Displaying publications 1 - 20 of 173 in total

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  1. Shepard DS, Undurraga EA, Lees RS, Halasa Y, Lum LCS, Ng CW
    Am. J. Trop. Med. Hyg., 2012 Nov;87(5):796-805.
    PMID: 23033404 DOI: 10.4269/ajtmh.2012.12-0019
    Dengue represents a substantial burden in many tropical and sub-tropical regions of the world. We estimated the economic burden of dengue illness in Malaysia. Information about economic burden is needed for setting health policy priorities, but accurate estimation is difficult because of incomplete data. We overcame this limitation by merging multiple data sources to refine our estimates, including an extensive literature review, discussion with experts, review of data from health and surveillance systems, and implementation of a Delphi process. Because Malaysia has a passive surveillance system, the number of dengue cases is under-reported. Using an adjusted estimate of total dengue cases, we estimated an economic burden of dengue illness of US$56 million (Malaysian Ringgit MYR196 million) per year, which is approximately US$2.03 (Malaysian Ringgit 7.14) per capita. The overall economic burden of dengue would be even higher if we included costs associated with dengue prevention and control, dengue surveillance, and long-term sequelae of dengue.
  2. Appanna R, Wang SM, Ponnampalavanar SA, Lum LC, Sekaran SD
    Am. J. Trop. Med. Hyg., 2012 Nov;87(5):936-42.
    PMID: 22987650 DOI: 10.4269/ajtmh.2012.11-0606
    Plasma leakage in severe dengue has been postulated to be associated with skewed cytokine immune responses. In this study, the association of cytokines with vascular permeability in dengue patients was investigated. Human serum samples collected from 48 persons (13 with dengue fever, 29 with dengue hemorrhagic fever, and 6 healthy) were subjected to cytokines analysis by using Luminex Multiplex Technology. Selected serum samples from patients with dengue hemorrhagic fever sera and recombinant human cytokines were then tested for roles on inducing vascular permeability by treatment of human umbilical vein endothelial cells. Confocal immunofluorescence staining indicated morphologic alteration of human umbilical vein endothelial cells treated with serum samples from patients with dengue hemorrhagic fever compared with serum samples from healthy persons. The findings suggest that cytokines produced during dengue hemorrhagic infections could induce alterations in the vascular endothelium, which may play a fundamental role in the pathophysiology of dengue.
  3. Benacer D, Mohd Zain SN, Amran F, Galloway RL, Thong KL
    Am. J. Trop. Med. Hyg., 2013 Apr;88(4):704-9.
    PMID: 23358635 DOI: 10.4269/ajtmh.12-0662
    Rats are considered the principal maintenance hosts of Leptospira. The objectives of this study were isolation and identification of Leptospira serovars circulating among urban rat populations in Kuala Lumpur. Three hundred urban rats (73% Rattus rattus and 27% R. norvegicus) from three different sites were trapped. Twenty cultures were positive for Leptospira using dark-field microscopy. R. rattus was the dominant carrier (70%). Polymerase chain reaction (PCR) confirmed that all isolates were pathogenic Leptospira species. Two Leptospira serogroups, Javanica and Bataviae, were identified using microscopic agglutination test (MAT). Pulsed-field gel electrophoresis (PFGE) identified two serovars in the urban rat populations: L. borgpetersenii serovar Javanica (85%) and L. interrogans serovar Bataviae (15%). We conclude that these two serovars are the major serovars circulating among the urban rat populations in Kuala Lumpur. Despite the low infection rate reported, the high pathogenicity of these serovars raises concern of public health risks caused by rodent transmission of leptospirosis.
  4. Hin HS, Ramalingam R, Chunn KY, Ahmad N, Ab Rahman J, Mohamed MS
    Am. J. Trop. Med. Hyg., 2012 Oct;87(4):737-40.
    PMID: 22826499 DOI: 10.4269/ajtmh.2012.12-0165
    Co-infection of melioidosis and leptospirosis is uncommon. We report here four such cases, confirmed by blood culture for melioidosis and blood polymerase-chain reaction for leptospirosis, which occurred among rescuers involved in a search and rescue operation for a young man who was suspected to have drowned in Lubuk Yu, a recreational forest in Pahang, Malaysia. Despite treatment, three of the patients died from the co-infection.
  5. Ng LC, Chem YK, Koo C, Mudin RNB, Amin FM, Lee KS, et al.
    Am. J. Trop. Med. Hyg., 2015 Jun;92(6):1150-1155.
