Department of Helminthology, Faculty of Tropical Medicine, Mahidol University, Bangkok, 10400, Thailand.
Vector Biology and Control Section, Department of Entomology, Armed Forces Research Institute of Medical Sciences (AFRIMS), Bangkok, 10400, Thailand.
Parasit Vectors. 2021 Jul 3;14(1):352. doi: 10.1186/s13071-021-04856-6.
Phlebotomine sand flies are vectors of Leishmania spp. At least 27 species of sand flies have been recorded in Thailand. Although human leishmaniasis cases in Thailand are mainly imported, autochthonous leishmaniasis has been increasingly reported in several regions of the country since 1999. Few studies have detected Leishmania infection in wild-caught sand flies, although these studies were carried out only in those areas reporting human leishmaniasis cases. The aim of this study was therefore to identity sand fly species and to investigate Leishmania infection across six provinces of Thailand.
Species of wild-caught sand flies were initially identified based on morphological characters. However, problems identifying cryptic species complexes necessitated molecular identification using DNA barcoding in parallel with identification based on morphological characters. The wild-caught sand flies were pooled and the DNA isolated prior to the detection of Leishmania infection by a TaqMan real-time PCR assay.
A total of 4498 sand flies (1158 males and 3340 females) were caught by trapping in six provinces in four regions of Thailand. The sand flies were morphologically classified into eight species belonging to three genera (Sergentomyia, Phlebotomus and Idiophlebotomus). Sergentomyia iyengari was found at all collection sites and was the dominant species at most of these, followed in frequency by Sergentomyia barraudi and Phlebotomus stantoni, respectively. DNA barcodes generated from 68 sand flies allowed sorting into 14 distinct species with 25 operational taxonomic units, indicating a higher diversity (by 75%) than that based on morphological identification. Twelve barcoding sequences could not be assigned to any species for which cytochrome c oxidase subunit I sequences are available. All tested sand flies were negative for Leishmania DNA.
Our results confirm the presence of several sand fly species in different provinces of Thailand, highlighting the importance of using DNA barcoding as a tool to study sand fly species diversity. While all female sand flies tested in this study were negative for Leishmania, the circulation of Leishmania spp. in the investigated areas cannot be ruled out.
白蛉是利什曼原虫的传播媒介。在泰国，至少有 27 种白蛉被记录。尽管泰国的人类利什曼病病例主要是输入性的，但自 1999 年以来，该国几个地区的本土利什曼病病例报道越来越多。尽管这些研究仅在报告人类利什曼病病例的地区进行，但很少有研究检测到野生捕获的白蛉中的利什曼原虫感染。因此，本研究的目的是鉴定白蛉种类，并调查泰国六个省的利什曼原虫感染情况。
根据形态特征初步鉴定野生捕获白蛉的种类。然而，由于难以识别隐种复合体，因此需要使用 DNA 条形码与形态特征鉴定同时进行分子鉴定。在通过 TaqMan 实时 PCR 检测检测到利什曼原虫感染之前，对捕获的野生白蛉进行了分组和 DNA 分离。
在泰国四个地区的六个省，通过诱捕共捕获了 4498 只白蛉（1158 只雄性和 3340 只雌性）。白蛉通过形态学分类为三个属（Sergeomyia、Phlebotomus 和 Idiophlebotomus）的 8 个种。在所有采集点都发现了 Sergeomyia iyengari，并且是大多数采集点的优势种，其次是 Sergentomyia barraudi 和 Phlebotomus stantoni。从 68 只白蛉中生成的 DNA 条形码可分为 14 个不同的种，有 25 个操作分类单元，表明多样性（高 75%）高于形态鉴定。12 个条形码序列无法分配到任何具有细胞色素 c 氧化酶亚基 I 序列的种。所有测试的白蛉均未检测到利什曼原虫 DNA。
我们的结果证实了泰国不同省份存在几种白蛉，这突出表明使用 DNA 条形码作为研究白蛉物种多样性的工具的重要性。虽然本研究中测试的所有雌性白蛉均未检测到利什曼原虫，但不能排除在调查地区存在利什曼原虫的循环。
