Displaying publications 1 - 20 of 46 in total

  1. Zhang X, Uchiyama Y, Nakayama A
    Mar. Pollut. Bull., 2019 Jul;144:265-274.
    PMID: 31179996 DOI: 10.1016/j.marpolbul.2019.04.050
    An Eulerian passive tracer model coupled with a quadruple-nested 3D circulation model was used to assess the coastal dispersal of treated wastewater effluent from a sewage treatment plant and the associated impacts on an adjacent seaweed farm using three different operational scenarios. When the discharged volume and source effluent fluxes were decreased by ~16.7%, the accumulated effluent in the farm was reduced by ~25.4%. A tracer flux budget analysis revealed the apparent predominance of the transient component that accounts for the nonlinear interactions primarily from tidal currents and eddies. The transient flux promoted the effluent influx to impede effluent accumulation in the farm, whereas the mean flux contributed to the outgoing flux. A source flux reduction caused a remarkable decrease in the transient flux and thus an even greater effluent accumulation reduction. In turn, a modified source density scenario without total effluent volume change did not work as expected.
  2. Zhang X, Tan Z, Jia K, Zhang W, Dang M
    Artif Cells Nanomed Biotechnol, 2019 Dec;47(1):2171-2178.
    PMID: 31159596 DOI: 10.1080/21691401.2019.1620249
    Nanomedicine is a rapidly emerging field and is reported to be a promising tool for treating various diseases. Green synthesized nanoparticles are documented to possess a potent anticancer effect. Rabdosia rubescens is a Chinese plant which is also one of the components of PC-SPES and used to treat prostate cancer. In the present study, we synthesized the gold nanoparticles from R. rubescens (RR-AuNP) and analyzed its anticancer activity against the lung carcinoma A549 cell lines. Since lung cancer is reported to be with increased morbidity and decreased survival rate. The biosynthesized RR-AuNP were confirmed using UV-Visible spectrophotometer, size and shape of RR-AuNP were assessed by DLS, TEM and EDX. The biomolecules present in RR-AuNP and its topographical structure were detected using FTIR, SAED and AFM analysis. MTT assay was performed to detect the IC50 dose of RR-AuNP and its apoptotic effect was assessed by detecting the caspases activation, ROS generation. The anticancer effect of RR-AuNP was confirmed by DAPI staining, TUNEL assay and its molecular mechanism were confirmed by assessing the apoptotic signalling molecules protein expression. Our results illustrate that RR-AuNP showed a strong absorption peak at 550 nm and the RRAuNP were polydispersed nanospheres with size of 130 nm. RR-AuNP IC50 dose against A549 lung carcinoma cell line was detected to be at 25 µg/ml. The results of DAPI staining, TUNEL and immunoblotting analysis confirms both the 25 µg/ml and 50 µg/ml of RR-AuNP possess potent anticancer and apoptotic effect, suggesting that RR-AuNP that it may be a persuasive molecule to treat lung cancer.
  3. Tan SS, Aminah A, Zhang XG, Abdul SB
    Meat Sci., 2006 Mar;72(3):387-97.
    PMID: 22061722 DOI: 10.1016/j.meatsci.2005.07.012
    This study was designed to explore the potential of refined, bleached and deodorized (RBD) palm oil (PO) and palm stearin (POs) utilization in chicken frankfurters. A 10 points augmented simplex-centroid design was used to study the effect of chicken fat (CF), PO and POs as well as the interaction of these fats on the emulsion, textural and sensory properties of chicken frankfurters. All frankfurters were formulated to contain approx 25% fat, 52% moisture and 10% protein. No significant difference was found in end chopping temperatures of all meat batters even though the temperature of PO and POs upon incorporation into meat batters was 50°C higher than CF. Strong emulsions were formed as no fluid losses were observed in all the meat batters tested after heating. Texture profiles of the frankfurters containing PO and/or CF were quite similar, but increment of POs raised hardness, chewiness, and shear hardness of the frankfurters. Acceptability of the frankfurters was evaluated using hedonic test. Panelists found no difference in hardness preference between frankfurters made from totally CF and PO, while frankfurters made from POs were rated as hard and brittle. CF was important in determining acceptability of the frankfurters, as reduction of CF in formulation resulted in lower scores in chicken flavor, juiciness, oiliness and overall acceptance of the frankfurters. Frankfurters with sensory acceptability comparable to a commercial one were found to comprise of more than 17% CF, and less than 67% PO and 17% POs of the fat blend.
