014F haplotype was detected in this study. Consistent with a previous report, resistant 1014S haplotypes did not have a single origin. CONCLUSIONS:The G119S mutation of AChE was present at high frequencies (0.61-0.85) in the An. sinensis populations along the China-Vietnam border, suggesting that the vector control authorities should be cautious when considering carbamates and organophosphates as chemicals for vector control. The low frequencies (0.00-0.11) of kdr in these populations suggest that pyrethroids remain suitable for use against An. sinensis in these regions.

Project description:BACKGROUND:Malaria is a deadly vector-borne disease in tropical and subtropical regions. Although indigenous malaria has been eliminated in Guangxi of China, 473 confirmed cases were reported in the Northern region of neighbouring Vietnam in 2014. Considering that frequent population movement occurs across the China-Vietnam border and insecticide resistance is a major obstacle in disease vector control, there is a need to know the genotype and frequency of insecticide resistance alleles in Anopheles sinensis populations along the China-Vietnam border and to take action to prevent the possible migration of insecticide resistance alleles across the border. METHODS:Two hundred and eight adults of An. sinensis collected from seven locations in Guangxi along the China-Vietnam border were used in the investigation of individual genotypes of the AsRDL gene, which encodes the RDL gamma-aminobutyric acid (GABA) receptor subunit in An. sinensis. PCR-RFLP (polymerase chain reaction-restriction fragment length polymorphism) analysis was deployed to genotype codon 345, while direct sequencing of PCR products was conducted to clarify the genotypes for codons 296 and 327 of the AsRDL gene. The genealogical relation of AsRDL haplotypes was analyzed using Network 5.0. RESULTS:Three putative insecticide resistance related mutations (A296S, V327I and T345S) were detected in all the seven populations of An. sinensis in Guangxi along the China-Vietnam border. The resistance-conferring A296S mutation was found to be widely distributed and present at notably high frequencies (78.8% to 100%). Relatively lower frequencies of mutations V327I (26.9% to 53.2%) and T345S (0% to 28.8%) were observed. The V327I or T345S always occurred in the presence of A296S. Evolutionary analysis of 21 AsRDL haplotypes indicated multiple origins of the A296S and V327I mutations. CONCLUSION:The resistance A296S allele was present at high frequencies in the An. sinensis populations along the China-Vietnam border, indicating a risk of resistance to insecticides targeting RDL. The double mutations (A296S?+?V327I) may have evolved from alleles carrying the A296S mutation by scaffolding the additional mutation V327I, and A296S allele may have multiple evolutionary origins. These findings will help inform strategies for vector control and malaria prevention.

Project description:Anopheles sinensis is a major vector of malaria in China. The gamma-aminobutyric acid (GABA)-gated chloride channel, encoded by the RDL (Resistant to dieldrin) gene, is the important target for insecticides of widely varied structures. The use of various insecticides in agriculture and vector control has inevitably led to the development of insecticide resistance, which may reduce the control effectiveness. Therefore, it is important to investigate the presence and distribution frequency of the resistance related mutation(s) in An. sinensis RDL to predict resistance to both the withdrawn cyclodienes (e.g. dieldrin) and currently used insecticides, such as fipronil.Two hundred and forty adults of An. sinensis collected from nine locations across Guangxi Zhuang Autonomous Region were used. Two fragments of An. sinensis RDL (AsRDL) gene, covering the putative insecticide resistance related sites, were sequenced respectively. The haplotypes of each individual were reconstructed by the PHASE2.1 software, and confirmed by clone sequencing. The phylogenetic tree was built using maximum-likelihood and Bayesian inference methods. Genealogical relations among different haplotypes were also analysed using Network 5.0.The coding region of AsRDL gene was 1674 bp long, encoding a protein of 557 amino acids. AsRDL had 98.0% amino acid identity to that from Anopheles funestus, and shared common structural features of Cys-loop ligand-gated ion channels. Three resistance-related amino acid substitutions (A296S, V327I and T345S) were detected in all the nine populations of An. sinensis in Guangxi, with the 296S mutation being the most abundant (77-100%), followed by 345S (22-47%) and 327I (8-60%). 38 AsRDL haplotypes were identified from 240 individuals at frequencies ranging from 0.2 to 34.8%. Genealogical analysis suggested multiple origins of the 345S mutation in AsRDL.The near fixation of the 296S mutation and the occurrence of the 327I and 345S mutations in addition to 296S, in all the nine tested An. sinensis populations in Guangxi, strongly indicate a risk of multiple insecticide resistance. The haplotype diversity plus genetic heterogeneities in the geographical distribution, and multiple origins of AsRDL alleles call for a location-customized strategy for monitoring and management of insecticide resistance.