    PMID: 25846296 DOI: 10.4269/ajtmh.14-0588
    Characterization of 14,079 circulating dengue viruses in a cross-border surveillance program, UNITEDengue, revealed that the 2013 outbreaks in Singapore and Malaysia were associated with replacement of predominant serotype. While the predominant virus in Singapore switched from DENV2 to DENV1, DENV2 became predominant in neighboring Malaysia. Dominance of DENV2 was most evident on the southern states where higher fatality rates were observed.
  6. Chook JB, Ong LY, Takebe Y, Chan KG, Choo M, Kamarulzaman A, et al.
    Am. J. Trop. Med. Hyg., 2015 Mar;92(3):507-512.
    PMID: 25535315 DOI: 10.4269/ajtmh.14-0681
    A molecular genotyping assay for human immunodeficiency virus type 1 (HIV-1) circulating in Southeast Asia is difficult to design because of the high level of genetic diversity. We developed a multiplex real-time polymerase chain reaction (PCR) assay to detect subtype B, CRF01_AE, CRF33_01B, and three newly described circulating recombinant forms, (CRFs) (CRF53_01B, CRF54_01B, and CRF58_01B). A total of 785 reference genomes were used for subtype-specific primers and TaqMan probes design targeting the gag, pol, and env genes. The performance of this assay was compared and evaluated with direct sequencing and phylogenetic analysis. A total of 180 HIV-infected subjects from Kuala Lumpur, Malaysia were screened and 171 samples were successfully genotyped, in agreement with the phylogenetic data. The HIV-1 genotype distribution was as follows: subtype B (16.7%); CRF01_AE (52.8%); CRF33_01B (24.4%); CRF53_01B (1.1%); CRF54_01B (0.6%); and CRF01_AE/B unique recombinant forms (4.4%). The overall accuracy of the genotyping assay was over 95.0%, in which the sensitivities for subtype B, CRF01_AE, and CRF33_01B detection were 100%, 100%, and 97.7%, respectively. The specificity of genotyping was 100%, inter-subtype specificities were > 95% and the limit of detection of 10(3) copies/mL for plasma. The newly developed real-time PCR assay offers a rapid and cost-effective alternative for large-scale molecular epidemiological surveillance for HIV-1.
  7. Ngui R, Ching LS, Kai TT, Roslan MA, Lim YA
    Am. J. Trop. Med. Hyg., 2012 May;86(5):837-42.
    PMID: 22556084 DOI: 10.4269/ajtmh.2012.11-0446
    Species identification of human hookworm infections among eight communities in rural areas of Peninsular Malaysia was determined during 2009-2011. Fecal samples were examined by microscopy and subsequently, the internal transcribed spacer 2 and 28S ribosomal RNA region of Necator americanus and Ancylostoma spp. were sequenced. Overall, 9.1% (58 of 634) were identified positive by microscopy for hookworm infection, and 47 (81.0%) of 58 were successfully amplified and sequenced. Sequence comparison found that N. americanus (87.2%) was the most predominant hookworm identified, followed by Ancylostoma ceylanicum (23.4%). No A. duodenale infection was detected in this study. Detection of A. ceylanicum in humans highlighted the zoonotic transmission among humans living near dogs. Thus, implementation of effective control measures for hookworm infections in future should seriously consider this zoonotic implication.
  8. Mokhtar AS, Tay ST
    Am. J. Trop. Med. Hyg., 2011 Nov;85(5):931-3.
    PMID: 22049052 DOI: 10.4269/ajtmh.2011.10-0634
    The presence of Rickettsia felis, Bartonella henselae and B. clarridgeiae in 209 fleas (Ctenocephalides felis) obtained from domestic cats and dogs in several locations in Malaysia was investigated in this study. Using a polymerase chain reaction specific for the citrate synthase (gltA) and 17-kD antigenic protein (17kD) genes of rickettsiae, we detected R. felis DNA in 6 (2.9%) fleas. For detection of bartonellae, amplification of the heme-binding protein (pap31) and riboflavin synthase (ribC) genes identified B. henselae and B. clarridgeiae DNA in 24 (11.5%) and 40 (19.1%) fleas, respectively. The DNA of B. henselae and B. clarridgeiae was detected in 10 (4.8%) fleas. Two B. henselae genogroups (Marseille and Houston-1) were detected in this study; genogroup Marseille (genotype Fizz) was found more often in the fleas. The findings in this study suggest fleas as potential vectors of rickettsioses and cat-scratch disease in this country.
  9. Latif B, Omar E, Heo CC, Othman N, Tappe D
    Am. J. Trop. Med. Hyg., 2011 Nov;85(5):878-81.
