Displaying publications 1 - 20 of 119 in total

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  1. Lim YA, Aahmad RA
    PMID: 15916072
    A survey of the river water frequently used by the Temuan Orang Asli (aborigine) indicated that 66.7% of the river water samples were Giardia cyst positive and 5.6% were Cryptosporidium oocyst positive. Although Giardia cysts were detected in samples from all the sites (e.g. upstream, midstream, and downstream), Cryptosporidium was only present in one river water sample taken from downstream from a village. The only sample of upstream water which contained Giardia cysts had a concentration of 0.7 cysts/l. All samples taken from midstream contained cysts with a mean concentration of 9.8 +/- 6.6 cysts/l (range = 1-20 cysts/l). Eighty-three point three percent of the samples collected from downstream contained cysts and 16.7% had oocysts. The average concentration of cysts was 12.9 +/- 16.4 cysts/l (range = 0-44 cysts/l), whereas the oocyst concentration was 0.4 oocysts/l. All river samples tested positive for the presence of E. coli, indicating fecal contamination. The results of this study imply that the river system is contaminated with fecal-oral transmitted parasites. The river water, used by the Orang Asli, is a probable route for Giardia and Cryptosporidium transmission in this community. Long term strategies, incorporating health education regarding personal hygiene, and provision of toilets and the importance of their proper usage, need to be embraced by this community in order to control the spread of these parasites.
  2. Ngui R, Lim YA, Chua KH
    PLoS ONE, 2012;7(7):e41996.
    PMID: 22844538 DOI: 10.1371/journal.pone.0041996
    Hookworm infections are still endemic in low and middle income tropical countries with greater impact on the socioeconomic and public health of the bottom billion of the world's poorest people. In this study, a real-time polymerase chain reaction (PCR) coupled with high resolution melting-curve (HRM) analysis was evaluated for an accurate, rapid and sensitive tool for species identification focusing on the five human hookworm species.
  3. Lim YA, Wan Hafiz WI, Nissapatorn V
    Trop Biomed, 2007 Jun;24(1):95-104.
    PMID: 17568382 MyJurnal
    Cryptosporidium and Giardia are two important pathogenic parasites that have caused many waterborne outbreaks which affected hundreds of thousands of people. Contamination from effluent discharged by sewage treatment plants have been implicated in previous waterborne outbreaks of Cryptosporidium and Giardia. This study evaluated the reduction of Cryptosporidium and Giardia (oo)cysts in two sewage treatment plants (STPA and STPB) in Malaysia which employed different treatment processes for a period of a year. Raw sewage influents and treated sewage effluents were concentrated by repeated centrifugation, subjected to sucrose density flotation and concentrated to a minimal volume depending upon the levels of contaminating debris. Cryptosporidium oocysts and Giardia cysts were enumerated using epifluorescence microscopy. The parasite concentrations in raw sewage were 18-8480 of Giardia cysts/litre and 1-80 of Cryptosporidium oocysts/litre. In treated sewage, the concentration of parasites ranged from 1-1462 cysts/litre and 20-80 oocysts/ litre for Giardia and Cryptosporidium respectively. Statistical analysis showed that sewage treatment process which employed extended aeration could reduce the concentration of Cryptosporidium and Giardia (oo)cysts significantly but treatment process which encompasses aerated lagoon could only reduce the concentration of Giardia cysts but not Cryptosporidium oocysts significantly. This phenomenon is of great concern in areas whereby effluent of sewage treatment plants is discharged into the upstream of rivers that are eventually used for abstraction of drinking water. Therefore, it is important that wastewater treatment authorities rethink the relevance of Cryptosporidium and Giardia contamination levels in wastewater and watersheds and to develop countermeasures in wastewater treatment plants. Further epidemiological studies on the occurrence and removal of pathogenic organisms from excreta and sewage are also recommended, in order that the public health risks can be defined and the most cost effective sewage treatment options developed.
