Displaying publications 41 - 60 of 220 in total

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  1. Cheong FW, Dzul S, Fong MY, Lau YL, Ponnampalavanar S
    Acta Trop, 2020 Jun;206:105454.
    PMID: 32205132 DOI: 10.1016/j.actatropica.2020.105454
    Transmission of Plasmodium vivax still persist in Malaysia despite the government's aim to eliminate malaria in 2020. High treatment failure rate of chloroquine monotherapy was reported recently. Hence, parasite drug susceptibility should be kept under close monitoring. Mutation analysis of the drug resistance markers is useful for reconnaissance of anti-malarial drug resistance. Hitherto, information on P. vivax drug resistance marker in Malaysia are limited. This study aims to evaluate the mutations in four P. vivax drug resistance markers pvcrt-o (putative), pvmdr1 (putative), pvdhfr and pvdhps in 44 isolates from Malaysia. Finding indicates that 27.3%, 100%, 47.7%, and 27.3% of the isolates were carrying mutant allele in pvcrt-o, pvmdr1, pvdhfr and pvdhps genes, respectively. Most of the mutant isolates had multiple point mutations rather than single point mutation in pvmdr1 (41/44) and pvdhfr (19/21). One novel point mutation V111I was detected in pvdhfr. Allelic combination analysis shows significant strong association between mutations in pvcrt-o and pvmdr1 (X2 = 9.521, P < 0.05). In the present study, 65.9% of the patients are non-Malaysians, with few of them arrived in Malaysia 1-2 weeks before the onset of clinical manifestations, or had previous history of malaria infection. Besides, few Malaysian patients had travel history to vivax-endemic countries, suggesting that these patients might have acquired the infections during their travel. All these possible imported cases could have placed Malaysia in a risk to have local transmission or outbreak of malaria. Six isolates were found to have mutations in all four drug resistance markers, suggesting that the multiple-drugs resistant P. vivax strains are circulating in Malaysia.
  2. Li LF, Pusadee T, Wedger MJ, Li YL, Li MR, Lau YL, et al.
    Nat Commun, 2024 Feb 21;15(1):1182.
    PMID: 38383554 DOI: 10.1038/s41467-024-45447-0
    High reproductive compatibility between crops and their wild relatives can provide benefits for crop breeding but also poses risks for agricultural weed evolution. Weedy rice is a feral relative of rice that infests paddies and causes severe crop losses worldwide. In regions of tropical Asia where the wild progenitor of rice occurs, weedy rice could be influenced by hybridization with the wild species. Genomic analysis of this phenomenon has been very limited. Here we use whole genome sequence analyses of 217 wild, weedy and cultivated rice samples to show that wild rice hybridization has contributed substantially to the evolution of Southeast Asian weedy rice, with some strains acquiring weed-adaptive traits through introgression from the wild progenitor. Our study highlights how adaptive introgression from wild species can contribute to agricultural weed evolution, and it provides a case study of parallel evolution of weediness in independently-evolved strains of a weedy crop relative.
  3. Onichandran S, Kumar T, Salibay CC, Dungca JZ, Tabo HA, Tabo N, et al.
    Parasit Vectors, 2014;7:244.
    PMID: 24885105 DOI: 10.1186/1756-3305-7-244
    Despite the amount of awareness created, waterborne disease still poses threat, especially in developing countries. Due to the scarcity of reported data on waterborne parasites, the consumption of unsafe water prolongs. Thus, the occurrences of waterborne parasites from various samples were investigated from one of the Southeast Asian country, the Philippines.
  4. Ching XT, Lau YL, Fong MY, Nissapatorn V
    Parasitol Res, 2013 Mar;112(3):1229-36.
    PMID: 23274488 DOI: 10.1007/s00436-012-3255-5
    Toxoplasma gondii infects all warm-blooded animals including humans, causing serious public health problems and great economic loss in the food industry. Commonly used serological tests involve preparation of whole Toxoplasma lysate antigens from tachyzoites which are costly and hazardous. An alternative method for better antigen production involving the prokaryotic expression system was therefore used in this study. Recombinant dense granular protein, GRA2, was successfully cloned, expressed, and purified in Escherichia coli, BL21 (DE3) pLysS. The potential of this purified antigen for diagnosis of human infections was evaluated through western blot analysis against 100 human serum samples. Results showed that the rGRA2 protein has 100 and 61.5 % sensitivity towards acute and chronic infection, respectively, in T. gondii-infected humans, indicating that this protein is useful in differentiating present and past infections. Therefore, it is suitable to be used as a sensitive and specific molecular marker for the serodiagnosis of Toxoplasma infection in both humans and animals.
