Center of Excellence in Vector Biology and Vector-Borne Disease, Faculty of Medicine, Chulalongkorn University, Bangkok 10330, Thailand; Department of Parasitology, Faculty of Medicine, Chulalongkorn University, Bangkok 10330, Thailand.
Center of Excellence in Vector Biology and Vector-Borne Disease, Faculty of Medicine, Chulalongkorn University, Bangkok 10330, Thailand.
Acta Trop. 2023 Aug;244:106949. doi: 10.1016/j.actatropica.2023.106949. Epub 2023 May 20.
Autochthonous leishmaniasis in Thailand has recently been a public health concern due to an increasing number of new clinical cases. Most indigenous cases were diagnosed with Leishmania (Mundinia) martiniquensis, and Leishmania (Mundinia) orientalis. However, some doubts regarding vector misidentification have arisen and need to be elucidated. Accordingly, we aimed to assess the species composition of sand flies and determine the molecular prevalence of trypanosomatids in the transmission area of leishmaniasis in southern Thailand. In the present study, a total of 569 sand flies were caught from the vicinity of a visceral leishmaniasis patient's house in Na Thawi District, Songkhla Province. Of these, 229 parous and gravid females consisted of Sergentomyia khawi, Se. barraudi, Phlebotomus stantoni, Grassomyia indica, and Se. hivernus, accounting for 31.4%, 30.6%, 29.7%, 7.9%, and 0.4%, respectively. However, Se. gemmea, which has previously been proposed as the most abundant species and putative vector of visceral leishmaniasis, was not found in the present study. Based on ITS1-PCR and sequence analysis, two specimens of Gr. indica and Ph. stantoni showed positive amplification of L. martiniquensis and L. donovani complex, respectively, the first one being presumed indigenous and the second one being not. Anuran Trypanosoma was also molecularly detected using SSU rRNA-PCR and ubiquitously found in 16 specimens of four dominant sand fly species except for Se. hivernus. The obtained sequences could be phylogenetically categorized into the two major amphibian clades (An04/Frog1 and An01+An02/Frog2). The existence of the monophyletic subgroup and distinct lineage suggests them as novel Trypanosoma species. The TCS network analysis of these anuran Trypanosoma sequences also revealed high haplotype diversity (Hd = 0.925 ± 0.050), but low nucleotide diversity (π = 0.019 ± 0.009). Furthermore, the living anuran trypanosomes were microscopically demonstrated in a single specimen of Gr. indica, supporting the vectorial capacity. Importantly, our data confirmed the scarcity of Se. gemmea and also uncovered, for the first time, the co-circulation of L. martiniquensis, L. donovani complex, and suspected novel anuran Trypanosoma spp. in phlebotomine sand files, implicating their potential role as vectors of trypanosomatid parasites. Therefore, the novel data from this study would greatly facilitate the comprehension of the complexity of trypanosomatid transmission and the establishment of prevention and control measures for this neglected disease more effectively.
在泰国，由于新的临床病例不断增加，土源性利什曼病最近成为了一个公共卫生关注点。大多数本地病例被诊断为曼氏利什曼原虫（Mundinia）和东方利什曼原虫（Mundinia）。然而，有关媒介物识别错误的一些疑问仍需澄清。因此，我们旨在评估南部泰国利什曼病传播区的沙蝇物种组成，并确定锥虫的分子流行率。
在本研究中，从 Songkhla 省那他威区一名内脏利什曼病患者的房屋附近共捕获了 569 只沙蝇。其中，229 只产卵和怀孕的雌蝇包括 Sergentomyia khawi、Se. barraudi、Phlebotomus stantoni、Grassomyia indica 和 Se. hivernus，分别占 31.4%、30.6%、29.7%、7.9%和 0.4%。然而，在本研究中未发现先前被提议为最丰富的物种和内脏利什曼病的可能媒介的 Se. gemmea。
基于 ITS1-PCR 和序列分析，两种 Gr. indica 和 Ph. stantoni 标本的 L. martiniquensis 和 L. donovani 复合体的扩增均呈阳性，前者被认为是土生土长的，后者则不是。使用 SSU rRNA-PCR 还对无尾目锥虫进行了分子检测，在除 Se. hivernus 之外的四种主要沙蝇物种的 16 个标本中普遍发现。
获得的序列可以通过系统发育分为两个主要的两栖动物分支（An04/Frog1 和 An01+An02/Frog2）。单系亚群和独特谱系的存在表明它们是新的锥虫物种。这些无尾目锥虫序列的 TCS 网络分析还显示出高单倍型多样性（Hd=0.925±0.050），但核苷酸多样性低（π=0.019±0.009）。此外，在单个 Gr. indica 标本中还通过显微镜观察到了活体无尾目锥虫，支持了其媒介能力。重要的是，我们的数据证实了 Se. gemmea 的稀缺性，并首次发现了 L. martiniquensis、L. donovani 复合体和疑似新型无尾目锥虫 spp. 在白蛉沙蝇中的循环，暗示它们可能作为锥虫寄生虫的媒介。因此，本研究的新数据将极大地促进对锥虫传播复杂性的理解，并更有效地制定针对这种被忽视疾病的预防和控制措施。