  4. Jiang H, Xiang X, Hao W, Room R, Zhang X, Wang X
    PMID: 29761160 DOI: 10.1186/s41256-018-0070-2
    Background: The paper reviews alcohol consumption patterns and alcohol-related social and health issues among 15-29-year old young people in Asian countries, and discusses strategies for preventing and controlling alcohol use and related harms.

    Methods: We searched Google Scholar, PubMed, and Web of Science for reports, reviews and journal articles published in English between 1st Jan 1990 and 31st August 2016.

    Results: Forty-one reports, reviews and journal papers were identified and included in the final review. The current drinking levels and prevalence among young people are markedly different between eight included Asian countries, ranging from 4.2% in Malaysia to 49.3% in China. In a majority of the selected Asian countries, over 15% of total deaths among young men and 6% among young women aged 15-29 years are attributable to alcohol use. Alcohol use among young people is associated with a number of harms, including stress, family violence, injuries, suicide, and sexual and other risky behaviours. Alcohol policies, such as controlling sales, social supply and marketing, setting up/raising a legal drinking age, adding health warning labels on alcohol containers, and developing a surveillance system to monitor drinking pattern and risky drinking behaviour, could be potential means to reduce harmful use of alcohol and related harm among young people in Asia.

    Conclusions: The review reveals that drinking patterns and behaviours vary across eight selected Asian countries due to culture, policies and regional variations. The research evidence holds substantial policy implications for harm reduction on alcohol drinking among young people in Asian countries -- especially for China, which has almost no alcohol control policies at present.

  5. Uchiyama Y, Zhang X, Suzue Y, Kosako T, Miyazawa Y, Nakayama A
    Mar. Pollut. Bull., 2018 May;130:40-54.
    PMID: 29866568 DOI: 10.1016/j.marpolbul.2018.03.007
    A high-resolution 3-D model was developed to assess the impact of a diversion outfall at the Tarumi Sewage Treatment Plant (TSTP) on an adjacent seaweed farm in Osaka Bay, Japan. The model was extensively validated to ensure a reasonable agreement with in situ observations. The western part of the farm is largely influenced by tidal currents, whereas the eastern area is mainly affected by subtidal residual currents that are primarily due to surface wind stress. The released effluent is transported by counterclockwise residual circulation formed off the TSTP. The model reveals that the diversion adequately suppresses the influence on the farm. While the instantaneous effluent concentration is diminished by about 50%, the effluent accumulated on the farm decreased from 2.83 × 104 m3 to 2.01 × 104 m3 due to the diversion, demonstrating an approximately 28% reduction of the effluent from the TSTP by the diversion outfall.