  5. Init I, Lau YL, Arin Fadzlun A, Foead AI, Neilson RS, Nissapatorn V
    Trop Biomed, 2010 Dec;27(3):566-77.
    PMID: 21399599 MyJurnal
    This study reports the detection of Acanthamoeba and Naegleria species in 14 swimming pools around Petaling Jaya and Kuala Lumpur, Malaysia. Sampling was carried out at 4 sites (the platforms (P), wall (W), 1 meter from the wall (1) and middle (2)) of each swimming pool. These free living amoebae (FLA) were detected under light and inverted microscopes after being cultured on the surface of non-nutrient agar lawned with Escherichia coli. Acanthamoeba species were detected in higher number of culture plates from all sampling sites of all the swimming pools. While Naegleria, were detected in fewer culture plates at 3 sampling sites (absent at site P) of 8 swimming pools. This suggested that the thick double-walled cysts of Acanthamoeba were more resistant, thus remaining viable in the dry-hot areas of the platforms and in chlorinated water of the swimming pools whereas Naegleria cysts, that are fragile and susceptible to desiccation, preferred watery or moist areas for growth and proliferation. The prevalence of both FLA was highest at site W (76.2%), followed by site 1 (64.7%), lowest at site 2 (19.4%), and could be detected at all 3 sampling levels (top, middle and bottom) of these 3 sites. The surface of site W might act as a bio-film that accumulated all kinds of microbes providing sufficient requirement for the FLA to develop and undergo many rounds of life cycles as well as moving from top to bottom in order to graze food. Other factors such as human activities, the circulating system which was fixed at all swimming pools, blowing wind which might carry the cysts from surroundings and the swimming flagellate stage of Naegleria could also contribute to the distribution of the FLA at these sampling sites. Both FLA showed highest growth (80.4%) at room temperature (25-28 ºC) and lesser (70.0%) at 37 ºC which might be due to the overgrowth of other microbes (E. coli, fungi, algae, etc). While at 44 ºC, only Acanthamoeba species could survive thus showing that our swimming pools are free from potentially pathogenic Naegleria species. However, further study is needed in order to confirm the virulence levels of these amoebae isolates.
  6. Molineros JE, Yang W, Zhou XJ, Sun C, Okada Y, Zhang H, et al.
    Hum Mol Genet, 2017 03 15;26(6):1205-1216.
    PMID: 28108556 DOI: 10.1093/hmg/ddx026
    We recently identified ten novel SLE susceptibility loci in Asians and uncovered several additional suggestive loci requiring further validation. This study aimed to replicate five of these suggestive loci in a Han Chinese cohort from Hong Kong, followed by meta-analysis (11,656 cases and 23,968 controls) on previously reported Asian and European populations, and to perform bioinformatic analyses on all 82 reported SLE loci to identify shared regulatory signatures. We performed a battery of analyses for these five loci, as well as joint analyses on all 82 SLE loci. All five loci passed genome-wide significance: MYNN (rs10936599, Pmeta = 1.92 × 10-13, OR = 1.14), ATG16L2 (rs11235604, Pmeta = 8.87 × 10 -12, OR = 0.78), CCL22 (rs223881, Pmeta = 5.87 × 10-16, OR = 0.87), ANKS1A (rs2762340, Pmeta = 4.93 × 10-15, OR = 0.87) and RNASEH2C (rs1308020, Pmeta = 2.96 × 10-19, OR = 0.84) and co-located with annotated gene regulatory elements. The novel loci share genetic signatures with other reported SLE loci, including effects on gene expression, transcription factor binding, and epigenetic characteristics. Most (56%) of the correlated (r2 > 0.8) SNPs from the 82 SLE loci were implicated in differential expression (9.81 × 10-198 
  7. Shearer FM, Huang Z, Weiss DJ, Wiebe A, Gibson HS, Battle KE, et al.
    PLoS Negl Trop Dis, 2016 Aug;10(8):e0004915.
    PMID: 27494405 DOI: 10.1371/journal.pntd.0004915
    BACKGROUND: Infection by the simian malaria parasite, Plasmodium knowlesi, can lead to severe and fatal disease in humans, and is the most common cause of malaria in parts of Malaysia. Despite being a serious public health concern, the geographical distribution of P. knowlesi malaria risk is poorly understood because the parasite is often misidentified as one of the human malarias. Human cases have been confirmed in at least nine Southeast Asian countries, many of which are making progress towards eliminating the human malarias. Understanding the geographical distribution of P. knowlesi is important for identifying areas where malaria transmission will continue after the human malarias have been eliminated.

