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Fulltext Seroprevalence and sources of toxoplasmosis among Orang Asli (indigenous) communities in Peninsular Malaysia

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.
Fulltext Prevalence of bronchial asthma among orang asli in peninsular Malaysia

Ngui R, Lim YA, Chow SC, de Bruyne JA, Liam CK

Med J Malaysia, 2011 Mar;66(1):27-31.
PMID: 23765139 MyJurnal

A survey was carried out to determine the prevalence of bronchial asthma and their contributing risk factors among Orang Asli subgroups living in Malaysia using IUATLD questionnaire and spirometry without being discriminatory towards age or gender. Of the 1171 distributed questionnaires, 716 (61.1%) comprising of 62.7% Semai Pahang, 51.3% Temiar, 74.2% Mah Meri, 65.6% Semai Perak, 53.6% Temuan, 53.8% Semelai, 61.1% Jakun and 67.4% Orang Kuala subgroups completed their questionnaire and were included in the data analysis. Participants comprised 549 (76.7%) children and 167 (23.3%) adults, age between 1 to 83 years old, 304 (42.5%) males and 412 (57.5%) females. The overall prevalence of bronchial asthma was 1.4% of which 1.5% was children, 1.3% adults, 1.0% male and 1.7% female, respectively. Of the 8 subgroups surveyed, 5 out of 10 confirmed asthma cases were Semai Pahang, followed by 3 cases among Mah Meri, and one case each among Temuan and Semai Perak subgroups, respectively. This study also demonstrated that the prevalence of self-reported and confirmed bronchial asthma tend to be higher among those who had close contact with pets, smoking individuals and among those who had a family history of asthma.
Fulltext Fatal case of amoebic liver abscess in a child

Ng KF, Tan KK, Ngui R, Lim YA, Amir A, Rajoo Y, et al.

Asian Pac J Trop Med, 2015 Oct;8(10):878-80.
PMID: 26522307 DOI: 10.1016/j.apjtm.2015.09.018

We reported a case of amoebic liver abscess (ALA) in a 6-year-old Malaysian boy who presented with fever, lethargy, diarrhoea and right hypochondriac pain. On admission he was diagnosed with perforated acute appendicitis and a laparotomy was done. After surgery he developed acute respiratory distress. Ultrasonography, chest X-Ray and CT scan revealed two ALAs in the posterior segment of right lobe of liver, pleural effusion and collapsed consolidation of lungs bilaterally. Percutaneous liver abscesses drainage was done and intravenous Metronidazole was started. PCR carried out on the pus from the abscess was positive for Entamoeba histolytica. Patient however succumbed to the infection one week after admission.
Fulltext Prevalence of filarial parasites in domestic and stray cats in Selangor State, Malaysia

Al-Abd NM, Nor ZM, Kassim M, Mansor M, Al-Adhroey AH, Ngui R, et al.

Asian Pac J Trop Med, 2015 Sep;8(9):705-9.
PMID: 26433654 DOI: 10.1016/j.apjtm.2015.07.034

OBJECTIVE: To determine the prevalence of the filarial parasites,ie.,Brugia malayi, Brugia, Brugia pahangi(B. pahangi), Dirofilaria immitisandDirofilaria repens (D. repens) in domestic and stray cats.
METHODS: A total of 170 blood sample were collected from domestic and stray cats and examined for filarial worm parasites in two localities, Pulau Carey and Bukit Gasing, Selangor State, Malaysia.
RESULTS: The overall prevalence of infection was 23.5% (40/170; 95% CI = 17.4-30.6). Of this, 35% (14/40; 95% CI = 22.1-50.5) and 50% (20/40; 95% CI = 35.2-64.8) were positive for single B. pahangi nd D. repens, respectively. The remaining of 15% (6/40; 95% CI = 7.1-29.1) were positive for mixed B. pahangi and D. repens. In addition, 75% of the infected cats were domestic, and 25% were strays. No Brugia malayi and Dirofilaria immitis was detected. Eighty-four cats were captured at Pulau Carey, of which 35.7% (30/84) were infected. Among the cats determined to be infected, 93% (28/30; 95% CI = 78.7-98.2) were domestic, and only 6.7% (2/30; 95% CI = 19.0-21.3) were strays. Conversely, the number of infected cats was three times lower in Bukit Gasing than in Pulau Carey, and most of the cats were stray.
CONCLUSIONS: B. pahangi and D. repens could be the major parasites underlying filariasis in the study area. Adequate prophylactic plans should be administrated in the cat population in study area.
Molecular characterization of Trichuris species isolated from humans, dogs and cats in a rural community in Peninsular Malaysia