  6. Muhamad HM, Xu X, Zhang X, Jaaman SA, Muda AM
    J. Acoust. Soc. Am., 2018 05;143(5):2708.
    PMID: 29857727 DOI: 10.1121/1.5036926
    Studies of Irrawaddy dolphins' acoustics assist in understanding the behaviour of the species and thereby conservation of this species. Whistle signals emitted by Irrawaddy dolphin within the Bay of Brunei in Malaysian waters were characterized. A total of 199 whistles were analysed from seven sightings between January and April 2016. Six types of whistles contours named constant, upsweep, downsweep, concave, convex, and sine were detected when the dolphins engaged in traveling, foraging, and socializing activities. The whistle durations ranged between 0.06 and 3.86 s. The minimum frequency recorded was 443 Hz [Mean = 6000 Hz, standard deviation (SD) = 2320 Hz] and the maximum frequency recorded was 16 071 Hz (Mean = 7139 Hz, SD = 2522 Hz). The mean frequency range (F.R.) for the whistles was 1148 Hz (Minimum F.R. = 0 Hz, Maximum F.R. = 4446 Hz; SD = 876 Hz). Whistles in the Bay of Brunei were compared with population recorded from the waters of Matang and Kalimantan. The comparisons showed differences in whistle duration, minimum frequency, start frequency, and number of inflection point. Variation in whistle occurrence and frequency may be associated with surface behaviour, ambient noise, and recording limitation. This will be an important element when planning a monitoring program.
  7. Zhao P, Wang Y, Zhang Y, Guo T, Zhang Z, Zhang WJ, et al.
    Saudi J Biol Sci, 2016 May;23(3):353-7.
    PMID: 27081360 DOI: 10.1016/j.sjbs.2015.08.007
    In this study, the selenium enriched peanuts and the different solubility proteins extracted from them were investigated. The dried defatted selenium enriched peanuts (SeP) powder (0.3147 μg/g) had a 2.5-fold higher mean total selenium concentration than general peanuts (GP) power (0.1233 μg/g). The SeP had higher concentration of selenium, manganese and zinc than that of GP, but less calcium. The rate of extraction of protein was 23.39% for peanuts and alkali soluble protein was the main component of protein in SeP, which accounted for 92.82% of total soluble protein and combined selenium was 77.33% of total selenium protein. In different forms of proteins from SeP, the WSePr due to higher concentration of selenium had higher DPPH free-radical scavenging activity, higher reducing activity and longer induction time than other proteins.
  8. Zhang X, Wu X, Centeno A, Ryan MP, Alford NM, Riley DJ, et al.
    Sci Rep, 2016;6:23364.
    PMID: 26997140 DOI: 10.1038/srep23364
    Copper zinc tin sulfide (CZTS) is a promising material for harvesting solar energy due to its abundance and non-toxicity. However, its poor performance hinders their wide application. In this paper gold (Au) nanoparticles are successfully incorporated into CZTS to form Au@CZTS core-shell nanostructures. The photocathode of Au@CZTS nanostructures exhibits enhanced optical absorption characteristics and improved incident photon-to-current efficiency (IPCE) performance. It is demonstrated that using this photocathode there is a significant increase of the power conversion efficiency (PCE) of a photoelectrochemical solar cell of 100% compared to using a CZTS without Au core. More importantly, the PCE of Au@CZTS photocathode improved by 15.8% compared to standard platinum (Pt) counter electrode. The increased efficiency is attributed to plasmon resonance energy transfer (PRET) between the Au nanoparticle core and the CZTS shell at wavelengths shorter than the localized surface plasmon resonance (LSPR) peak of the Au and the semiconductor bandgap.
  9. Koh MT, Liu CS, Chiu CH, Boonsawat W, Watanaveeradej V, Abdullah N, et al.
    Epidemiol. Infect., 2016 Apr;144(6):1192-200.
    PMID: 26468043 DOI: 10.1017/S0950268815002393
    Surveillance data on the burden of pertussis in Asian adults are limited. This cross-sectional study evaluated the prevalence of serologically confirmed pertussis in adults with prolonged cough in Malaysia, Taiwan and Thailand. Adults (⩾19 years) with cough lasting for ⩾14 days without other known underlying cause were enrolled from outpatient clinics of seven public and/or private hospitals. Single blood samples for anti-pertussis toxin antibodies (anti-PT IgG) were analysed and economic impact and health-related quality of life (EQ-5D) questionnaires assessed. Sixteen (5·13%) of the 312 chronically coughing adults had serological evidence of pertussis infection within the previous 12 months (anti-PT IgG titre ⩾62·5 IU/ml). Three of them were teachers. Longer duration of cough, paroxysms (75% seroconfirmed, 48% non-seroconfirmed) and breathlessness/chest pain (63% seroconfirmed, 36% non-seroconfirmed) were associated with pertussis (P < 0·04). Of the seroconfirmed patients, the median total direct medical cost per pertussis episode in public hospitals (including physician consultations and/or emergency room visits) was US$13 in Malaysia, US$83 in Taiwan (n = 1) and US$26 in Thailand. The overall median EQ-5D index score of cases was 0·72 (range 0·42-1·00). Pertussis should be considered in the aetiology of adults with a prolonged or paroxysmal cough, and vaccination programmes considered.