    METHODOLOGY/PRINCIPAL FINDINGS: A total of 439 records of P. knowlesi infections in humans, macaque reservoir and vector species were collated. To predict spatial variation in disease risk, a model was fitted using records from countries where the infection data coverage is high. Predictions were then made throughout Southeast Asia, including regions where infection data are sparse. The resulting map predicts areas of high risk for P. knowlesi infection in a number of countries that are forecast to be malaria-free by 2025 (Malaysia, Cambodia, Thailand and Vietnam) as well as countries projected to be eliminating malaria (Myanmar, Laos, Indonesia and the Philippines).

    CONCLUSIONS/SIGNIFICANCE: We have produced the first map of P. knowlesi malaria risk, at a fine-scale resolution, to identify priority areas for surveillance based on regions with sparse data and high estimated risk. Our map provides an initial evidence base to better understand the spatial distribution of this disease and its potential wider contribution to malaria incidence. Considering malaria elimination goals, areas for prioritised surveillance are identified.

  8. Mohd Hanapi IR, Sahimin N, Lewis JW, Lau YL, Othman J, Tedong PA, et al.
    Trop Biomed, 2021 Dec 01;38(4):594-604.
    PMID: 35001926 DOI: 10.47665/tb.38.4.103
    The United Nations High Commissioner for Refugees (UNHCR) reports over 80 million people are displaced worldwide with approximately 26.3 million categorized as refugees and over a million residing temporarily in South East Asia. Despite the lack of national legislative framework in place for refugees and asylum seekers (RAS), Malaysia hosts approximately 178,140 as registered with UNHCR and the majority originate from Myanmar. In this review, we examine refugees from South East Asia, particularly from Myanmar that have contributed to the largest influx of refugees to this region with a focus on their health status. The present study traces barriers to the health care of refugees in the country of asylum and also the challenges faced by these communities in accessing health services.
  9. Mohd Hanapi IR, Sahimin N, Maackara MJB, Annisa AS, Abdul Mutalib RNS, Lewis JW, et al.
    BMC Infect Dis, 2021 Nov 01;21(1):1128.
    PMID: 34724919 DOI: 10.1186/s12879-021-06830-0
    BACKGROUND: Refugees in Malaysia, who are afflicted by poverty, conflict and poor health, are vulnerable to a range of zoonotic infections in the deprived environmental and social conditions under which they live. Exposure to infections such as leptospirosis, for which rodents are primary hosts, is of particular concern.

    METHODS: A wellness program was conducted to determine the presence of antibodies against Leptospira (seroprevalence) in 11 refugee community schools and centers in the Klang Valley, Malaysia. A total of 433 samples were assessed for IgG and IgM antibodies against Leptospira, using enzyme-linked immunosorbent assays (ELISA).

    RESULTS: Overall Leptospira seroprevalence was 24.7%, with 3.0% being seropositive for anti-Leptospira IgG and 21.7% for anti-Leptospira IgM. Factors significantly associated with overall Leptospira seroprevalence included: age, ethnicity, pet ownership, knowledge of disease and awareness of disease fatality. For IgM seroprevalence, significant risk factors included sex, ethnicity, eating habits with hands, pet ownership, the presence of rats, walking in bare feet and water recreation visits.