    PMID: 22049042 DOI: 10.4269/ajtmh.2011.11-0404
    We report a case of visceral pentastomiasis caused by Armillifer moniliformis in a 70-year-old aboriginal farmer from rural Malaysian Borneo. The patient complained of upper abdominal pain, jaundice, and loss of weight. Radiological investigations and subsequent histopathological examination revealed an adenocarcinoma of the pancreas with an adjacent liver nodule containing a nymph of A. moniliformis. This report constitutes the first documented human pentastomid infection in the whole of Malaysia after nearly 40 years, and it is the third description from Malaysian Borneo. Cases of human and animal pentastomiasis in Malaysia are discussed.
  10. Halpin K, Hyatt AD, Fogarty R, Middleton D, Bingham J, Epstein JH, et al.
    Am. J. Trop. Med. Hyg., 2011 Nov;85(5):946-51.
    PMID: 22049055 DOI: 10.4269/ajtmh.2011.10-0567
    Bats of the genus Pteropus have been identified as the reservoir hosts for the henipaviruses Hendra virus (HeV) and Nipah virus (NiV). The aim of these studies was to assess likely mechanisms for henipaviruses transmission from bats. In a series of experiments, Pteropus bats from Malaysia and Australia were inoculated with NiV and HeV, respectively, by natural routes of infection. Despite an intensive sampling strategy, no NiV was recovered from the Malaysian bats and HeV was reisolated from only one Australian bat; no disease was seen. These experiments suggest that opportunities for henipavirus transmission may be limited; therefore, the probability of a spillover event is low. For spillover to occur, a range of conditions and events must coincide. An alternate assessment framework is required if we are to fully understand how this reservoir host maintains and transmits not only these but all viruses with which it has been associated.
  11. Chang PY, Fong MY, Nissapatorn V, Lau YL
    Am. J. Trop. Med. Hyg., 2011 Sep;85(3):485-9.
    PMID: 21896809 DOI: 10.4269/ajtmh.2011.11-0351
    Rhoptry protein 2 (ROP2) of Toxoplasma gondii is a rhoptry-secreted protein that plays a critical role in parasitophorous vacuole membrane formation during invasion. In previous studies, ROP2 has been shown to be efficient in triggering humoral and cell-mediated responses. High immunogenicity of ROP2 makes it a potential candidate for diagnosis and vaccination against toxoplasmosis. In this study, the ROP2 gene was cloned into pPICZα A expression vector and extracellularly expressed in the yeast Pichia pastoris, which has numerous advantages over other expression systems for eukaryotic proteins expression. The effectiveness of the secreted recombinant ROP2 as a diagnosis agent was assessed by Western Blot with 200 human serum samples. Recombinant ROP2 reacted with toxoplasmosis-positive human serum samples and yielded an overall sensitivity of 90% and specificity of 95%. However, recombinant ROP2 is a better marker for detection of IgG (91.7%) rather than IgM (80%).
  12. Ngui R, Lim YA, Amir NF, Nissapatorn V, Mahmud R
    Am. J. Trop. Med. Hyg., 2011 Oct;85(4):660-6.
    PMID: 21976569 DOI: 10.4269/ajtmh.2011.11-0058
    This study aims to evaluate the current seroprevalence of toxoplasmosis among indigenous communities in Peninsular Malaysia and relate its association with epidemiological data. Overall seroprevalence of Toxoplasma gondii was 37.0% with 31.0% immunoglobulin (Ig) G, 1.8% IgM, and 4.2% seropositivity for both anti-Toxoplasma antibodies. Multivariate analysis showed that age above 12 years (odds ratio [OR] = 2.70, 95% confidence interval [CI] = 1.75-4.04, P < 0.001), using untreated river and mountain water supplies (OR = 1.50, 95% CI = 1.01-2.40, P = 0.050), and close proximity with cats (OR = 1.40, 95% CI = 1.10-1.76, P = 0.010) were factors associated with toxoplasmosis. Given the high seroprevalence of toxoplasmosis among these communities who live in poor socioeconomic conditions, a comprehensive health surveillance program and screening should be initiated among women of childbearing age and pregnant women during the antenatal period for early diagnosis and treatment. The role of domestic cats and environmental contamination with oocyst in soil and water has to be highlighted and addressed in future prevention strategies for these communities.
  13. Nissapatorn V, Suwanrath C, Sawangjaroen N, Ling LY, Chandeying V
    Am. J. Trop. Med. Hyg., 2011 Aug;85(2):243-7.