    Study site in Malaysia: Klinik Kesihatan Seremban, Negeri Sembilan; Primary Care Clinic, University Malaya Medical Centre (UMMC), Kuala Lumpur, Malaysia
  10. Zubir NA, Yacou C, Motuzas J, Zhang X, Diniz da Costa JC
    Sci Rep, 2014;4:4594.
    PMID: 24699690 DOI: 10.1038/srep04594
    Graphene oxide-iron oxide (GO-Fe3O4) nanocomposites were synthesised by co-precipitating iron salts onto GO sheets in basic solution. The results showed that formation of two distinct structures was dependent upon the GO loading. The first structure corresponds to a low GO loading up to 10 wt%, associated with the beneficial intercalation of GO within Fe3O4 nanoparticles and resulting in higher surface area up to 409 m(2) g(-1). High GO loading beyond 10 wt% led to the aggregation of Fe3O4 nanoparticles and the undesirable stacking of GO sheets. The presence of strong interfacial interactions (Fe-O-C bonds) between both components at low GO loading lead to 20% higher degradation of Acid Orange 7 than the Fe3O4 nanoparticles in heterogeneous Fenton-like reaction. This behaviour was attributed to synergistic structural and functional effect of the combined GO and Fe3O4 nanoparticles.
  11. Wang L, Li Y, Huang G, Zhang X, Pingguan-Murphy B, Gao B, et al.
    Crit. Rev. Biotechnol., 2016 Jun;36(3):553-65.
    PMID: 25641330 DOI: 10.3109/07388551.2014.993588
    Natural cellular microenvironment consists of spatiotemporal gradients of multiple physical (e.g. extracellular matrix stiffness, porosity and stress/strain) and chemical cues (e.g. morphogens), which play important roles in regulating cell behaviors including spreading, proliferation, migration, differentiation and apoptosis, especially for pathological processes such as tumor formation and progression. Therefore, it is essential to engineer cellular gradient microenvironment incorporating various gradients for the fabrication of normal and pathological tissue models in vitro. In this article, we firstly review the development of engineering cellular physical and chemical gradients with cytocompatible hydrogels in both two-dimension and three-dimension formats. We then present current advances in the application of engineered gradient microenvironments for the fabrication of disease models in vitro. Finally, concluding remarks and future perspectives for engineering cellular gradients are given.
  12. Gao B, Wang L, Han S, Pingguan-Murphy B, Zhang X, Xu F
    Crit. Rev. Biotechnol., 2016 Aug;36(4):619-29.
    PMID: 25669871 DOI: 10.3109/07388551.2014.1002381
    Diabetes now is the most common chronic disease in the world inducing heavy burden for the people's health. Based on this, diabetes research such as islet function has become a hot topic in medical institutes of the world. Today, in medical institutes, the conventional experiment platform in vitro is monolayer cell culture. However, with the development of micro- and nano-technologies, several microengineering methods have been developed to fabricate three-dimensional (3D) islet models in vitro which can better mimic the islet of pancreases in vivo. These in vitro islet models have shown better cell function than monolayer cells, indicating their great potential as better experimental platforms to elucidate islet behaviors under both physiological and pathological conditions, such as the molecular mechanisms of diabetes and clinical islet transplantation. In this review, we present the state-of-the-art advances in the microengineering methods for fabricating microscale islet models in vitro. We hope this will help researchers to better understand the progress in the engineering 3D islet models and their biomedical applications such as drug screening and islet transplantation.