  4. Ahmad AF, Ngui R, Muhammad Aidil R, Lim YA, Rohela M
    Trop Biomed, 2014 Dec;31(4):836-43.
    PMID: 25776610 MyJurnal
    Limited data is available on the prevalence of parasitic infections among the island communities in Malaysia with most studies performed between 1960s-1980s. This study was conducted to determine the current prevalence status of parasitic infections among communities living in Pangkor Island Peninsular Malaysia. A total of 131 stool and 298 serum samples were collected and subjected to microscopic examination for intestinal protozoa and helminths and detection of Toxoplasma gondii antibodies using commercial ELISA kits respectively. In addition, thin and thick peripheral blood films were microscopically screened for the presence of Plasmodium spp. and microfilariae respectively. The overall prevalence of intestinal parasitic infections among Pangkor Island community was 9.9% (13/131) with T. trichiura (5.3%) being the most common intestinal parasite detected. Toxoplasmosis was reported in almost 60% of the community with the seroprevalence being significantly high among females (64.7%) compared to males (52.8%) (p=0.038). None of those examined samples were infected with intestinal sarcocystosis, malaria and filariasis. This study revealed that the prevalence of intestinal parasitic infections among Pangkor Island community has been greatly reduced compared to that reported 35 years ago. Massive improvements in the socioeconomic status, personal hygiene, water facilities and sanitation may have contributed to the low prevalence of parasitic infections in this community. Nevertheless, further studies still need to be performed to determine the possible risk factors for the high prevalence of toxoplasmosis in this community.
  5. Bamaga OA, Mahdy MA, Mahmud R, Lim YA
    Parasit Vectors, 2014;7:351.
    PMID: 25074325 DOI: 10.1186/1756-3305-7-351
    Yemen is a Mediterranean country where 65% of its population is at risk of malaria, with 43% at high risk. Yemen is still in the control phase without sustainable reduction in the proportion of malaria cases. A cross-sectional household survey was carried out in different districts in the southeast of the country to determine malaria prevalence and identify factors that impede progress of the elimination phase.
  6. Tay ST, Mohamed Zan HA, Lim YA, Ngui R
    PLoS Negl Trop Dis, 2013;7(8):e2341.
    PMID: 23936576 DOI: 10.1371/journal.pntd.0002341
    Limited data is available on the current status of scrub typhus infection in the aboriginal population in Malaysia. This study was aimed to provide recent data on the degree of exposure of 280 individuals from seven aboriginal subgroups to Orientia tsutsugamushi (causative agent of scrub typhus) in West Malaysia. The environment, socioeconomic and behavioural risk factors associated with the disease were also investigated.
  7. Ahmad AF, Hadip F, Ngui R, Lim YA, Mahmud R
    Parasitol. Res., 2013 Aug;112(8):2811-6.
    PMID: 23666229 DOI: 10.1007/s00436-013-3450-z
    Detection of Strongyloides stercoralis infection particularly in asymptomatic individuals is often hampered due to the lack of standard diagnostic tools. In this study, the use of serological and molecular approaches were investigated for the detection of S. stercoralis infection among an Orang Asli (indigenous) community following a preliminary detection by microscopic examination of faecal samples. Out of 54 individuals studied, 17/54 (31.5%) were detected to be positive for S. stercoralis infection by enzyme-linked immunosorbent assay (ELISA), compared to 0/54 (0%) by faecal examination. Further confirmation performed by a nested polymerase chain reaction (PCR) using DNA extracted from faecal samples of these 17 individuals yielded 3/17 (17.6%) positives for S. stercoralis DNA amplification. No amplification was seen with the other 37 faecal samples, which were negative by microscopy and ELISA. As the high ELISA positive results were suspected to be false-positives, ELISA is not recommended for use as a detection tool but may be beneficial for evaluating the effectiveness of anti-Strongyloides drugs. The present finding indicated that PCR should be considered as an alternative diagnostic tool for the detection of S. stercoralis infection.
  8. Alyousefi NA, Mahdy MA, Lim YA, Xiao L, Mahmud R
    Parasitology, 2013 May;140(6):729-34.