    CONCLUSIONS: These findings highlight the need for improvements in health and well-being among the refugee community through disease awareness programs and provision of healthy behavior programs, particularly in hygiene and sanitation through community engagement activities.

  10. Mohd Hanapi IR, Behnke JM, Sahimin N, Saifulazmi NF, Golam Mohammad Khan ASJ, Abdul Mutalib RNS, et al.
    Trans R Soc Trop Med Hyg, 2024 Jan 02;118(1):18-32.
    PMID: 37497742 DOI: 10.1093/trstmh/trad047
    BACKGROUND: Global studies show intestinal parasitic infections (IPIs) have been introduced and spread with refugee inflows from low to high socio-economic countries. However, there is relatively limited information on the prevalence of infections among the community.

    METHODS: A 2-year cross-sectional study was conducted to determine the prevalence and associated risk factors for infections among urban refugees in the Klang Valley, Malaysia. A total of 418 faecal samples were collected and examined by microscopy.

    RESULTS: Faecal screening revealed moderate levels (32.3%) of infections in the community. Three nematode (Ascaris lumbricoides, Trichuris trichiura and hookworm) and three protozoan species (Entamoeba, Giardia and Cryptosporidium) were recorded, with the highest prevalence being A. lumbricoides (20.6%) followed by T. trichiura (10.3%), while other infections were <5%. Statistical analysis found that young males with less education were more likely to be infected with helminths. Additionally, living near waste disposal sites, the presence of stray animals, eating with bare hands, bare footedness, poor handwashing practices and no anthelmintic treatment constituted significant risk factors for helminth infections. Protozoan infections were linked to drinking tap water or from water dispensers and poor handwashing practices.

    CONCLUSIONS: These findings emphasize the importance of health education in addition to introduction of biannual anthelmintic treatment to promote community health and well-being.

  11. Yusof R, Lau YL, Mahmud R, Fong MY, Jelip J, Ngian HU, et al.
    Malar J, 2014;13:168.
    PMID: 24886266 DOI: 10.1186/1475-2875-13-168
    Plasmodium knowlesi is a simian parasite that has been recognized as the fifth species causing human malaria. Naturally-acquired P. knowlesi infection is widespread among human populations in Southeast Asia. The aim of this epidemiological study was to determine the incidence and distribution of malaria parasites, with a particular focus on human P. knowlesi infection in Malaysia.
  12. van Enter BJD, Lau YL, Ling CL, Watthanaworawit W, Sukthana Y, Lee WC, et al.
    Am J Trop Med Hyg, 2017 Jul;97(1):232-235.
    PMID: 28719309 DOI: 10.4269/ajtmh.16-0999
    Toxoplasma gondii primary infection in pregnancy is associated with poor obstetric outcomes. This study aimed to determine the seroprevalence of Toxoplasma infection in pregnant migrant and refugee women from Myanmar attending antenatal care in Thailand. A random selection of 199 residual blood samples from first antenatal screen in 2014-2015 was tested for Toxoplasma IgG and IgM antibodies. Seroprevalence of Toxoplasma infection was 31.7% (95% confidence interval = 25.6-38.4). Avidity testing in the three positive IgM cases indicated all were past infections. Multiparity (≥ 3 children) was significantly associated with higher Toxoplasma seropositivity rates. Seroprevalence of T. gondii infection in this pregnant population is similar to the only other report from Myanmar, where multiparity was also identified as a significant association. Toxoplasma infection is important in pregnant women. Nevertheless, in this marginalized population, this infection may be given less priority, due to resource constraints in providing the most basic components of safe motherhood programs.
  13. Andiappan H, Nissapatorn V, Sawangjaroen N, Khaing SL, Salibay CC, Cheung MM, et al.
    Front Microbiol, 2014;5:291.
    PMID: 24966855 DOI: 10.3389/fmicb.2014.00291
    Toxoplasma gondii, is one of the infectious agents of congenital TORCH infections, causes severe clinical outcomes in fetus and newborns. Nevertheless this life-threatening parasitic disease is preventable by simple preventive measures related to lifestyle during pregnancy. We aim to study on the knowledge about toxoplasmosis and practices that prevents this infection among the pregnant women. Total of 2598 pregnant women from Malaysia, Philippines, and Thailand were randomly surveyed to determine the knowledge and their practices on Toxoplasma infection. The questionnaire covered respondents' general information and knowledge on plausible risks factors, symptoms, timing of infection, prevention knowledge, and preventive behavior regarding Toxoplasma infection. Majority of these pregnant women were in their age group of 20-29 years (50.9%), completed secondary level of education (51.7%), in their second trimester of pregnancies (38.1%), non-parous (36.6%), and had no history of abortion (90.4%). Based on this survey, only 11% of these pregnant women had read, heard, or seen information regarding toxoplasmosis and 3.5% of them were aware of being tested for the infection. A small percentage of these pregnant women knew that T. gondii were shed in the feces of infected cats (19.4%) and sometimes found in the raw or undercooked meat (11.0%). There was 16.1% of responding women knew that toxoplasmosis is caused by an infection. Demographic profiles such as age group, level of education, pregnancy term, and number of children of the pregnant women showed significant association with their responses toward prevention knowledge and preventive behavior related questions (P < 0.05). Thus, it is suggested that health education on toxoplasmosis and primary behavioral practices should be consistently offered to reproductive age women in general and pregnant women in particular. This information could help to reduce vertical transmission of Toxoplasma infection during pregnancy.
  14. Ithoi I, Ahmad AF, Nissapatorn V, Lau YL, Mahmud R, Mak JW
    PLoS One, 2011;6(9):e24327.
    PMID: 21915311 DOI: 10.1371/journal.pone.0024327
    BACKGROUND: In Malaysia, researchers and medical practitioners are unfamiliar with Naegleria infections. Thus little is known about the existence of pathogenic Naegleria fowleri, and the resultant primary amoebic meningoencephalitis (PAM) is seldom included in the differential diagnosis of central nervous system infections. This study was conducted to detect the presence of Naegleria species in various environmental samples.

