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Description of the final instar larva of Orthetrum borneense Kimmins, 1936 (Odonata, Libellulidae), using rearing and molecular methods

Steinhoff PO, Butler SG, Dow RA

Zootaxa, 2016 Feb 18;4083(1):99-108.
PMID: 27394221 DOI: 10.11646/zootaxa.4083.1.5

The final instar larva of Orthetrum borneense Kimmins, 1936, is described and figured for the first time based on exuviae from three male and six female larvae collected in Sarawak, Borneo (East Malaysia). It is compared with an early instar larva, which was matched to the adult O. borneense by DNA barcoding, and the known larvae of other species of this genus that occur in the region.

Matched MeSH terms: Borneo
Characterisation of a drug resistant strain of Plasmodium falciparum from Sabah

Clyde DF, McCarthy VC, Gilman RH, Miller RM

J Trop Med Hyg, 1973 Sep;76(9):226-30.
PMID: 4582746
Matched MeSH terms: Borneo
Endemic goiter in Sarawak, Borneo Island; prevalence and pathogenesis

Ogihara T, Oki K, Iida Y, Hayashi S

Endocrinol. Jpn., 1972 Jun;19(3):285-93.
PMID: 4117947
Matched MeSH terms: Borneo
Serum thyrotropin levels of natives in Sarawak, Borneo Island

Ogihara T, Yamamoto T, Fukuchi M, Oki K

J Clin Endocrinol Metab, 1972 Nov;35(5):711-5.
PMID: 5071341
Matched MeSH terms: Borneo
Human health risk assessment and bioaccumulation of trace metals in fish species collected from the Miri coast, Sarawak, Borneo

A A, R N, K P, Bing CH, R R

Mar Pollut Bull, 2018 Aug;133:655-663.
PMID: 30041362 DOI: 10.1016/j.marpolbul.2018.06.033

The concentrations of nine trace metals (Cr, Mn, Co, Ni, Cu, Zn, Rb, Cd, and Pb) were measured in different tissues of two pelagic and five demersal fish species collected from the Miri coast, Sarawak. The sequence of accumulation of trace metals in different tissues were: liver > gill > gonad > muscle. Zn (301.00 μg g-1) and Cd (0.10 μg g-1) was the maximum and minimum accumulated elements. According to the Hazard Index calculation, none of the elements will pose any adverse health effects to humans for both ingestion rates (normal and habitual fish consumers) proposed by USEPA, except for Pb and Cd in certain fish species. On the basis of the results, the level of elements in the edible muscle tissues of all the analyzed fish species from the Miri coast are below the maximum permissible limits of Malaysian and International seafood guideline values and safe for consumers.

Matched MeSH terms: Borneo
Fulltext Metabolic profiling and in vitro assessment of anthelmintic fractions of Picria fel-terrae Lour

Kumarasingha R, Karpe AV, Preston S, Yeo TC, Lim DSL, Tu CL, et al.

Int J Parasitol Drugs Drug Resist, 2016 12;6(3):171-178.
PMID: 27639945 DOI: 10.1016/j.ijpddr.2016.08.002

Anthelmintic resistance is widespread in gastrointestinal nematode populations, such that there is a consistent need to search for new anthelmintics. However, the cost of screening for new compounds is high and has a very low success rate. Using the knowledge of traditional healers from Borneo Rainforests (Sarawak, Malaysia), we have previously shown that some traditional medicinal plants are a rich source of potential new anthelmintic drug candidates. In this study, Picria fel-terrae Lour. plant extract, which has previously shown promising anthelmintic activities, was fractionated via the use of a solid phase extraction cartridge and each isolated fraction was then tested on free-living nematode Caenorhabditis elegans and the parasitic nematode Haemonchus contortus. We found that a single fraction was enriched for nematocidal activity, killing ≥90% of C. elegans adults and inhibiting the motility of exsheathed L3 of H. contortus, while having minimal cytotoxic activity in mammalian cell culture. Metabolic profiling and chemometric analysis of the effective fraction indicated medium chained fatty acids and phenolic acids were highly represented.

