Department of Medical Entomology and Vector Control, School of Medicine, Zanjan University of Medical Sciences, Zanjan, Iran.
Parasit Vectors. 2020 Sep 23;13(1):485. doi: 10.1186/s13071-020-04364-z.
The head louse, Pediculus humanus capitis, is the most important ectoparasite causing many health problems. Several linkages are presented for this parasite, each representing a particular geographical distribution, prevalence rate, vector competence, susceptibility to pediculicides, and infestation rate. Determining the genetic nature of these linkages is necessary to identify the population structure and also to develop and monitor control programmes against head lice. This study was designed to analyse cox1 and cytb genes and determine the mitochondrial clades in head lice populations in the northwest of Iran.
Adult head lice were collected from infested females of Ardabil, East and West Azerbaijan, and Zanjan Provinces from 2016 to 2018. Partial fragments of the mitochondrial genes cox1 and cytb were amplified by PCR and some of the amplicons were sequenced. All confirmed sequences were analysed, and the frequency of each mitochondrial clade was determined in the studied areas.
A total of 6410 females were clinically examined, and 897 adult head lice were collected from 562 infested cases. Genomic DNA was extracted from 417 samples, and fragments of cox1 and cytb genes were amplified in 348 individuals. Analysis of the 116 sequences showed the 632-bp and 495-bp fragments for cox1 and cytb genes, respectively. The nucleotide and haplotype diversities of cytb and cox1 genes were 0.02261 and 0.589 and 0.01443 and 0.424, respectively. Sequence analysis indicated 6 haplotypes clustered in two clades, A and B. The relative prevalence of clade B was 73% for cytb and 82% for cox1 gene. Haplotypes of clade B were found in all the studied areas, while those of clade A were observed only in rural and suburban areas.
To our knowledge, this is the first study investigated deeply the field populations of Pediculus and documented two clades in the Middle East. The considerable prevalence of pediculosis in the studied areas requires authorities' attention to establish effective control and preventive measures. Given the role of cytb in monitoring population groups, application of this marker is suggested for future epigenetic studies to evaluate the factors affecting the abundance of these clades.
人头虱，Pediculus humanus capitis，是引起许多健康问题的最重要的外寄生虫之一。该寄生虫有几个联系，每个联系代表着特定的地理分布、流行率、媒介能力、对杀虱剂的敏感性和感染率。确定这些联系的遗传性质对于确定人口结构以及开发和监测针对头虱的控制计划是必要的。本研究旨在分析 cox1 和 cytb 基因，并确定伊朗西北部头虱种群的线粒体支系。
从 2016 年至 2018 年，从来自东阿塞拜疆、西阿塞拜疆和赞詹省的受感染女性中采集成年头虱。通过 PCR 扩增线粒体基因 cox1 和 cytb 的部分片段，并对一些扩增子进行测序。分析所有确认的序列，并确定研究区域中每个线粒体支系的频率。
共对 6410 名女性进行了临床检查，从 562 例感染病例中采集了 897 只成年头虱。从 417 个样本中提取基因组 DNA，从 348 个人中扩增了 cox1 和 cytb 基因片段。对 116 个序列的分析显示，cox1 和 cytb 基因分别为 632-bp 和 495-bp 片段。cytb 和 cox1 基因的核苷酸和单倍型多样性分别为 0.02261 和 0.589 以及 0.01443 和 0.424。序列分析表明，6 个单倍型聚类为两个支系，A 和 B。cytb 基因的分支 B 的相对流行率为 73%，cox1 基因的相对流行率为 82%。分支 B 的单倍型在所有研究区域均有发现，而分支 A 的单倍型仅在农村和郊区地区发现。
据我们所知，这是首次深入研究中东地区的人头虱实地种群，并记录了两个支系。在研究区域中，头虱病的高发病率需要当局注意，以建立有效的控制和预防措施。鉴于 cytb 在监测种群方面的作用，建议在未来的表观遗传研究中应用该标记，以评估影响这些支系丰度的因素。
