title: Knockdown resistance of Anopheles sinensis in Henan province, China.
abstract: BACKGROUND
  Vivax 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.
  
  
  METHODS
  Anopheles 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.
  
  
  RESULTS
  208 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).
  
  
  CONCLUSIONS
  A high frequency of kdr gene mutations from population of An. sinensis in Henan province was found.
authors.affiliation: Department of Parasite Disease Control and Prevention, Henan Center for Disease Control and Prevention, Zhengzhou, 450016, P. R. China. Zhwei69@163.com.
authors.forename: Hong-wei
authors.initials: HW
authors.lastname: Zhang
authors.affiliation: Department of Parasite Disease Control and Prevention, Henan Center for Disease Control and Prevention, Zhengzhou, 450016, P. R. China. 14872209@qq.com.
authors.forename: Ying
authors.initials: Y
authors.lastname: Liu
authors.affiliation: School of Medicine and Health Management, Tongji Medical College, Huazhong University of Science & Technology, Wuhan, Hubei, 430030, P. R. China. walnut1221@163.com.
authors.forename: Tao
authors.initials: T
authors.lastname: Hu
authors.affiliation: Department of Parasite Disease Control and Prevention, Henan Center for Disease Control and Prevention, Zhengzhou, 450016, P. R. China. zrm920@126.com.
authors.forename: Rui-min
authors.initials: RM
authors.lastname: Zhou
authors.affiliation: Department of Parasite Disease Control and Prevention, Henan Center for Disease Control and Prevention, Zhengzhou, 450016, P. R. China. chenjs@hncdc.com.cn.
authors.forename: Jian-she
authors.initials: JS
authors.lastname: Chen
authors.affiliation: Department of Parasite Disease Control and Prevention, Henan Center for Disease Control and Prevention, Zhengzhou, 450016, P. R. China. qianyangdan1983@163.com.
authors.forename: Dan
authors.initials: D
authors.lastname: Qian
authors.affiliation: Department of Parasite Disease Control and Prevention, Henan Center for Disease Control and Prevention, Zhengzhou, 450016, P. R. China. tochyun@163.com.
authors.forename: Cheng-yun
authors.initials: CY
authors.lastname: Yang
authors.affiliation: Department of Parasite Disease Control and Prevention, Henan Center for Disease Control and Prevention, Zhengzhou, 450016, P. R. China. 819482937@qq.com.
authors.forename: Yu-ling
authors.initials: YL
authors.lastname: Zhao
authors.affiliation: Department of Parasite Disease Control and Prevention, Henan Center for Disease Control and Prevention, Zhengzhou, 450016, P. R. China. lsh0427@163.com.
authors.forename: Su-hua
authors.initials: SH
authors.lastname: Li
authors.affiliation: Department of Parasitology, Medical College, Zhengzhou University, Zhengzhou, 450052, P. R. China. cuij@zzu.edu.cn.
authors.forename: Jing
authors.initials: J
authors.lastname: Cui
authors.affiliation: Department of Parasitology, Medical College, Zhengzhou University, Zhengzhou, 450052, P. R. China. wangzq@zzu.edu.cn.
authors.forename: Zhong-quan
authors.initials: ZQ
authors.lastname: Wang
authors.affiliation: School of Medicine and Health Management, Tongji Medical College, Huazhong University of Science & Technology, Wuhan, Hubei, 430030, P. R. China. zcfeng@mail.tjmu.edu.cn.
authors.forename: Zhanchun
authors.initials: Z
authors.lastname: Feng
authors.affiliation: Department of Parasite Disease Control and Prevention, Henan Center for Disease Control and Prevention, Zhengzhou, 450016, P. R. China. Bianlixu@163.com.
authors.forename: Bian-li
authors.initials: BL
authors.lastname: Xu
mesh_terms: D000818:Animals; D000852:Anopheles / Q000187:drug effects* / Q000235:genetics / Q000502:physiology*; D002681:China; D021903:DNA, Ribosomal Spacer / Q000737:chemistry / Q000235:genetics; D005787:Gene Frequency; D005843:Geography; D007303:Insect Vectors / Q000187:drug effects* / Q000235:genetics / Q000502:physiology*; D007305:Insecticide Resistance; D007306:Insecticides / Q000494:pharmacology*; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D011722:Pyrethrins / Q000494:pharmacology*; D017422:Sequence Analysis, DNA; D015222:Sodium Channels / Q000235:genetics
chemical_list: D021903:DNA, Ribosomal Spacer; D007306:Insecticides; D011722:Pyrethrins; D015222:Sodium Channels