Matched MeSH terms: Borneo
Fulltext Swedish traveller with Plasmodium knowlesi malaria after visiting Malaysian Borneo

Bronner U, Divis PC, Färnert A, Singh B

Malar J, 2009 Jan 16;8:15.
PMID: 19146706 DOI: 10.1186/1475-2875-8-15

Plasmodium knowlesi is typically found in nature in macaques and has recently been recognized as the fifth species of Plasmodium causing malaria in human populations in south-east Asia. A case of knowlesi malaria is described in a Swedish man, who became ill after returning from a short visit to Malaysian Borneo in October 2006. His P. knowlesi infection was not detected using a rapid diagnostic test for malaria, but was confirmed by PCR and molecular characterization. He responded rapidly to treatment with mefloquine. Evaluation of rapid diagnostic kits with further samples from knowlesi malaria patients are necessary, since early identification and appropriate anti-malarial treatment of suspected cases are essential due to the rapid growth and potentially life-threatening nature of P. knowlesi. Physicians should be aware that knowlesi infection is an important differential diagnosis in febrile travellers, with a recent travel history to forested areas in south-east Asia, including short-term travellers who tested negative with rapid diagnostic tests.

Matched MeSH terms: Borneo
Fulltext Local human movement patterns and land use impact exposure to zoonotic malaria in Malaysian Borneo

Fornace KM, Alexander N, Abidin TR, Brock PM, Chua TH, Vythilingam I, et al.

Elife, 2019 10 22;8.
PMID: 31638575 DOI: 10.7554/eLife.47602

Human movement into insect vector and wildlife reservoir habitats determines zoonotic disease risks; however, few data are available to quantify the impact of land use on pathogen transmission. Here, we utilise GPS tracking devices and novel applications of ecological methods to develop fine-scale models of human space use relative to land cover to assess exposure to the zoonotic malaria Plasmodium knowlesi in Malaysian Borneo. Combining data with spatially explicit models of mosquito biting rates, we demonstrate the role of individual heterogeneities in local space use in disease exposure. At a community level, our data indicate that areas close to both secondary forest and houses have the highest probability of human P. knowlesi exposure, providing quantitative evidence for the importance of ecotones. Despite higher biting rates in forests, incorporating human movement and space use into exposure estimates illustrates the importance of intensified interactions between pathogens, insect vectors and people around habitat edges.

Matched MeSH terms: Borneo
Fulltext Trends and variations in the prescribing of secondary preventative cardiovascular therapies for non-ST elevation myocardial infarction (NSTEMI) in Malaysia

Venkatason P, Zaharan NL, Ismail MD, Wan Ahmad WA, Mahmood Zuhdi AS

Eur J Clin Pharmacol, 2018 Jul;74(7):953-960.
PMID: 29582106 DOI: 10.1007/s00228-018-2451-3

PURPOSE: Information is lacking on prescribing of preventative cardiovascular pharmacotherapies for patients with non-ST elevation myocardial infarction (NSTEMI) in the Asian region. This study examined the prescribing rate of these pharmacotherapies, comparing NSTEMI to STEMI, and variations across demographics and clinical factors within the NSTEMI group in the multi-ethnic Malaysian population.
METHODS: This is a retrospective analysis of the Malaysian National Cardiovascular Disease Database-Acute Coronary Syndrome registry from year 2006 to 2013 (n = 30,873). On-discharge pharmacotherapies examined were aspirin, ADP-antagonists, statins, ACE-inhibitors, angiotensin-II-receptor blockers, and beta-blockers. Multivariate logistic regression was used to calculate adjusted odds ratio of receiving individual pharmacotherapies according to patients' characteristics in NSTEMI patients (n = 11,390).
RESULTS: Prescribing rates for cardiovascular pharmacotherapies had significantly increased especially for ADP-antagonists (76%) in NSTEMI patients. More than 85% were prescribed statins and antiplatelets but rates remained significantly lower compared to STEMI. Women and those over 65 years old were less likely to be prescribed these pharmacotherapies compared to men and younger NSTEMI patients. Chinese and Indians were more likely to receive selected pharmacotherapies compared to Malays (main ethnicity). Geographical variations were observed; East Malaysian (Malaysian Borneo) patients were less likely to receive these compared to Western region of Malaysian Peninsular. Underprescribing in patients with risk factors such as diabetes were observed with other co-morbidities influencing prescribing selectively.
CONCLUSION: This study uncovers demographic and clinical variations in cardiovascular pharmacotherapies prescribing for NSTEMI. Concerted efforts by policy makers, specialty societies, and physicians are required focusing on elderly, women, Malays, East Malaysians, and high-risk patients.

