Chotelersak Kruawan, Machida Ryuichiro, Thipaksorn Apisit, Samung Yudthana, Ruangsittichai Jiraporn
Department of Microbiology, Faculty of Medicine, Srinakharinwirot University, Bangkok 10110, Thailand.
Sugadaira Research Station, Mountain Science Center, University of Tsukuba, Sugadaira-kogen 1278-294, Ueda, Nagano 386-2204, Japan.
Infect Genet Evol. 2025 Sep;133:105793. doi: 10.1016/j.meegid.2025.105793. Epub 2025 Jul 5.
Fleas are widespread ectoparasites found across the globe-even in polar regions-and exhibit low host specificity, allowing them to infest both humans and animals, including birds. They feed on the blood of their hosts and serve as vectors for various infectious diseases, particularly in tropical and subtropical regions. In this study, the COI barcodes and ultrastructural characteristics using scanning electron microscopy (SEM) were performed to confirm classical morphological identification of cat flea taxonomic levels. Four species of medically important Pulicidae fleas were collected from hosts in various provinces of Thailand and identified based on their distinctive morphological characteristics: Xenopsylla cheopis, Echidnophaga gallinacea, Ctenocephalides felis and Ctenocephalides orientis. Phylogenetic analyses and calculated sequence distance based on mitochondrial COI barcodes were performed. The four species clearly formed monophyletic groups with low intraspecific distance (0 % -0.24 %) and high interspecific distance (4.60 % -21.26 %). Ctenocephalides felis and C. orientis were separated at the closely related level and separated into distinct clusters, with a sequence distance of 8.42 %. and C. orientis has shown closely genetic relationship with C. canis (4.60 %). Scanning electron microscopy (SEM) revealed ultrastructural characteristics that clearly differentiate C. felis and C. orientis, including differences in head shape and minute bristles on the dorsal end of the antennal fossa. Specifically, C. felis frons are elongated and pointed anteriorly, whereas C. orientis frons are short and rounded anteriorly. Additionally, the C. orientis female has 3-4-minute bristles at the dorsal end of the antennal fossa, while this structure is absent in the C. felis female but present and numerous (with 13-18 bristles) in all males of the genus Ctenocephalides. Fleas were identified, and their sex or ambiguous structures were determined using a stereoscope or low-power binocular microscope. DNA barcoding and ultrastructural analysis using SEM for differentiation of structures of taxonomic significance are useful for subspecies/species identification.
跳蚤是广泛分布于全球的体外寄生虫，甚至在极地地区也有发现，并且宿主特异性较低，这使得它们能够寄生在包括人类和鸟类在内的人和动物身上。它们以宿主的血液为食，并作为各种传染病的传播媒介，尤其是在热带和亚热带地区。在本研究中，利用扫描电子显微镜（SEM）进行细胞色素氧化酶亚基I（COI）条形码分析和超微结构特征分析，以确认猫蚤分类水平的经典形态学鉴定。从泰国各省的宿主身上采集了四种具有医学重要性的蚤科跳蚤，并根据其独特的形态特征进行鉴定：印鼠客蚤、禽角头蚤、猫栉首蚤和东方栉首蚤。基于线粒体COI条形码进行了系统发育分析并计算了序列距离。这四个物种明显形成了单系群，种内距离较低（0% - 0.24%），种间距离较高（4.60% - 21.26%）。猫栉首蚤和东方栉首蚤在亲缘关系较近的水平上分开，并分成不同的簇，序列距离为8.42%。东方栉首蚤与犬栉首蚤显示出密切的遗传关系（4.60%）。扫描电子显微镜（SEM）揭示了超微结构特征，这些特征能够清楚地区分猫栉首蚤和东方栉首蚤，包括头部形状和触角窝背端微小刚毛的差异。具体而言，猫栉首蚤的额部细长且向前尖，而东方栉首蚤的额部短且前端圆润。此外，东方栉首蚤雌虫在触角窝背端有3 - 4根微小刚毛，而猫栉首蚤雌虫没有这种结构，但在栉首蚤属的所有雄虫中都有且数量众多（有13 - 18根刚毛）。使用体视显微镜或低倍双目显微镜鉴定跳蚤，并确定其性别或模糊结构。利用DNA条形码和扫描电子显微镜进行超微结构分析以区分具有分类学意义的结构，对于亚种/物种鉴定很有用。