    PMID: 21813842 DOI: 10.4269/ajtmh.2011.10-0633
    Toxoplasma gondii is an important parasite in pregnant women. This case-controlled study assessed the seroprevalence of toxoplasmosis in 640 pregnant women in southern Thailand and identified their associated risk factors. The overall seroprevalence of toxoplasmosis was 181 (28.3%). Of this, 138 (21.6%) were positive for only anti-Toxoplasma immunoglobulin G (IgG) antibody, 43 (6.7%) were positive for both IgG and IgM antibodies, and none were positive for IgM antibody. Multivariate analysis revealed that increasing age (adjusted odds ratio [OR] = 1.64, 95% confidence interval [CI] = 1.01-2.67), living outside Songkhla province (adjusted OR = 1.56, 95% CI = 1.08-2.24), parity (adjusted OR = 1.65, 95% CI = 1.01-2.68), contact with cats (adjusted OR = 1.70, 95% CI = 1.20-2.43), and drinking of unclean water (adjusted OR = 1.70, 95% CI = 1.08-2.68) were factors associated with Toxoplasma seroprevalence. On the basis of the results obtained, a health surveillance program should be initiated as a primary preventive measure for congenital toxoplasmosis and focus on educating women of the child-bearing age group to avoid contact with cats and to strictly practice personal hygiene.
  14. Intapan PM, Chotmongkol V, Tantrawatpan C, Sanpool O, Morakote N, Maleewong W
    Am. J. Trop. Med. Hyg., 2011 Jun;84(6):994-7.
    PMID: 21633039 DOI: 10.4269/ajtmh.2011.10-0675
    Previously, we reported the presence of imported trichinellosis in a Thai worker returning from Malaysia, who presented with progressive generalized muscle hypertrophy and weakness after eating wild boar meat. This work analyzed a partial small subunit of a mitochondrial ribosomal RNA gene of Trichinella larvae isolated from the patient. The results showed complete identity with a mitochondrial RNA gene of Trichinella papuae (GenBank accession no. EF517130). This is the first report of imported trichinellosis in Thailand caused by T. papuae. It is possible that T. papuae is widely distributed in the wildlife of Southeast Asia.
  15. Ayu SM, Lai LR, Chan YF, Hatim A, Hairi NN, Ayob A, et al.
    Am. J. Trop. Med. Hyg., 2010 Dec;83(6):1245-8.
    PMID: 21118929 DOI: 10.4269/ajtmh.2010.10-0279
    In 2006, an outbreak of Chikungunya virus (CHIKV) of the Asian genotype affected over 200 people in Bagan Panchor village in Malaysia. One year later, a post-outbreak survey was performed to determine attack rate, asymptomatic rate, and post-infection sequelae. Findings were compared with recent CHIKV outbreaks of the Central/East African genotype. A total of 180 residents were interviewed for acute symptoms and post-infection physical quality of life and depressive symptoms. Sera from 72 residents were tested for CHIKV neutralizing antibodies. The estimated attack rate was 55.6%, and 17.5% of infected residents were asymptomatic. Arthralgia was reported up to 3 months after infection, but there were no reports of long-term functional dependence or depression. Symptomatic and seropositive residents were significantly more likely to live in the area with the most dense housing and commercial activities. CHIKV had a high attack rate and considerable clinical impact during the Bagan Panchor outbreak.
  16. Rahim AA, Lee YY, Majid NA, Choo KE, Raj SM, Derakhshan MH, et al.
    Am. J. Trop. Med. Hyg., 2010 Nov;83(5):1119-22.
    PMID: 21036849 DOI: 10.4269/ajtmh.2010.10-0226
    Whether the exceptionally low prevalence of Helicobacter pylori (HP) infection reported among Malays is also present among aborigines (the Orang Asli) living in northeastern Peninsular Malaysia is unknown. We studied asymptomatic Orang Asli from settlements situated 210 km from the city of Kota Bharu. The HP infection status was confirmed by a validated serology test. Nineteen percent of 480 Orang Asli tested positive for HP infection. The prevalence was 40.6% in the birth cohort of the 1940s and declined steadily in later cohorts to under 10% among 12-30 year olds. This may be related to the phases of relocation from the jungles into resettlement camps and ultimately into designated villages near rivers. The low prevalence pattern after the 1970s was probably partly a result of improvement in sanitation and hygiene practice in these villages but other unidentified factors may also be operating.
  17. Basuni M, Muhi J, Othman N, Verweij JJ, Ahmad M, Miswan N, et al.
    Am. J. Trop. Med. Hyg., 2011 Feb;84(2):338-43.
