Zoonotic simian malaria parasites in free-ranging Macaca fascicularis macaques and human malaria patients in Thailand, with a note on genetic characterization of recent isolates

Narapakdeesakul D 1 , Pengsakul T 2 , Kaewparuehaschai M 3 , Thongsahuan S 3 , Moonmake S 4 , Lekcharoen P 5 Show all authors , Thanee S 6 , Pattaradilokrat S 7 , Kaewthamasorn M 8

Affiliations 

  • 1 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
  • 2 Health and Environmental Research Center, Faculty of Environmental Management, Prince of Songkla University, Songkhla 90110, Thailand
  • 3 Department of National Parks, Wildlife and Plant Conservation, Ministry of Natural Resources and Environment, Bangkok 10900, Thailand
  • 4 The Office of Disease Prevention and Control Region 12 Songkhla, Department of Disease Control, Ministry of Public Health, Songkhla 90000, Thailand
  • 5 Veterinary Public Health Graduate Program, Department of Veterinary Public Health, Faculty of Veterinary Science, Chulalongkorn University, Bangkok 10330, Thailand
  • 6 Veterinary Parasitology Research Unit, Department of Pathology, Faculty of Veterinary Science, Chulalongkorn University, Bangkok 10330, Thailand
  • 7 Department of Biology, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand
  • 8 Veterinary Parasitology Research Unit, Department of Pathology, Faculty of Veterinary Science, Chulalongkorn University, Bangkok 10330, Thailand. Electronic address: Morakot.k@chula.ac.th
Acta Trop, 2023 Dec;248:107030.
PMID: 37742788 DOI: 10.1016/j.actatropica.2023.107030

Abstract

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.

* Title and MeSH Headings from MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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