Project description:BackgroundAedes albopictus (Skuse) is an important vector of chikungunya, dengue, yellow fever and Zika viruses. In the absence of anti-viral medication and with limited availability of a commercial vaccine for public health use, vector control remains an effective means for reducing Aedes-borne disease morbidity. Knowledge about genetic mutations associated with insecticide resistance (IR) is a prerequisite for developing rapid resistance diagnosis, and the distribution and frequency of IR conferring mutations is important information for making smart vector control decisions.MethodsPartial DNA sequences of domain II and domain III of Ae. albopictus voltage gated sodium channel (VGSC) gene were amplified from a total of 426 individuals, collected from 17 sites in the Beijing municipality. These DNA fragments were sequenced to discover the possible genetic mutations mediating knockdown resistance (kdr) to pyrethroids. The frequency and distribution of kdr mutations were assessed in the 17 Ae. albopictus populations. The origin of kdr mutations was investigated by haplotype clarification and phylogenetic analysis.ResultsSequence alignments revealed the existence of multiple mutations (V1016G, I1532T, F1534S and F1534L) in VGSC. The highest frequency of the mutant 1016G allele (0.647) was found in Haidian, while 1016G was not detected in Huai Rou, Yan Qing, Ping Gu and Shun Yi. The frequency of 1532T was highest (0.537) in the population from the Olympic Forest Park (OFP, Chao Yang District), but not detectable in Huai Rou and Mi Yun. Two mutations were observed at codon 1534 with different distribution patterns: 1534L was only found in Tong Zhou (TZ) with a frequency of 0.017, while 1534S was distributed in TZ, OFP, Fang Shan, Da Xing and Shi Jing Shan with frequencies ranging from 0.019 (OFP) to 0.276 (TZ). One 1016G, one 1532T, one 1534L and two 1534S haplotypes were identified.ConclusionsMultiple mutations (V1016G, I1532T, F1534L/S) in VGSC were found in Ae. albopictus in Beijing. This represents the first report of V1016G in Ae. albopictus. Sequence alignment and phylogenetic analysis revealed multiple origins of 1534S. The spatial heterogeneity in distribution and frequency of kdr mutations calls for a site-specific strategy for the monitoring of insecticide resistance. The relatively high frequencies of V1016G warn of a risk of pyrethroid resistance in mosquitoes in the urban zones.

Project description:BackgroundVector control is still a pivotal method for preventing malaria, and its potency is weakened by the increasing resistance of vectors to chemical insecticides. As the most abundant and vital malaria vector in Southeast Asia, the chemical insecticide resistance status in Anopheles sinensis remains elusive in Laos, which makes it imperative to evaluate the true nature of chemical insecticide resistance-associated genetic mutations in An. sinensis in Laos.MethodsAdult An. sinensis were collected from three border regions in Laos. DNA was extracted from individual mosquitoes. PCR amplification and DNA sequencing of a fragment containing codon 1014 of the voltage-gated sodium channel (vgsc) gene were completed to study the kdr allele frequency distribution, kdr intron polymorphism, population genetic diversity, and the evolutionary status of the kdr codon. The mitochondrial cytochrome c oxidase subunit II gene (COII) was amplified and sequenced to examine population variations, genetic differentiation, spatial population structure, population expansion, and gene flow patterns.ResultsNine wild kdr haplotypes of the vgsc gene were detected in this study, and eight of them, namely 1014L1, 1014L2, 1014L4, 1014L7, 1014L9, 1014L10, 1014L11, and 1014L21, were discovered in the China-Laos border (northern Laos), while 1014L3 was only detected in the Thailand-Laos border (northwestern Laos) and Cambodia-Laos border (southern Laos). The newly identified haplotype, 1014L21, was uniquely distributed in the China-Laos border and was not identified in other countries. Based on sequence analysis of the mitochondrial COII genes, significant genetic differentiation and limited gene flow were detected between the China-Laos and Cambodia-Laos An. sinensis populations, which suggested that those two regions were genetically isolated. The distinct distribution of the kdr haplotype frequencies is probably the result of geographical isolation in mosquito populations.ConclusionsLack of kdr mutations in the vgsc gene was probably due to genetic isolation and the absence of intense selection pressure in the three border regions of Laos. This study reveals that pyrethroid-based chemical insecticides are still appropriate for battling An. sinensis in parts of Laos, and routine monitoring of chemical insecticide resistance should be continuously implemented and focused on more restricted areas as part of chemical insecticide resistance management.

