Veterinary Pathobiology Graduate Program, Department of Pathology, Faculty of Veterinary Science, Chulalongkorn University, Bangkok 10330, Thailand; Veterinary Parasitology Research Unit, Department of Pathology, Faculty of Veterinary Science, Chulalongkorn University, Bangkok 10330, Thailand.
Health and Environmental Research Center, Faculty of Environmental Management, Prince of Songkla University, Songkhla 90110, Thailand.
Acta Trop. 2023 Dec;248:107030. doi: 10.1016/j.actatropica.2023.107030. Epub 2023 Sep 22.
Despite the natural occurrences of human infections by Plasmodium knowlesi, P. cynomolgi, P. inui, and P. fieldi in Thailand, investigating the prevalence and genetic diversity of the zoonotic simian malaria parasites in macaque populations has been limited to certain areas. To address this gap, a total of 560 long-tailed macaques (Macaca fascicularis) and 20 southern pig-tailed macaques (M. nemestrina) were captured from 15 locations across 10 provinces throughout Thailand between 2018 and 2021 for investigation of malaria, as were 15 human samples residing in two simian-malaria endemic provinces, namely Songkhla and Satun, who exhibited malaria-like symptoms. Using PCR techniques targeting the mitochondrial cytb and cox1 genes coupled with DNA sequencing, 40 long-tailed macaques inhabiting five locations had mono-infections with one of the three simian malaria species. Most of the positive cases of macaque were infected with P. inui (32/40), while infections with P. cynomolgi (6/40) and P. knowlesi (2/40) were less common and confined to specific macaque populations. Interestingly, all 15 human cases were mono-infected with P. knowlesi, with one of them residing in an area with two P. knowlesi-infected macaques. Nucleotide sequence analysis showed a high level of genetic diversity in P. inui, while P. cynomolgi and P. knowlesi displayed limited genetic diversity. Phylogenetic and haplotype network analyses revealed that P. inui in this study was closely related to simian and Anopheles isolates from Peninsular Malaysia, while P. cynomolgi clustered with simian and human isolates from Asian countries. P. knowlesi, which was found in both macaques and humans in this study, was closely related to isolates from macaques, humans, and An. hackeri in Peninsular Malaysia, suggesting a sylvatic transmission cycle extending across these endemic regions. This study highlights the current hotspots for zoonotic simian malaria and sheds light on the genetic characteristics of recent isolates in both macaques and human residents in Thailand.
尽管在泰国已经发现了人类感染疟原虫 knowlesi、疟原虫 cynomolgi、疟原虫 inui 和疟原虫 fieldi 的自然病例，但对猴群中这些人畜共患灵长类疟原虫的流行情况和遗传多样性的研究仅限于某些地区。为了解决这一差距，我们于 2018 年至 2021 年期间，从泰国 10 个省的 15 个地点共捕获了 560 只长尾猕猴（Macaca fascicularis）和 20 只南方猪尾猕猴（M. nemestrina），并对来自两个灵长类疟疾病区（宋卡府和沙敦府）的 15 名居住在这些地区的人类样本进行了疟疾调查，这些人表现出疟疾样症状。使用针对线粒体 cytb 和 cox1 基因的 PCR 技术结合 DNA 测序，我们发现栖息在五个地点的 40 只长尾猕猴感染了三种灵长类疟原虫中的一种。在感染的猕猴中，大多数阳性病例感染了疟原虫 inui（32/40），而感染疟原虫 cynomolgi（6/40）和疟原虫 knowlesi（2/40）的情况较少见，且局限于特定的猕猴群体。有趣的是，所有 15 例人类病例均感染了疟原虫 knowlesi，其中 1 例居住在两个感染疟原虫 knowlesi 的猕猴地区。核苷酸序列分析显示，疟原虫 inui 具有高度的遗传多样性，而疟原虫 cynomolgi 和疟原虫 knowlesi 的遗传多样性有限。系统发生和单倍型网络分析显示，本研究中的疟原虫 inui 与来自马来半岛的灵长类和按蚊分离株密切相关，而疟原虫 cynomolgi 与来自亚洲国家的灵长类和人类分离株聚类。本研究中在猕猴和人类中发现的疟原虫 knowlesi 与来自马来半岛的猕猴、人类和按蚊 hackeri 的分离株密切相关，这表明一个跨越这些流行地区的森林传播循环。本研究突出了目前人畜共患灵长类疟原虫的热点，并阐明了泰国猕猴和人类居民中最近分离株的遗传特征。
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