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Human Plasmodium knowlesi infection in Ranong province, southwestern border of Thailand.

ABSTRACT: BACKGROUND: Plasmodium knowlesi, a simian malaria parasite, has been reported in humans in many Southeast Asian countries. In Thailand, most of the limited numbers of cases reported so far were from areas near neighbouring countries, including Myanmar. METHODS: Blood samples collected from 171 Thai and 248 Myanmese patients attending a malaria clinic in Ranong province, Thailand, located near the Myanmar border were investigated for P. knowlesi using nested PCR assays. Positive samples were also investigated by PCR for Plasmodium falciparum, Plasmodium vivax, Plasmodium malariae and Plasmodium ovale, and were confirmed by sequencing the gene encoding the circumsporozoite protein (csp). RESULTS: Two samples, one obtained from a Thai and the other a Myanmese, were positive for P. knowlesi only. Nucleotide sequences of the csp gene derived from these two patients were identical and phylogenetically indistinguishable from other P. knowlesi sequences derived from monkeys and humans. Both patients worked in Koh Song, located in the Kawthoung district of Myanmar, which borders Thailand. CONCLUSION: This study indicates that transmission of P. knowlesi is occurring in the Ranong province of Thailand or the Kawthoung district of Myanmar. Further studies are required to assess the incidence of knowlesi malaria and whether macaques in these areas are the source of the infections.

SUBMITTER: Sermwittayawong N

PROVIDER: S-EPMC3293766 | biostudies-literature | 2012

REPOSITORIES: biostudies-literature

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Human Plasmodium knowlesi infection in Ranong province, southwestern border of Thailand.

Sermwittayawong Natthawan N Singh Balbir B Nishibuchi Mitsuaki M Sawangjaroen Nongyao N Vuddhakul Varaporn V

Malaria journal 20120208

<h4>Background</h4>Plasmodium knowlesi, a simian malaria parasite, has been reported in humans in many Southeast Asian countries. In Thailand, most of the limited numbers of cases reported so far were from areas near neighbouring countries, including Myanmar.<h4>Methods</h4>Blood samples collected from 171 Thai and 248 Myanmese patients attending a malaria clinic in Ranong province, Thailand, located near the Myanmar border were investigated for P. knowlesi using nested PCR assays. Positive samp ...[more]

PMID: 22313518

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Project description:To date, four species of simian malaria parasites including Plasmodium knowlesi, P. cynomolgi, P. inui and P. fieldi have been incriminated in human infections in Thailand. Although the prevalence of malaria in macaque natural hosts has been investigated, their vectors remain unknown in this country. Herein, we performed a survey of Anopheles mosquitoes during rainy and dry seasons in Narathiwat Province, Southern Thailand. Altogether 367 Anopheles mosquitoes were captured for 40 nights during 18:00 to 06:00 h by using human-landing catches. Based on morphological and molecular identification, species composition comprised An. maculatus (37.06%), An. barbirostris s.l. (31.34%), An. latens (17.71%), An. introlatus (10.08%) and others (3.81%) including An. umbrosus s.l., An. minimus, An. hyrcanus s.l., An. aconitus, An. macarthuri and An. kochi. Analyses of individual mosquitoes by PCR, sequencing and phylogenetic inference of the mitochondrial cytochrome genes of both malaria parasites and mosquitoes have revealed that the salivary gland samples of An. latens harbored P. knowlesi (n = 1), P. inui (n = 2), P. fieldi (n = 1), P. coatneyi (n = 1), P. hylobati (n = 1) and an unnamed Plasmodium species known to infect both long-tailed and pig-tailed macaques (n = 2). The salivary glands of An. introlatus possessed P. cynomolgi (n = 1), P. inui (n = 1), P. hylobati (n = 1) and coexistence of P. knowlesi and P. inui (n = 1). An avian malaria parasite P. juxtanucleare has been identified in the salivary gland sample of An. latens. Three other distinct lineages of Plasmodium with phylogenetic affinity to avian malaria species were detected in An. latens, An. introlatus and An. macarthuri. Interestingly, the salivary gland sample of An. maculatus contained P. caprae, an ungulate malaria parasite known to infect domestic goats. Most infected mosquitoes harbored multiclonal Plasmodium infections. All Plasmodium-infected mosquitoes were captured during the first quarter of the night and predominantly occurred during rainy season. Since simian malaria in humans has a wide geographic distribution in Thailand, further studies in other endemic areas of the country are mandatory for understanding transmission and prevention of zoonotic malaria.

Project description:BackgroundThailand is committed to eliminating malaria by 2024. From 2013 to 2020, the total number of malaria cases have decreased, from 37,741 to 4474 (an 88.1% reduction). However, infections with Plasmodium knowlesi, a monkey malarial pathogen that can also infect humans, have been increasingly observed. This study focused on the molecular analysis of P. knowlesi parasites causing malaria in Thailand.MethodsUnder Thailand's integrated Drug Efficacy Surveillance (iDES), which includes drug-resistance monitoring as part of routine case-based surveillance and responses, specimens were collected from malaria patients (n = 966) between 2018 and 2020. Thirty-one mono P. knowlesi infections (3.1%), most of which were from eastern and southern Thailand, were observed and confirmed by nested PCR assay and DNA sequencing. To evaluate whether these pathogens were from different lineages, cluster analysis based on seven microsatellite genotyping markers and the merozoite surface protein 1 (pkmsp1) gene was carried out. The P. knowlesi pyrimethamine resistance gene dihydrofolate reductase (pkdhfr) was sequenced and homology modelling was constructed.ResultsThe results of analysing the seven microsatellite markers and pkmsp1 sequence demonstrated that P. knowlesi parasites from eastern Thailand were of the same lineage as those isolated in Cambodia, while the parasites causing malaria in southern Thailand were the same lineage as those isolated from Malaysia. The sequencing results for the pkdhfr genes indicated the presence of two mutations, Arg34Leu and a deletion at position 105. On analysis with homology modelling, the two mutations were not associated with anti-malarial drug resistance.ConclusionsThis report compared the genetic populations of P. knowlesi parasites in Thailand from 2018 to 2020 and have shown similar lineages as those isolated in Cambodia and Malaysia of P. knowlesi infection in Thailand and demonstrated that the P. knowlesi parasites were of the same lineages as those isolated in Cambodia and Malaysia. The parasites were also shown to be sensitive to pyrimethamine.

Dataset Information

Human Plasmodium knowlesi infection in Ranong province, southwestern border of Thailand.

Publications

Human Plasmodium knowlesi infection in Ranong province, southwestern border of Thailand.

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