Project description:BackgroundAedes albopictus is the primary vector of dengue fever in China. This mosquito species has a wide distribution range in China and can be found in the tropical climate zones of southern provinces through to temperate climate zones of northern provinces. Insecticides are an important control method, especially during outbreaks of dengue fever, but increasing insecticide resistance raises the risk of failure to control vector-borne diseases. Knockdown resistance (kdr) caused by point mutations in the voltage-gated sodium channel (VGSC) gene is a key mechanism that confers resistance to pyrethroids. In this study we explored the characteristics and possible evolutionary trend of kdr mutation in Ae. albopictus based on analysis of the kdr mutations in field populations of mosquitoes in China.MethodsA total of 1549 adult Ae. albopictus were collected from 18 sites in China from 2017 to 2019 and 50 individuals from three sites in the 1990s. A fragment of approximately 350 bp from part of the S6 segment in the VGSC gene domain III was amplified and sequenced. Using TCS software version 1.21A, we constructed haplotypes of the VGSC gene network and calculated outgroup probability of the haplotypes. Data of annual average temperatures (AAT) of the collection sites were acquired from the national database. The correlation between AAT of the collection site and the kdr mutation rate was analyzed by Pearson correlation using SPSS software version 21.0.ResultsThe overall frequency of mutant allele F1534 was 45.6%. Nine mutant alleles were detected at codon 1534 in 15 field populations, namely TCC/TCG (S) (38.9%), TTG/CTG/CTC/TTA (L) (3.7%), TGC (C) (2.9%), CGC (R) (0.3%) and TGG (W) (0.1%). Only one mutant allele, ACC (T), was found at codon 1532, with a frequency of 6.4% in ten field populations. Moreover, multiple mutations at alleles I1532 and F1534 in a sample appeared in five populations. The 1534 mutation rate was significantly positively related to AAT (Pearson correlation: r(18) = 0.624, P = 0.0056), while the 1532 mutation rate was significantly negatively related to AAT (Pearson correlation: r(18) = - 0.645, P = 0.0038). Thirteen haplotypes were inferred, in which six mutant haplotypes were formed by one step, and one additional mutation formed the other six haplotypes. In the samples from the 1990s, no mutant allele was detected at codon 1532 of the VGSC gene. However, F1534S/TCC was found in HNHK94 with an unexpected frequency of 100%.ConclusionsKdr mutations are widespread in the field populations of Ae. albopictus in China. Two novel mutant alleles, F1534W/TGG and F1534R/CGC, were detected in this study. The 1534 kdr mutation appeared in the population of Ae. albopictus no later than the 1990s. The F1534 mutation rate was positively correlated with AAT, while the I1532 mutation rate was negatively correlated with AAT. These results indicate that iInsecticide usage should be carefully managed to slow down the spread of highly resistant Ae. albopictus populations, especially in the areas with higher AAT.

Project description:BackgroundVivax malaria was historically epidemic in Henan Province of China and Anopheles sinensis was the main vectors and poor farming communities bare the greatest burden of disease. Knockdown resistance in An. sinensis is one of the mechanisms of resistance against pyrethroids. In the present study, the frequency of mutations from An. sinensis was examined in Henan province, China.MethodsAnopheles was collected from Kaifeng, Tongbai, Tanghe, Pingqiao, Shihe, and Yongcheng counties of Henan province in 2013. Molecular identification of Anopheles species was conducted by polymerase chain reaction (PCR) amplifying the internal transcribed spacer 2 (ITS2). Part of the IIS6 domain of the para-type sodium channel protein gene was polymerase chain reaction-amplified and directly sequenced. Frequency and geographic difference of kdr gene mutant types were analysed.Results208 Anopheles were received molecular identification, of which 169 (81.25%) were An. sinensis, 25 (12.02%) were Anopheles yatsushiroensis, and 12 (5.77%) were Anopheles lesteri. A 325 bp fragment of the para-type sodium channel gene including position 1014 was successfully sequenced from 139 Anopheles, of which 125 (89.93%) were An. sinensis, 12 (8.63%) were An. yatsushiroensis, 2 (1.44%) were An. lesteri. The molecular analyses revealed that mutations existed at codon 1014 in An. sinensis but not in An. yatsushiroensis and An. lesteri. Frequency of kdr mutation was 73.60% (92/125) from population of An. sinensis in Henan province, of which L1014F (TTT + TTC) allele frequencies accounted for 46.40% (58/125), and was higher than that of L1014C(TGT) which accounted for 27.20% (34/125) ( χ2 = 55.423, P < 0.001). The frequency of kdr mutation in Kaifeng county was 100% (49/49), and was higher than that of 37.93% (11/29) in Tongbai, 54.55% (6/11) in Pingqiao, 50.00% (3/3) in Shihe, and 62.50% (10/16) in Yongcheng county, respectively (χ2 = 39.538, P < 0.001; χ2 = 24.298, P < 0.001; χ2 = 25.913, P < 0.001; χ2 = 20.244, P < 0.001). While 92.86% (13/14) frequency of kdr mutation was found in Tanghe county, which was higher than that in Tongbai county (χ2 = 11.550, P = 0.0018).ConclusionsA high frequency of kdr gene mutations from population of An. sinensis in Henan province was found.

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Diversity and frequency of kdr mutations within Anopheles sinensis populations from Guangxi, China.

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Diversity and frequency of kdr mutations within Anopheles sinensis populations from Guangxi, China.

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