Matched MeSH terms: Borneo
Fulltext Applicability of the stages of change and Weight Efficacy Lifestyle Questionnaire with natives of Sarawak, Malaysia

Chang CT

Rural Remote Health, 2007 Oct-Dec;7(4):864.
PMID: 18076311

INTRODUCTION: There is an increase in the prevalence of overweight and obesity in Malaysia. Besides prevalence studies, not much is known about either overweight or obese individuals. The objective of this study was to determine the stages of change in losing weight and the self-efficacy in eating control of three indigenous groups of overweight and obese adults in Sarawak, Malaysia.
METHODS: A cross-sectional study was conducted in one rural region in Sarawak using a purposive sample. A structured questionnaire, which included two scales: (1) Weight: Stages of change (SOC) to assess readiness to change; and (2) Weight Efficacy Lifestyle Questionnaire (WEL) (both adopted from the transtheoretical model of change); and a set of pre-tested questionnaires on socio-demographic data, the presence of health problems and self-assessment of weight appropriateness, was used to interview respondents.
RESULTS: The stage distribution for weight loss of these adults respondents (n = 271) showed that 60.5% (n = 164) were in the pre-contemplation stage, 20.7% (n = 56) were in the contemplation stage, 8.5% (n = 23) were in the preparation stage, and 8.9% (n = 24) were in the action stage, while only 1.5% (n = 4) were in the maintenance stage. Except for education, the stage differences were generally stable across age, sex, race, household income, presence or absence of health problem, self-perceived weight and presence of overweight or obesity. Respondents were least able to control their eating under social pressure and food availability, according to their WEL score.
CONCLUSION: A large proportion of the overweight or obese adults was not intending to lose weight. The factor structure of the two WEL original subscales enabled partial differentiation between respondents who were able or unable to resist eating in situations where there were availability of food and experienced physical discomfort. The study results indicate the importance of assessing individuals' SOC score in order to implement stage-matched intervention strategies. More studies should be performed in order to validate the WEL questionnaire for use with a Malaysian sample.

Matched MeSH terms: Borneo
Photodynamic activity of plant extracts from Sarawak, Borneo

Jong WW, Tan PJ, Kamarulzaman FA, Mejin M, Lim D, Ang I, et al.

Chem Biodivers, 2013 Aug;10(8):1475-86.
PMID: 23939795 DOI: 10.1002/cbdv.201200303

Photodynamic therapy (PDT) is a medical treatment that involves the irradiation of an administered photosensitizing drug with light of a particular wavelength to activate the photosensitizer to kill abnormal cells. To date, only a small number of photosensitizers have been clinically approved for PDT, and researchers continue to look for new molecules that have more desirable properties for clinical applications. Natural products have long been important sources of pharmaceuticals, and there is a great potential for discovery of novel chemotypes from under-explored biodiversities in the world. The objective of this study is to mine the terrestrial plants in Sarawak, Borneo Island, for new photosensitizers for PDT. In a screening program from 2004 to 2008, we prepared and studied 2,400 extracts from 888 plants for their photosensitizing activities. This report details the bioprospecting process, preparation and testing of extracts, analysis of the active samples, fractionation of four samples, and isolation and characterization of photosensitizers.

Matched MeSH terms: Borneo
Alterations in selected serum biochemistry values of free-ranging Bornean leopard cats (Prionailurus bengalensis borneoensis) captured by box traps

Nájera F, Hearn AJ, Ross J, Nathan S, Revuelta L

Vet Res Commun, 2014 Sep;38(3):265-9.
PMID: 24839119 DOI: 10.1007/s11259-014-9605-2