    PMID: 23369243 DOI: 10.1017/S0031182012001953
    Cryptosporidium is a protozoan parasite of humans and animals and has a worldwide distribution. The parasite has a unique epidemiology in Middle Eastern countries where the IId subtype family of Cryptosporidium parvum dominates. However, there has been no information on Cryptosporidium species in Yemen. Thus, this study was conducted in Yemen to examine the distribution of Cryptosporidium species and subtype families. Fecal samples were collected from 335 patients who attended hospitals in Sana'a city. Cryptosporidium species were determined by PCR and sequence analysis of the 18 s rRNA gene. Cryptosporidium parvum and C. hominis subtypes were identified based on sequence analysis of the 60 kDa glycoprotein (gp60) gene. Out of 335 samples, 33 (9.9%) were positive for Cryptosporidium. Of them, 97% were identified as C. parvum whilst 1 case (3%) was caused by C. hominis. All 7 C. parvum isolates subtyped belonged to the IIaA15G2R1 subtype. The common occurrence of the zoonotic IIa subtype family of C. parvum highlights the potential occurrence of zoonotic transmission of cryptosporidiosis in Yemen. However, this postulation needs confirmation with future molecular epidemiological studies of cryptosporidiosis in both humans and animals in Yemen.
  9. Bamaga OA, Mahdy MA, Lim YA
    Malar. J., 2015;14:516.
    PMID: 26693691 DOI: 10.1186/s12936-015-1035-2
    Malaria in Yemen is mainly caused by Plasmodium falciparum and 25% of the population is at high risk. Sulfadoxine-pyrimethamine (SP) had been used as monotherapy against P. falciparum. Emergence of chloroquine resistance led to the shift in anti-malarial treatment policy in Yemen to artemisinin-based combination therapy, that is artesunate (AS) plus SP as first-line therapy for uncomplicated malaria and artemether-lumefantrine as second-line treatment. This study aimed to screen mutations in the dihydrofolate reductase (dhfr) and dihydropteroate synthetase (dhps) genes associated with SP resistance among P. falciparum population in Hadhramout governorate, Yemen.
  10. Bamaga OA, Mahdy MA, Lim YA
    Acta Trop., 2015 Sep;149:59-63.
    PMID: 26001972 DOI: 10.1016/j.actatropica.2015.05.013
    Malaria is still a major public health problem in Yemen. More than 95% of the malaria cases are due to Plasmodium ‎falciparum‎. Recently in Yemen, the antimalarial treatment policy was changed from chloroquine (CQ) to artemisinin combination therapy (ACTs). However, CQ is still available and prescribed in the Yemeni market. The persistence of CQ resistance will be prolonged if the shift to ACT and the simultaneous withdrawal of CQ are not rigorously implemented. The aim of the current survey is to detect chloroquine-resistant mutations in P. falciparum chloroquine-resistance transporter (pfcrt) and P. falciparum multi-drug resistance-1 (pfmdr1) genes. These data will be important for future monitoring and assessment of antimalarial drug policy in Yemen. Blood specimens were collected from 735 individuals from different districts of the Hadhramout province, Yemen by house-to-house visit. Mutation-specific nested polymerase chain reaction (PCR) and restriction fragment length polymorphism (PCR-RFLP) methods were used to investigate the mutations in the pfmdr1(codons 86 and 1246) and pfcrt (codons 76, 271, 326, 356 and 371) genes. The overall prevalence of pfcrt mutations at codons 76, 271, 326 and 371 were 50.4%, 58.7%, 54.3% and 44.9%, respectively. All isolates had wild-type pfcrt 356 allele. The majority of pfmdr1 86 alleles (83.3%) and all pfmdr1 1246 alleles were wild type. There was no association between pfcrt mutations and symptomatology, gender and age groups. In conclusion, point mutations in codons 76, 271, 326 and 371 of pfcrt of P. falciparum are high suggesting a sustained high CQ resistance even after 4 years of shifting to ACTs. These findings warrant complete withdrawal of CQ use from the Yemeni market for P. falciparum and careful usage of CQ for treating Plasmodium vivax.