  13. Bukhari SN, Zhang X, Jantan I, Zhu HL, Amjad MW, Masand VH
    Chem Biol Drug Des, 2015 Jun;85(6):729-42.
    PMID: 25328063 DOI: 10.1111/cbdd.12457
    A novel series of 1,3-diphenyl-2-propen-1-one (chalcone) derivatives was synthesized by a simple, eco-friendly, and efficient Claisen-Schmidt condensation reaction and used as precursors for the synthesis of new pyrazoline derivatives. All the synthesized compounds were screened for anti-inflammatory related activities such as inhibition of phospholipase A(2) (PLA(2)), cyclooxygenases (COX-1 and COX-2), IL-6, and TNF-α. The results of the above studies show that the compounds synthesized are effective inhibitors of above pro-inflammatory enzymes and cytokines. Overall, the results of the studies reveal that the pyrazolines with chlorophenyl substitution (1b-6b) seem to be important for inhibition of enzymes and cytokines. Molecular docking experiments were performed to clarify the molecular aspects of the observed COX-inhibitory activities of the investigated compounds.
  14. Imafuku S, Zheng M, Tada Y, Zhang X, Theng C, Thevarajah S, et al.
    J. Dermatol., 2018 Jul;45(7):805-811.
    PMID: 29740870 DOI: 10.1111/1346-8138.14338
    A working group of dermatologists in Asian countries assessed the current status of psoriatic management in the region to prepare a consensus report on topical treatment in mild to moderate plaque psoriasis. Even though the association of psoriasis with systemic comorbidities is increasingly acknowledged, psoriasis is still lower in health-care priority lists in the region. The psychosocial impact of psoriasis may be greater in Asian countries due to cultural norms and social discrimination. Non-adherence to treatment is also common among Asians. The current care given to patients with mild to moderate psoriasis needs to be streamlined, enhanced and organized with a patient-centered care approach to achieve better outcomes. A comprehensive assessment of the disease severity and its impact on a patient's life is required before initiating treatment. Education and active involvement of the patient in the treatment plan is an important part of psoriatic management. It is recommended to personalize topical treatment to meet the needs of the patient, depending on disease severity, psychosocial impact, the patient's expectations and, more importantly, the patient's willingness and ability to actively follow the treatment procedure. Fixed-dose combination of corticosteroid and vitamin D analogs is the preferred topical medication for both initial and maintenance phases of treatment. The fast containment of the disease is the goal of the initial phase of 4-8 weeks and it demands a potent fast-acting topical therapy. Satisfactory control of the disease and prevention of relapses should be achieved during the maintenance phase with twice a week or weekend applications.
  15. Chen Y, Huang J, Yeap ZQ, Zhang X, Wu S, Ng CH, et al.
    Spectrochim Acta A Mol Biomol Spectrosc, 2018 Jun 15;199:271-282.
    PMID: 29626818 DOI: 10.1016/j.saa.2018.03.061
    Anoectochilus roxburghii (Wall.) Lindl. (Orchidaceae) is a precious traditional Chinese medicinal herb and has been perennially used to treat various illness. However, there were unethical sellers who adulterated wild A. roxburghii with tissue cultured and cultivated ones. Therefore, there is an urgent need for an effective authentication method to differentiate between these different types of A. roxburghii. In this research, the infrared spectroscopic tri-step identification approach including Fourier transform infrared spectroscopy (FT-IR), Second derivative infrared spectra (SD-IR) and two-dimensional correlation infrared spectra (2D-IR) was used to develop a simple and rapid method to discriminate between wild, cultivated and tissue cultivated A. roxburghii plant. Through this study, all three types of A. roxburghii plant were successfully identified and discriminated through the infrared spectroscopic tri-step identification method. Besides that, all the samples of wild, cultivated and tissue cultivated A. roxburghii plant were analysed with the Soft Independent Modelling of Class Analogy (SIMCA) pattern recognition technique to test and verify the experimental results. The results showed that the three types of A. roxburghii can be discriminated clearly as the recognition rate was 100% for all three types and the rejection rate was more than 60%. 70% of the validated samples were also identified correctly by the SIMCA model. The SIMCA model was also validated by comparing 70 standard herbs to the model. As a result, it was demonstrated that the macroscopic IR fingerprint method and the classification analysis could discriminate not only between the A. roxburghi samples and the standard herbs, it could also distinguish between the three different types of A. roxburghi plant in a direct, rapid and holistic manner.