Box-traps for capturing wild cats are widely used by researchers since it is one of the most effective methods for trapping these species. Although they are extensively utilised, the effects on the physiology of trapped felids remain unclear. Researchers frequently make judgements regarding the safety of such capture devices by examination of external injuries but often fail to take into consideration other physiological parameters. To assess the effects of capture events on selected serum biochemistry values of free-ranging Bornean leopard cats (Prionailurus bengalensis borneoensis) six free-ranging leopard cats (four males, two females) were trapped by using box-traps in Sabah, Malaysian Borneo. Blood was collected by jugular venipucture after chemical immobilization with a mixture of tiletamine and zolazepam. Blood was analysed for 17 serum biochemistry parameters. The most consistent and significantly higher value found in both sexes was aspartate aminotransferase (AST), followed by high mean value of alanine aminotransferase (ALT). Both mean values exceeded the upper limit of the reference range for captive leopard cats. These results demonstrate that captured leopard cats by box-traps undergo physical exertion and consequently some type of muscle injury/damage. Researchers and wildlife managers should be aware of the physiological response of trapped felids when using box-traps. Devices that facilitate the prompt removal of leopard cats from the traps would be useful for researchers to avoid further damage while live trapping this species.

Matched MeSH terms: Borneo
Fulltext The significance of pyrogenic polycyclic aromatic hydrocarbons in Borneo peat core for the reconstruction of fire history

Kong SR, Yamamoto M, Shaari H, Hayashi R, Seki O, Mohd Tahir N, et al.

PLoS One, 2021;16(9):e0256853.
PMID: 34495997 DOI: 10.1371/journal.pone.0256853

The reconstruction of fire history is essential to understand the palaeoclimate and human history. Polycyclic aromatic hydrocarbons (PAHs) have been extensively used as a fire marker. In this work, the distribution of PAHs in Borneo peat archives was investigated to understand how PAHs reflect the palaeo-fire activity. In total, 52 peat samples were analysed from a Borneo peat core for the PAH analysis. Pyrogenic PAHs consist of 2-7 aromatic rings, some of which have methyl and ethyl groups. The results reveal that the concentration of pyrogenic PAHs fluctuated with the core depth. Compared to low-molecular-weight (LMW) PAHs, the high-molecular-weight (HMW) PAHs had a more similar depth variation to the charcoal abundance. This finding also suggests that the HMW PAHs were mainly formed at a local fire near the study area, while the LMW PAHs could be transported from remote locations.

Matched MeSH terms: Borneo
Environmental geochemistry of the abandoned Mamut Copper Mine (Sabah) Malaysia

van der Ent A, Edraki M

Environ Geochem Health, 2018 Feb;40(1):189-207.
PMID: 27848090 DOI: 10.1007/s10653-016-9892-3

The Mamut Copper Mine (MCM) located in Sabah (Malaysia) on Borneo Island was the only Cu-Au mine that operated in the country. During its operation (1975-1999), the mine produced 2.47 Mt of concentrate containing approximately 600,000 t of Cu, 45 t of Au and 294 t of Ag, and generated about 250 Mt of overburden and waste rocks and over 150 Mt of tailings, which were deposited at the 397 ha Lohan tailings storage facility, 15.8 km from the mine and 980 m lower in altitude. The MCM site presents challenges for environmental rehabilitation due to the presence of large volumes of sulphidic minerals wastes, the very high rainfall and the large volume of polluted mine pit water. This indicates that rehabilitation and treatment is costly, as for example, exceedingly large quantities of lime are needed for neutralisation of the acidic mine pit discharge. The MCM site has several unusual geochemical features on account of the concomitant occurrence of acid-forming sulphide porphyry rocks and alkaline serpentinite minerals, and unique biological features because of the very high plant diversity in its immediate surroundings. The site hence provides a valuable opportunity for researching natural acid neutralisation processes and mine rehabilitation in tropical areas. Today, the MCM site is surrounded by protected nature reserves (Kinabalu Park, a World Heritage Site, and Bukit Hampuan, a Class I Forest Reserve), and the environmental legacy prevents de-gazetting and inclusion in these protected area in the foreseeable future. This article presents a preliminary geochemical investigation of waste rocks, sediments, secondary precipitates, surface water chemistry and foliar elemental uptake in ferns, and discusses these results in light of their environmental significance for rehabilitation.

Matched MeSH terms: Borneo
Fulltext Clinical characteristics and mortality risk prediction in critically ill children in Malaysian Borneo

Ganesan I, Thomas T, Ng FE, Soo TL

Singapore Med J, 2014 May;55(5):261-5.
PMID: 24862750

INTRODUCTION: Mortality risk prediction scores are important for benchmarking quality of care in paediatric intensive care units (PICUs). We aimed to benchmark PICU outcomes at our hospital against the Pediatric Index of Mortality 2 (PIM2) mortality risk prediction score, and evaluate differences in diagnosis on admission and outcomes between Malaysian and immigrant children.