  11. Ngui R, Lim YA, Traub R, Mahmud R, Mistam MS
    PLoS Negl Trop Dis, 2012;6(2):e1522.
    PMID: 22347515 DOI: 10.1371/journal.pntd.0001522
    Currently, information on species-specific hookworm infection is unavailable in Malaysia and is restricted worldwide due to limited application of molecular diagnostic tools. Given the importance of accurate identification of hookworms, this study was conducted as part of an ongoing molecular epidemiological investigation aimed at providing the first documented data on species-specific hookworm infection, associated risk factors and the role of domestic animals as reservoirs for hookworm infections in endemic communities of Malaysia.
  12. Iqbal A, Lim YA, Surin J, Sim BL
    PLoS ONE, 2012;7(2):e31139.
    PMID: 22347442 DOI: 10.1371/journal.pone.0031139
    Currently, there is a lack of vital information in the genetic makeup of Cryptosporidium especially in developing countries. The present study aimed at determining the genotypes and subgenotypes of Cryptosporidium in hospitalized Malaysian human immunodeficiency virus (HIV) positive patients.
  13. Asma I, Johari S, Sim BL, Lim YA
    Trop Biomed, 2011 Aug;28(2):400-10.
    PMID: 22041762 MyJurnal
    Human immunodeficiency virus (HIV)-infected individuals have greater susceptibility to infections by a myriad of microorganisms which can cause significant morbidity and mortality compared to immunocompetent individuals. Of these microbial infections, intestinal parasitic infections (IPIs) however are receiving less attention than bacterial and viral infections, hence, the lack of information of parasitic infections in HIV individuals. Prevalence of IPIs among 346 HIV-infected individuals in Malaysia was determined in this study. The overall prevalence of intestinal parasitic infections (IPIs) was 37.9% (131 of 346) with protozoa infections (18.8%) being more common compared to helminth infections (7.5%). Observed protozoa include Entamoeba histolytica/dispar (16.8%), Cryptosporidium parvum (12.4%), Isospora belli (10.1%), Cyclospora cayetanensis (4.9%) and Giardia duodenalis (intestinalis) (3.2%) whilst helminthes which were detected comprised of Ascaris lumbricoides (13.9%), Trichuris trichiura (6.4%) and hookworms (0.6%). Among those 131 infected, 50.4% had multiple infections and 48.9% had single parasitic infection. The CD4 counts were significantly lower (i.e., 200 cells/mm³) in patients harbouring IPIs. Of those individuals infected with intestinal parasites, 49% were intravenous drug users and 58% were not on any antiretroviral therapy. Most were asymptomatic and had concurrent opportunistic infections (OIs) mainly with Mycobacterium tuberculosis infection. These results confirmed that IPIs are ubiquitous among HIV-infected individuals, especially those presenting with low CD4 T cells counts, and provide useful insights into the epidemiology of these infections among HIV-infected patients in Malaysia. It is therefore recommended, that diagnosis of these intestinal parasitic pathogens should be conducted on a routine basis for better management of gastrointestinal illnesses among HIV individuals.
  14. Sejdini A, Mahmud R, Lim YA, Mahdy M, Sejdini F, Gjoni V, et al.
    Ann Trop Med Parasitol, 2011 Apr;105(3):241-50.