    METHODS/FINDINGS: A total of 41 Naegleria-like isolates were isolated from water and dust samples. All these isolates were subjected to PCR using two primer sets designed from the ITS1-ITS2 regions. The N. fowleri species-specific primer set failed to produce the expected amplicon. The Naegleria genus-specific primers produced amplicons of 408 bp (35), 450 bp (2), 457 bp (2) or 381 bp (2) from all 41 isolates isolated from aquatic (33) and dust (8) samples. Analysis of the sequences from 10 representative isolates revealed that amplicons with fragments 408, 450 and 457 bp showed homology with non-pathogenic Naegleria species, and 381 bp showed homology with Vahlkampfia species. These results concurred with the morphological observation that all 39 isolates which exhibited flagella were Naegleria, while 2 isolates (AC7, JN034055 and AC8, JN034056) that did not exhibit flagella were Vahlkampfia species.

    CONCLUSION: To date, pathogenic species of N. fowleri have not been isolated from Malaysia. All 39 isolates that produced amplicons (408, 450 and 457 bp) from the genus-specific primers were identified as being similar to nonpathogenic Naegleria. Amplicon 408 bp from 5 representative isolates showed 100% and 99.7% identity to Naegleria philippinensis isolate RJTM (AM167890) and is thus believed to be the most common species in our environment. Amplicons 450 bp and 457 bp were respectively believed to be from 2 new species of Naegleria, since representative isolates showed lower homology and had a longer base pair length when compared to the reference species in the Genbank, Naegleria schusteri (AJ566626) and Naegleria laresi (AJ566630), respectively.