METHODS: We prospectively collected demographic and clinical data on paediatric medical patients admitted to the PICU of Sabah Women's and Children's Hospital in Kota Kinabalu, Sabah, Malaysia. The PIM2 risk score for mortality was tabulated.

RESULTS: Of the 131 patients who met the inclusion criteria, data was available for 115 patients. The mean age of the patients was 2.6 ± 3.8 years, with 79% of the cohort aged less than five years. Patients were mainly of Kadazan (38%) and Bajau (30%) descent, and 26% of patients were non-citizens. Leading diagnoses on admission were respiratory (37%), neurological (18%) and infectious (17%) disorders. Out of the 29 patients who died, 23 (79%) were Malaysians and the main mortality diagnostic categories were respiratory disorder (22%), septicaemia (22%), haemato-oncological disease (17%) and neurological disorder (13%). Calculated standardised mortality ratios (SMRs) were not significantly > 1 for any patient category for variables such as age and admission diagnosis. However, infants less than two years old with comorbidities were significantly worse (SMR 2.61, 95% confidence interval 1.02-6.66).

CONCLUSION: The patient profile at our centre was similar to that reported from other PICUs in Asia. The PIM2 score is a useful mortality risk prediction model for our population.

Matched MeSH terms: Borneo
Fulltext Investigation on the antimicrobial activities of gingers (Etlingera coccinea (Blume) S.Sakai & Nagam and Etlingera sessilanthera R.M.Sm.) endemic to Borneo

Daniel-Jambun D, Dwiyanto J, Lim YY, Tan JBL, Muhamad A, Yap SW, et al.

J Appl Microbiol, 2017 Oct;123(4):810-818.
PMID: 28708293 DOI: 10.1111/jam.13536

AIMS: To investigate the antimicrobial properties of Etlingera coccinea and Etlingera sessilanthera and to isolate and identify the antimicrobial compounds.
METHODS AND RESULTS: Extracts were obtained via sequential solvent extraction method using hexane, dichloromethane, ethyl acetate, methanol and water. Antimicrobial activity testing was done using broth microdilution assay against 17 strains of bacteria. The leaf hexane extract of E. coccinea and rhizome hexane extract of E. sessilanthera showed best antimicrobial activities, with minimum inhibitory concentration (MIC) values ranging from 0·016 to 1 mg ml-1 against Gram-positive bacteria. From these active extracts, two antimicrobials were isolated and identified as trans-2-dodecenal and 8(17),12-labdadiene-15,16-dial with MIC values ranging from 4 to 8 μg ml-1 against Bacillus cereus, Bacillus subtilis and Staphylococcus aureus.
CONCLUSION: Etlingera coccinea and E. sessilanthera demonstrated good antimicrobial activities against clinically relevant bacteria strains. The antimicrobial compounds isolated showed low MIC values, hence suggesting their potential use as antimicrobial agents.
SIGNIFICANCE AND IMPACT OF THE STUDY: This study is the first to identify the potent antimicrobials from these gingers. The antimicrobials isolated could potentially be developed further for use in treatment of bacterial infections. Also, this study warrants further research into other Etlingera species in search for more antimicrobial compounds.

Matched MeSH terms: Borneo
Fulltext Using metabarcoding to compare the suitability of two blood-feeding leech species for sampling mammalian diversity in North Borneo

Drinkwater R, Schnell IB, Bohmann K, Bernard H, Veron G, Clare E, et al.