    PMID: 21801503 DOI: 10.1179/136485911X12987676649584
    Although intestinal parasitic infections (IPI) among children remain a global issue, the current information on such infections in Albanian children is very limited. A cross-sectional study of the IPI in 321 children living in the Albanian counties of Tirana (152) and Elbasan (169) was therefore conducted in 2008, with a pre-tested standard questionnaire employed to gather the relevant personal and clinical data. Using formalin-ether concentration and permanent stains, stool samples were examined microscopically for the ova, cysts and oocysts of any parasites. The overall prevalence of IPI was 19% (61 of 321), with protozoan infections (11·5%) apparently more common than infections with soil-transmitted helminths (STH; 8·1%). Giardia duodenalis was the parasite most frequently detected (10·9%), followed by hookworm (5·6%), Ascaris lumbricoides (1·9%), Trichuris trichiura (0·6%), Cryptosporidium (0·3%) and Entamoeba histolytica/dispar (0·3%). The results of a univariate analysis indicated that the children from Tirana county were significantly more likely to be found infected with STH compared with the children from Elbasan county (12·5% v. 4·1%; P=0·006). Children sampled in the community were also more likely to be found STH-positive than the children sampled as they attended hospitals and health clinics (10·5% v. 6·0%) but this difference did not reach statistical significance. The children found STH-positive were five times more likely to be suffering from diarrhoea than the other children checked in clinical settings (P=0·004) and were also more likely to be suffering from abdominal pain (P=0·054) and/or diminished appetite (P=0·016).
  15. Ngui R, Ishak S, Chuen CS, Mahmud R, Lim YA
    PLoS Negl Trop Dis, 2011;5(3):e974.
    PMID: 21390157 DOI: 10.1371/journal.pntd.0000974
    Intestinal parasitic infections (IPIs) have a worldwide distribution and have been identified as one of the most significant causes of illnesses and diseases among the disadvantaged population. In Malaysia, IPIs still persist in some rural areas, and this study was conducted to determine the current epidemiological status and to identify risk factors associated with IPIs among communities residing in rural and remote areas of West Malaysia.
  16. Alyousefi NA, Mahdy MA, Mahmud R, Lim YA
    PLoS ONE, 2011;6(7):e22044.
    PMID: 21789210 DOI: 10.1371/journal.pone.0022044
    Intestinal protozoan diseases in Yemen are a significant health problem with prevalence ranging from 18% to 27%. The present study is a cross-sectional study aimed at determining the factors associated with the high prevalence of intestinal protozoan infections among patients seeking health care in Sana'a City, the capital of Yemen.
  17. Lim YA, Romano N, Colin N, Chow SC, Smith HV
    Trop Biomed, 2009 Aug;26(2):110-22.
    PMID: 19901897 MyJurnal
    Orang Asli are the indigenous minority peoples of peninsular Malaysia. Despite proactive socioeconomic development initiated by the Malaysian Government in upgrading the quality of life of the Orang Asli communities since 1978, they still remained poor with a current poverty rate of 76.9%. Poverty exacerbates the health problems faced by these communities which include malnourishment, high incidences of infectious diseases (eg. tuberculosis, leprosy, malaria) and the perpetual problem with intestinal parasitic infections. Studies reported that the mean infection rate of intestinal parasitic infections in Orang Asli communities has reduced from 91.1% in 1978, to 64.1% in the subsequent years. Although the results was encouraging, it has to be interpreted with caution because nearly 80% of studies carried out after 1978 still reported high prevalence (i.e. >50%) of soil-transmitted helminthiases (STH) among Orang Asli communities. Prior to 1978, hookworm infection is the most predominant STH but today, trichuriasis is the most common STH infections. The risk factors for intestinal parasitic infections remained unchanged and studies conducted in recent years suggested that severe STH infections contributed to malnutrition, iron deficiency anaemia and low serum retinol in Orang Asli communities. In addition, STH may also contribute to poor cognitive functions and learning ability. Improvements in socioeconomic status in Malaysia have shown positive impact on the reduction of intestinal parasitic infections in other communities however, this positive impact is less significant in the Orang Asli communities. In view of this, a national parasitic infections baseline data on morbidity and mortality in the 18 subgroups of Orang Asli, will assist in identifying intervention programmes required by these communities. It is hope that the adoption of strategies highlighted in the World Health Organisation- Healthy Village Initiatives (WHO-HVI) into Orang Asli communities will ensure the whole mechanism of delivery and empowerment by the government agencies become more efficient and productive in alleviating intestinal parasitic infections in these communities.