  16. Han YL, Wang S, Zhang X, Li Y, Huang G, Qi H, et al.
    Drug Discov. Today, 2014 Jun;19(6):763-73.
    PMID: 24508818 DOI: 10.1016/j.drudis.2014.01.015
    Regenerative medicine has rapidly evolved over the past decade owing to its potential applications to improve human health. Targeted differentiations of stem cells promise to regenerate a variety of tissues and/or organs despite significant challenges. Recent studies have demonstrated the vital role of the physical microenvironment in regulating stem cell fate and improving differentiation efficiency. In this review, we summarize the main physical cues that are crucial for controlling stem cell differentiation. Recent advances in the technologies for the construction of physical microenvironment and their implications in controlling stem cell fate are also highlighted.
  17. Shi M, Ling K, Yong KW, Li Y, Feng S, Zhang X, et al.
    Sci Rep, 2015 Dec 14;5:17928.
    PMID: 26655688 DOI: 10.1038/srep17928
    Cryopreservation is the most promising way for long-term storage of biological samples e.g., single cells and cellular structures. Among various cryopreservation methods, vitrification is advantageous by employing high cooling rate to avoid the formation of harmful ice crystals in cells. Most existing vitrification methods adopt direct contact of cells with liquid nitrogen to obtain high cooling rates, which however causes the potential contamination and difficult cell collection. To address these limitations, we developed a non-contact vitrification device based on an ultra-thin freezing film to achieve high cooling/warming rate and avoid direct contact between cells and liquid nitrogen. A high-throughput cell printer was employed to rapidly generate uniform cell-laden microdroplets into the device, where the microdroplets were hung on one side of the film and then vitrified by pouring the liquid nitrogen onto the other side via boiling heat transfer. Through theoretical and experimental studies on vitrification processes, we demonstrated that our device offers a high cooling/warming rate for vitrification of the NIH 3T3 cells and human adipose-derived stem cells (hASCs) with maintained cell viability and differentiation potential. This non-contact vitrification device provides a novel and effective way to cryopreserve cells at high throughput and avoid the contamination and collection problems.
  18. Qi H, Huang G, Han Y, Zhang X, Li Y, Pingguan-Murphy B, et al.
    Tissue Eng Part B Rev, 2015 Jun;21(3):288-97.
    PMID: 25547514 DOI: 10.1089/ten.TEB.2014.0494
    Deoxyribonucleic acid (DNA) emerges as building bricks for the fabrication of nanostructure with complete artificial architecture and geometry. The amazing ability of DNA in building two- and three-dimensional structures raises the possibility of developing smart nanomachines with versatile controllability for various applications. Here, we overviewed the recent progresses in engineering DNA machines for specific bioengineering and biomedical applications.