  15. Amir A, Ngui R, Ismail WH, Wong KT, Ong JS, Lim YA, et al.
    Am J Trop Med Hyg, 2016 Aug 03;95(2):410-2.
    PMID: 27325803 DOI: 10.4269/ajtmh.16-0007
    Human anisakiasis is a zoonosis acquired by eating raw or undercooked infected seafood. Herein, we report a case of acute dysentery caused by anisakiasis in a 64-year-old man in Malaysia. A colonoscopy was performed and a nematode larva was found penetrating the mucosa of the ascending colon. Bleeding was observed at the site of penetration. Y-shaped lateral epidermal cords were seen from the cross section of the worm, which is a prominent feature of Anisakis larva. Molecular analysis using polymerase chain reaction of cytochrome oxidase 2 (cox2) gene confirmed the specimen to be larva of Anisakis simplex.
  16. Lau YL, Lai MY, Fong MY, Jelip J, Mahmud R
    Am J Trop Med Hyg, 2016 Feb;94(2):336-339.
    PMID: 26598573 DOI: 10.4269/ajtmh.15-0569
    The lack of rapid, affordable, and accurate diagnostic tests represents the primary hurdle affecting malaria surveillance in resource- and expertise-limited areas. Loop-mediated isothermal amplification (LAMP) is a sensitive, rapid, and cheap diagnostic method. Five species-specific LAMP assays were developed based on 18S rRNA gene. Sensitivity and specificity of LAMP results were calculated as compared with microscopic examination and nested polymerase chain reaction. LAMP reactions were highly sensitive with the detection limit of one copy for Plasmodium vivax, Plasmodium falciparum, and Plasmodium malariae and 10 copies for Plasmodium knowlesi and Plasmodium ovale. LAMP positively detected all human malaria species in all positive samples (N = 134; sensitivity = 100%) within 35 minutes. All negative samples were not amplified by LAMP (N = 67; specificity = 100%). LAMP successfully detected two samples with very low parasitemia. LAMP may offer a rapid, simple, and reliable test for the diagnosis of malaria in areas where malaria is prevalent.
  17. Lau YL, Lai MY, Anthony CN, Chang PY, Palaeya V, Fong MY, et al.
    Am J Trop Med Hyg, 2015 Jan;92(1):28-33.
    PMID: 25385862 DOI: 10.4269/ajtmh.14-0309
    In this study, three molecular assays (real-time multiplex polymerase chain reaction [PCR], merozoite surface antigen gene [MSP]-multiplex PCR, and the PlasmoNex Multiplex PCR Kit) have been developed for diagnosis of Plasmodium species. In total, 52 microscopy-positive and 20 malaria-negative samples were used in this study. We found that real-time multiplex PCR was the most sensitive for detecting P. falciparum and P. knowlesi. The MSP-multiplex PCR assay and the PlasmoNex Multiplex PCR Kit were equally sensitive for diagnosing P. knowlesi infection, whereas the PlasmoNex Multiplex PCR Kit and real-time multiplex PCR showed similar sensitivity for detecting P. vivax. The three molecular assays displayed 100% specificity for detecting malaria samples. We observed no significant differences between MSP-multiplex PCR and the PlasmoNex multiplex PCR kit (McNemar's test: P = 0.1489). However, significant differences were observed comparing real-time multiplex PCR with the PlasmoNex Multiplex PCR Kit (McNemar's test: P = 0.0044) or real-time multiplex PCR with MSP-multiplex PCR (McNemar's test: P = 0.0012).
  18. Cheong FW, Fong MY, Lau YL, Mahmud R
    Malar J, 2013;12:454.
    PMID: 24354660 DOI: 10.1186/1475-2875-12-454
    Plasmodium knowlesi is the fifth Plasmodium species that can infect humans. The Plasmodium merozoite surface protein-1(42) (MSP-1(42)) is a potential candidate for malaria vaccine. However, limited studies have focused on P. knowlesi MSP-1(42).
  19. Anthony CN, Lau YL, Sum JS, Fong MY, Ariffin H, Zaw WL, et al.
    Malar J, 2013;12:308.
    PMID: 24007496 DOI: 10.1186/1475-2875-12-308
    Malaria may be a serious complication of blood transfusion due to the asymptomatic persistence of parasites in some donors. This case report highlights the transfusion-transmitted malaria of Plasmodium vivax in a child diagnosed with germ cell tumour. This child had received blood transfusion from three donors and a week later started developing malaria like symptoms. Nested PCR and sequencing confirmed that one of the three donors was infected with P. vivax and this was transmitted to the 12-year-old child. To the best of the authors' knowledge, this is the first reported transfusion-transmitted malaria case in Malaysia.
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