Plasmodium knowlesi: Reservoir Hosts and Tracking the Emergence in Humans and Macaques

PLoS Pathogens

Balbir Singh¹  David J. Conway²  Janet Cox-Singh³  Paul C. S. Divis³  Kim-Sung Lee³  Siti Khatijah Zakaria³  Roynston A. Julin³  Asmad Matusop⁴ 

[1] Centre for Infection, St. George's University of London, London, United Kingdom;Department of Pathogen Molecular Biology, London School of Hygiene and Tropical Medicine, London, United Kingdom;Malaria Research Centre, Faculty of Medicine and Health Sciences, University Malaysia Sarawak, Kuching, Sarawak, Malaysia;Sarawak State Health Department, Kuching, Sarawak, Malaysia

关键词: Macaque;    Malarial parasites;    Mitochondrial DNA;    Plasmodium;    Malaria;    Parasitic diseases;    Haplotypes;    DNA sequence analysis;   

DOI  :  10.1371/journal.ppat.1002015

学科分类：生物科学（综合）

来源: Public Library of Science

【 摘 要 】

Plasmodium knowlesi, a malaria parasite originally thought to be restricted to macaques in Southeast Asia, has recently been recognized as a significant cause of human malaria. Unlike the benign and morphologically similar P. malariae, these parasites can lead to fatal infections. Malaria parasites, including P. knowlesi, have not yet been detected in macaques of the Kapit Division of Malaysian Borneo, where the majority of human knowlesi malaria cases have been reported. In order to extend our understanding of the epidemiology and evolutionary history of P. knowlesi, we examined 108 wild macaques for malaria parasites and sequenced the circumsporozoite protein (csp) gene and mitochondrial (mt) DNA of P. knowlesi isolates derived from macaques and humans. We detected five species of Plasmodium (P. knowlesi, P. inui, P. cynomolgi, P. fieldi and P. coatneyi) in the long-tailed and pig-tailed macaques, and an extremely high prevalence of P. inui and P. knowlesi. Macaques had a higher number of P. knowlesi genotypes per infection than humans, and some diverse alleles of the P. knowlesi csp gene and certain mtDNA haplotypes were shared between both hosts. Analyses of DNA sequence data indicate that there are no mtDNA lineages associated exclusively with either host. Furthermore, our analyses of the mtDNA data reveal that P. knowlesi is derived from an ancestral parasite population that existed prior to human settlement in Southeast Asia, and underwent significant population expansion approximately 30,000–40,000 years ago. Our results indicate that human infections with P. knowlesi are not newly emergent in Southeast Asia and that knowlesi malaria is primarily a zoonosis with wild macaques as the reservoir hosts. However, ongoing ecological changes resulting from deforestation, with an associated increase in the human population, could enable this pathogenic species of Plasmodium to switch to humans as the preferred host.

【 授权许可】

CC BY