  19. Hong YH, Frugier T, Zhang X, Murphy RM, Lynch GS, Betik AC, et al.
    J. Appl. Physiol., 2015 May 1;118(9):1113-21.
    PMID: 25749441 DOI: 10.1152/japplphysiol.00056.2015
    Inhibition of nitric oxide synthase (NOS) significantly attenuates the increase in skeletal muscle glucose uptake during contraction/exercise, and a greater attenuation is observed in individuals with Type 2 diabetes compared with healthy individuals. Therefore, NO appears to play an important role in mediating muscle glucose uptake during contraction. In this study, we investigated the involvement of neuronal NOSμ (nNOSμ), the main NOS isoform activated during contraction, on skeletal muscle glucose uptake during ex vivo contraction. Extensor digitorum longus muscles were isolated from nNOSμ(-/-) and nNOSμ(+/+) mice. Muscles were contracted ex vivo in a temperature-controlled (30°C) organ bath with or without the presence of the NOS inhibitor N(G)-monomethyl-l-arginine (L-NMMA) and the NOS substrate L-arginine. Glucose uptake was determined by radioactive tracers. Skeletal muscle glucose uptake increased approximately fourfold during contraction in muscles from both nNOSμ(-/-) and nNOSμ(+/+) mice. L-NMMA significantly attenuated the increase in muscle glucose uptake during contraction in both genotypes. This attenuation was reversed by L-arginine, suggesting that L-NMMA attenuated the increase in muscle glucose uptake during contraction by inhibiting NOS and not via a nonspecific effect of the inhibitor. Low levels of NOS activity (~4%) were detected in muscles from nNOSμ(-/-) mice, and there was no evidence of compensation from other NOS isoform or AMP-activated protein kinase which is also involved in mediating muscle glucose uptake during contraction. These results indicate that NO regulates skeletal muscle glucose uptake during ex vivo contraction independently of nNOSμ.
  20. Zhang X, Kadir KA, Quintanilla-Zariñan LF, Villano J, Houghton P, Du H, et al.
    Malar. J., 2016 09 02;15(1):450.
    PMID: 27590474 DOI: 10.1186/s12936-016-1494-0
    BACKGROUND: Plasmodium knowlesi and Plasmodium cynomolgi are two malaria parasites naturally transmissible between humans and wild macaque through mosquito vectors, while Plasmodium inui can be experimentally transmitted from macaques to humans. One of their major natural hosts, the long-tailed macaque (Macaca fascicularis), is host to two other species of Plasmodium (Plasmodium fieldi and Plasmodium coatneyi) and is widely distributed in Southeast Asia. This study aims to determine the distribution of wild macaques infected with malarial parasites by examining samples derived from seven populations in five countries across Southeast Asia.

    METHODS: Plasmodium knowlesi, P. cynomolgi, P. coatneyi, P. inui and P. fieldi, were detected using nested PCR assays in DNA samples from 276 wild-caught long-tailed macaques. These samples had been derived from macaques captured at seven locations, two each in the Philippines (n = 68) and Indonesia (n = 70), and one each in Cambodia (n = 54), Singapore (n = 40) and Laos (n = 44). The results were compared with previous studies of malaria parasites in long-tailed macaques from other locations in Southeast Asia. Fisher exact test and Chi square test were used to examine the geographic bias of the distribution of Plasmodium species in the macaque populations.

    RESULTS: Out of 276 samples tested, 177 were Plasmodium-positive, with P. cynomolgi being the most common and widely distributed among all long-tailed macaque populations (53.3 %) and occurring in all populations examined, followed by P. coatneyi (20.4 %), P. inui (12.3 %), P. fieldi (3.4 %) and P. knowlesi (0.4 %). One P. knowlesi infection was detected in a macaque from Laos, representing the first documented case of P. knowlesi in wildlife in Laos. Chi square test showed three of the five parasites (P. knowlesi, P. coatneyi, P. cynomolgi) with significant bias in prevalence towards macaques from Malaysian Borneo, Cambodia, and Southern Sumatra, respectively.

    CONCLUSIONS: The prevalence of malaria parasites, including those that are transmissible to humans, varied among all sampled regional populations of long-tailed macaques in Southeast Asia. The new discovery of P. knowlesi infection in Laos, and the high prevalence of P. cynomolgi infections in wild macaques in general, indicate the strong need of public advocacy in related countries.

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