  18. Lim YA, Ahmad RA, Smith HV
    J Water Health, 2008 Jun;6(2):239-54.
    PMID: 18209286 DOI: 10.2166/wh.2008.023
    Cryptosporidium and Giardia are major causes of diarrhoeal diseases of humans worldwide, and are included in the World Health Organisation's 'Neglected Diseases Initiative'. Cryptosporidium and Giardia occur commonly in Malaysian human and non-human populations, but their impact on disease, morbidity and cost of illness is not known. The commonness of contributions from human (STW effluents, indiscriminate defaecation) and non-human (calving, lambing, muck spreading, slurry spraying, pasturing/grazing of domestic animals, infected wild animals) hosts indicate that many Malaysian environments, particularly water and soil, are sufficiently contaminated to act as potential vehicles for the transmission of disease. To gain insight into the morbidity and mortality caused by human cryptosporidiosis and giardiasis, they should be included into differential diagnoses, and routine laboratory testing should be performed and (as for many infectious diseases) reported to a centralised public health agency. To understand transmission routes and the significance of environmental contamination better will require further multidisciplinary approaches and shared resources, including raising national perceptions of the parasitological quality of drinking water. Here, the detection of Cryptosporidium and Giardia should be an integral part of the water quality requirement. A multidisciplinary approach among public health professionals in the water industry and other relevant health- and environment-associated agencies is also required in order to determine the significance of Cryptosporidium and Giardia contamination of Malaysian drinking water. Lastly, adoption of validated methods to determine the species, genotype and subgenotype of Cryptosporidium and Giardia present in Malaysia will assist in developing effective risk assessment, management and communication models.
  19. Lim YA, Ngui R, Shukri J, Rohela M, Mat Naim HR
    Vet. Parasitol., 2008 Oct 20;157(1-2):154-9.
    PMID: 18723289 DOI: 10.1016/j.vetpar.2008.07.015
    A survey was undertaken to investigate the prevalence of intestinal parasites from different groups of mammals housed in a zoological garden in Malaysia. A total of 197 faecal samples were collected randomly from various primates (99), hoofed mammals (70) and feline (28). It was discovered that 89.3% of feline, 54.5% of primates and 45.7% of hoofed mammals were infected with intestinal parasites. Intestinal parasites found in primates were Balantidium coli (19.2%), Cryptosporidium spp. (14.1%), hookworm (10.1%), Trichuris spp. (5.1%), Ascaris (4.0%) and Blastocystis spp. (2.0%). For hoofed mammals, hookworm had the highest prevalence (34.3%) followed by Trichuris spp. and Cryptosporidium spp. (5.7%). Meanwhile, for feline, Toxocara cati was the most prevalent (64.3%), followed by Cryptosporidium spp. (14.3%), Spirometra spp. (7.1%), and hookworm (3.6%). Animals that were infected were all asymptomatic with low parasite load. Routine monitoring of the presence of parasites in animals kept in the zoo is imperative in assisting zoo management in the formulation and implementation of preventive and control measures against the spread of infectious parasitic diseases among animals within the zoo or to humans.
  20. Lim YA, Rohela M, Sim BL, Jamaiah I, Nurbayah M
    PMID: 16438176
    A total of 66 fecal specimens obtained from patients infected with human immunodeficiency virus (HIV) from Kajang Hospital were screened for Cryptosporidium oocysts. The fecal specimens were concentrated using the formalin ethyl acetate concentration technique, stained with modified Ziehl-Neelsen and confirmed with immunofluorescence stain. It was established that 2 (3.0%) were positive for Cryptosporidium. The two cases involved a Chinese local man (with diarrhea) and an Indonesian foreigner (without diarrhea). A higher index of suspicion for clinical cryptosporidiosis in HIV patients, including those with chronic weight loss with or without diarrhea, is recommended. In addition, laboratory testing for Cryptosporidium in HIV-infected patients is highly recommended in order to have a better understanding of the epidemiology and management of the disease in Malaysia.
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