Aguirre-Obando Oscar Alexander, Martins Ademir Jesus, Navarro-Silva Mário Antônio
Laboratório de Entomologia Médica e Veterinária, Setor de Ciências Biológicas, Departamento de Zoologia, Universidade Federal do Paraná, PO Box 19020, Curitiba, 81531-980, Paraná, Brazil.
Laboratório de Fisiologia e Controle de Artrópodes Vetores, Instituto Oswaldo Cruz-FIOCRUZ, Av. Brasil 4365, Rio de Janeiro-RJ, PO Box 2104-900, Brazil.
Parasit Vectors. 2017 Mar 27;10(1):160. doi: 10.1186/s13071-017-2089-5.
Knockdown resistance (kdr), caused by alterations in the voltage-gated sodium channel (Na), is one of the mechanisms responsible for pyrethroid (PY) resistance. In the Asian tiger mosquito, Aedes albopictus, at least four different mutations were described in the IIIS6 Na segment in populations from Asia, North America and Europe. In contrast, in Aedes aegypti at least 12 non-synonymous mutations have been reported at nine different codons, mostly in the IIS6 and IIIS6 Na segments. The Phe1534Cys kdr mutation in the IIIS6 Na segment is the most prevalent in populations of Ae. aegypti worldwide, also found in Ae. albopictus from Singapore. Herein, we investigated the DNA diversity corresponding to the IIS6 and IIIS6 Na segments in natural populations of Ae. albopictus from Brazil.
DNA from eight Brazilian Ae. albopictus natural populations were individually extracted and pooled by states of origin, amplified, cloned and sequenced for the corresponding IIS6 and IIIS6 Na segments. Additionally, samples from each location were individually genotyped by an allelic specific PCR (AS-PCR) approach to obtain the genotypic and allelic frequencies for the 1534 Na site.
No non-synonymous substitutions were observed in the IIS6 sequences. However, the Phe1534Cys kdr mutation was evidenced in the Ae. albopictus Na IIIS6 segment sequences from Paraná (PR) and Rondônia (RO) states, but not from Mato Grosso (MT) state. The 1534Cys allele varied from 3% (Marilena/PR and Porto Velho/RO) to 10% (Foz do Iguaçu/PR). To our knowledge, this paper reports the first occurrence and provides distribution data of a possible kdr mutation in Ae. albopictus in South America.
The emergence of a likely kdr mutation in Ae. albopitus natural populations is a signal of alert for vector control measures since PY are the most popular insecticides adopted by residents. Additionally, once the kdr allele is present, its frequency tends to increase faster under exposition to those compounds. Although the Asian tiger mosquito is not incriminated as an important vector of dengue, chikungunya and Zika viruses in South America, its importance in this regard has been extensively discussed since Ae. albopictus is rapidly spreading and can also migrate between sylvatic and urban environments. Therefore, insecticide resistance monitoring initiatives should also be extended to Ae. albopictus in Brazil in order to maintain chemical compounds as an efficient vector control tool when needed.
击倒抗性（kdr）由电压门控钠通道（Na）的改变引起，是拟除虫菊酯（PY）抗性的机制之一。在白纹伊蚊中，亚洲、北美和欧洲种群的IIIS6 Na片段中描述了至少四种不同的突变。相比之下，在埃及伊蚊中，九个不同密码子处至少报告了12个非同义突变，大多位于IIS6和IIIS6 Na片段。IIIS6 Na片段中的Phe1534Cys kdr突变在全球埃及伊蚊种群中最为普遍，在新加坡的白纹伊蚊中也有发现。在此，我们调查了巴西白纹伊蚊自然种群中与IIS6和IIIS6 Na片段对应的DNA多样性。
从巴西八个白纹伊蚊自然种群中分别提取DNA，并按产地州进行合并，对相应的IIS6和IIIS6 Na片段进行扩增、克隆和测序。此外，通过等位基因特异性PCR（AS-PCR）方法对每个地点的样本进行个体基因分型，以获得1534 Na位点的基因型和等位基因频率。
在IIS6序列中未观察到非同义替换。然而，在巴拉那州（PR）和朗多尼亚州（RO）的白纹伊蚊Na IIIS6片段序列中发现了Phe1534Cys kdr突变，但在马托格罗索州（MT）未发现。1534Cys等位基因的比例从3%（玛丽莱娜/PR和波多韦柳/RO）到10%（伊瓜苏港/PR）不等。据我们所知，本文首次报道了南美白纹伊蚊中可能的kdr突变的出现并提供了分布数据。
白纹伊蚊自然种群中可能出现的kdr突变是一个警示信号，因为拟除虫菊酯是居民使用最广泛的杀虫剂，对病媒控制措施有影响。此外，一旦存在kdr等位基因，在接触这些化合物时其频率往往会更快增加。虽然在南美白纹伊蚊未被认定为登革热、基孔肯雅热和寨卡病毒的重要病媒，但由于白纹伊蚊正在迅速传播且可在野生和城市环境之间迁移，其在这方面的重要性已得到广泛讨论。因此，巴西的杀虫剂抗性监测计划也应扩展到白纹伊蚊，以便在需要时将化学药剂作为有效的病媒控制工具。