Mol Ecol Resour, 2019 Jan;19(1):105-117.
PMID: 30225935 DOI: 10.1111/1755-0998.12943

The application of high-throughput sequencing (HTS) for metabarcoding of mixed samples offers new opportunities in conservation biology. Recently, the successful detection of prey DNA from the guts of leeches has raised the possibility that these, and other blood-feeding invertebrates, might serve as useful samplers of mammals. Yet little is known about whether sympatric leech species differ in their feeding preferences, and whether this has a bearing on their relative suitability for monitoring local mammalian diversity. To address these questions, we collected spatially matched samples of two congeneric leech species Haemadipsa picta and Haemadipsa sumatrana from lowland rainforest in Borneo. For each species, we pooled ~500 leeches into batches of 10 individuals, performed PCR to target a section of the mammalian 16S rRNA locus and undertook sequencing of amplicon libraries using an Illumina MiSeq. In total, we identified sequences from 14 mammalian genera, spanning nine families and five orders. We found greater numbers of detections, and higher diversity of OTUs, in H. picta compared with H. sumatrana, with rodents only present in the former leech species. However, comparison of samples from across the landscape revealed no significant difference in mammal community composition between the leech species. We therefore suggest that H. picta is the more suitable iDNA sampler in this degraded Bornean forest. We conclude that the choice of invertebrate sampler can influence the detectability of different mammal groups and that this should be accounted for when designing iDNA studies.

Matched MeSH terms: Borneo
Fulltext Impact of logging and forest conversion to oil palm plantations on soil bacterial communities in Borneo

Lee-Cruz L, Edwards DP, Tripathi BM, Adams JM

Appl Environ Microbiol, 2013 Dec;79(23):7290-7.
PMID: 24056463 DOI: 10.1128/AEM.02541-13

Tropical forests are being rapidly altered by logging and cleared for agriculture. Understanding the effects of these land use changes on soil bacteria, which constitute a large proportion of total biodiversity and perform important ecosystem functions, is a major conservation frontier. Here we studied the effects of logging history and forest conversion to oil palm plantations in Sabah, Borneo, on the soil bacterial community. We used paired-end Illumina sequencing of the 16S rRNA gene, V3 region, to compare the bacterial communities in primary, once-logged, and twice-logged forest and land converted to oil palm plantations. Bacteria were grouped into operational taxonomic units (OTUs) at the 97% similarity level, and OTU richness and local-scale α-diversity showed no difference between the various forest types and oil palm plantations. Focusing on the turnover of bacteria across space, true β-diversity was higher in oil palm plantation soil than in forest soil, whereas community dissimilarity-based metrics of β-diversity were only marginally different between habitats, suggesting that at large scales, oil palm plantation soil could have higher overall γ-diversity than forest soil, driven by a slightly more heterogeneous community across space. Clearance of primary and logged forest for oil palm plantations did, however, significantly impact the composition of soil bacterial communities, reflecting in part the loss of some forest bacteria, whereas primary and logged forests did not differ in composition. Overall, our results suggest that the soil bacteria of tropical forest are to some extent resilient or resistant to logging but that the impacts of forest conversion to oil palm plantations are more severe.

Matched MeSH terms: Borneo
Fulltext Forest contraction in north equatorial Southeast Asia during the Last Glacial Period

Wurster CM, Bird MI, Bull ID, Creed F, Bryant C, Dungait JA, et al.

Proc Natl Acad Sci U S A, 2010 Aug 31;107(35):15508-11.
PMID: 20660748 DOI: 10.1073/pnas.1005507107

Today, insular Southeast Asia is important for both its remarkably rich biodiversity and globally significant roles in atmospheric and oceanic circulation. Despite the fundamental importance of environmental history for diversity and conservation, there is little primary evidence concerning the nature of vegetation in north equatorial Southeast Asia during the Last Glacial Period (LGP). As a result, even the general distribution of vegetation during the Last Glacial Maximum is debated. Here we show, using the stable carbon isotope composition of ancient cave guano profiles, that there was a substantial forest contraction during the LGP on both peninsular Malaysia and Palawan, while rainforest was maintained in northern Borneo. These results directly support rainforest "refugia" hypotheses and provide evidence that environmental barriers likely reduced genetic mixing between Borneo and Sumatra flora and fauna. Moreover, it sheds light on possible early human dispersal events.

Matched MeSH terms: Borneo
Fulltext Plasmodium knowlesi: reservoir hosts and tracking the emergence in humans and macaques

Lee KS, Divis PC, Zakaria SK, Matusop A, Julin RA, Conway DJ, et al.

PLoS Pathog, 2011 Apr;7(4):e1002015.
PMID: 21490952 DOI: 10.1371/journal.ppat.1002015

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.

Matched MeSH terms: Borneo/epidemiology

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