    PMID: 21292911 DOI: 10.4269/ajtmh.2011.10-0499
    Soil-transmitted helminth infections remain a major public health burden in low- and middle-income countries. The traditional diagnosis by microscopic examination of fecal samples is insensitive and time-consuming. In this study, a pentaplex real-time polymerase chain reaction (PCR) was evaluated for the simultaneous detection of Ancylostoma, Necator americanus, Ascaris lumbricoides, and Strongyloides stercoralis. The results were compared with those obtained by conventional parasitological diagnostic methods. Real-time PCR was positive in 48 of 77 samples (62.3%) and microscopic examination was positive in six samples (7.8%) only (P < 0.05). In conclusion, the real-time PCR assay described in this study provides a specific and sensitive diagnostic tool for the detection of these four helminth species in epidemiological studies and monitoring of treatment programs.
  18. Al-Mekhlafi HM, Surin J, Sallam AA, Abdullah AW, Mahdy MA
    Am. J. Trop. Med. Hyg., 2010 Sep;83(3):523-7.
    PMID: 20810815 DOI: 10.4269/ajtmh.2010.09-0371
    A cross-sectional study was carried out on 241 primary schoolchildren in Pahang, Malaysia to update their vitamin A status and to investigate the association of poor vitamin A status with their health and socioeconomic factors. All children were screened for intestinal parasitic infections. Blood samples were collected and vitamin A status was assessed. Socioeconomic data were collected by using pre-tested questionnaires. The results showed that 66 (27.4%) children had low serum retinol levels (< 0.70 micromol/L). Giardiasis and severe ascariasis were significantly associated with low serum retinol levels (P = 0.004 and P = 0.018, respectively). Logistic regression confirmed the significant association of giardiasis with low serum retinol (odds ratio = 2.7, 95% confidence interval = 1.3-5.5). In conclusion, vitamin A deficiency is still a public health problem in rural Malaysia. Vitamin A supplementation and treatment of intestinal parasitic infections should be distributed periodically to these children to improve their health and nutritional status.
  19. Wang SM, Sekaran SD
    Am. J. Trop. Med. Hyg., 2010 Sep;83(3):690-5.
    PMID: 20810840 DOI: 10.4269/ajtmh.2010.10-0117
    A commercial Dengue Duo rapid test kit was evaluated for early dengue diagnosis by detection of dengue virus NS1 antigen and immunoglobulin M (IgM)/IgG antibodies. A total of 420 patient serum samples were subjected to real-time reverse transcription-polymerase chain reaction (RT-PCR), in-house IgM capture enzyme-linked immunosorbent assay (ELISA), hemagglutination inhibition assay, and the SD Dengue Duo rapid test. Of the 320 dengue acute and convalescent sera, dengue infection was detected by either serology or RT-PCR in 300 samples (93.75%), as compared with 289 samples (90.31%) in the combined SD Duo NS1/IgM. The NS1 detection rate is inversely proportional, whereas the IgM detection rate is directly proportional to the presence of IgG antibodies. The sensitivity and specificity in diagnosing acute dengue infection in the SD Duo NS1/IgM were 88.65% and 98.75%, respectively. The assay is sensitive and highly specific. Detection of both NS1 and IgM by SD Duo gave comparable detection rate by either serology or RT-PCR.
  20. Newton PN, Rolain JM, Rasachak B, Mayxay M, Vathanatham K, Seng P, et al.
    Am. J. Trop. Med. Hyg., 2009 Aug;81(2):190-4.
    PMID: 19635868
    Neorickettsia sennetsu has been described from Japan and Malaysia, causing a largely forgotten infectious mononucleosis-like disease. Because it is believed to be contracted from eating raw fish, frequently consumed in the Lao PDR, we looked for evidence of N. sennetsu among Lao patients and fish. A buffy coat from 1 of 91 patients with undifferentiated fever was positive by 16S rRNA amplification and sequencing and real-time polymerase chain reactions (PCR) targeting two N. sennetsu genes. Lao blood donors and patients with fever, hepatitis, or jaundice (N = 1,132) had a high prevalence (17%) of immunofluorescence assay IgG anti-N. sennetsu antibodies compared with 4% and 0% from febrile patients (N = 848) in Thailand and Malaysia, respectively. We found N. sennetsu DNA by PCR, for the first time, in a fish (Anabas testudineus). These data suggest that sennetsu may be an under-recognized cause of fever and are consistent with the hypothesis that it may be contracted from eating raw fish.
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