Mohd-Shaharuddin N, Lim YAL, Hassan NA, Nathan S, Ngui R

Acta Trop, 2019 Feb;190:269-272.
PMID: 30500371 DOI: 10.1016/j.actatropica.2018.11.026

Trichuris trichiura (whipworm) are soil-transmitted helminths (STHs) that causing trichuriasis in human. Trichuris vulpis, a canine whipworm has also been reported occasionally in humans. However, an overlapping dimension in the morphology and due to limited external characters between both species may lead to the potential for misidentification. Although there has been an extensive study on the distribution of whipworm in both human and animal hosts, little is known about the molecular epidemiology of Trichuris species in both hosts. To investigate to characterize the whipworm species and to determine the genetic relationship between species infecting both humans and animals, we sequenced the small subunit ribosomal RNA (SSU rRNA) regions of Trichuris egg isolated from humans, dogs and cats in a rural community in Malaysia. A total of 524 fresh fecal samples were collected from humans and animals. The overall prevalence of Trichuris was 59.9% as determined by microscopy examination. The molecular analysis showed that 98.7% were identified as T. trichiura in the human fecal sample. Interestingly, 1.3% were identified as T. vulpis. As for animal fecal sample, 56.8% and 43.2% were identified as T. trichiura and T. vulpis, respectively. Phylogenetic and sequence analysis demonstrated that T. trichiura isolates were genetically distinct from T. vulpis isolates from both hosts. This finding implies that companion animals can be a reservoir and mechanical transmitter for T. trichiura infection in human and also highlighting the possible zoonotic potential of T. vulpis. This finding may also suggest that cross-transmission between humans and animal hosts in sympatric setting may be a source of infection in both hosts. More studies are needed to better understand the transmission dynamic and public health significance of Trichuris infection in both hosts.
Vertical infestation of the dengue vectors Aedes aegypti and Aedes albopictus in apartments in Kuala Lumpur, Malaysia

Roslan MA, Shafie A, Ngui R, Lim YA, Sulaiman WY

J Am Mosq Control Assoc, 2013 Dec;29(4):328-36.
PMID: 24551965

Dengue is a serious public health problem in Malaysia. The aim of this study was to compare the vertical infestation of Aedes population in 2 apartments in Kuala Lumpur with different status of dengue incidence (i.e., high-dengue-incidence area and area with no reported dengue cases). The study was also conducted to assess the relationship between environmental factors such as rainfall, temperature, and humidity and Aedes population that may influence Aedes infestation. Surveillance with a mosquito larvae trapping device was conducted for 28 continuous weeks (January to July 2012) in Vista Angkasa (VA) and Inderaloka (IL) apartments located in Kuala Lumpur, Malaysia. The results indicated that both Aedes spp. could be found from ground to higher floor levels of the apartments, with Aedes aegypti being more predominant than Ae. albopictus. Data based on mixed and single breeding of Aedes spp. on different floors did not show any significant difference. Both rainfall (R3; i.e., the amount of rainfall collected during the previous 3 wk before the surveillance period began) and RH data showed significant relationship with the number of Aedes larvae collected in VA and IL. No significant difference was found between the numbers of Aedes larvae in both study areas as well as maximum and minimum temperatures. Results also indicated adaptations of Ae. aegypti to the ecosystem at each elevation of high-rise buildings, with Ae. albopictus staying inside of apartment units.
Mosquito Biology and Mosquito-Borne Disease Awareness Among Island Communities In Malaysia

Shafie A, Roslan MA, Ngui R, Lim YA, Sulaiman WY

J Am Mosq Control Assoc, 2016 Dec;32(4):273-281.
PMID: 28206867 DOI: 10.2987/16-6604.1

Mosquito-borne diseases have been increasing at an alarming rate over the past decades. In Malaysia, one finds several important mosquito-borne diseases such as Japanese encephalitis, dengue, malaria, and chikungunya. Mosquito surveillance and control programs are the most effective way of detecting and controlling mosquito-borne diseases, but these programs are less effective without an aware and well-informed general public. In 2014 we used a questionnaire to evaluate the extent of awareness of basic mosquito biology and mosquito-borne diseases in 6 villages, Kampung Masjid, Kampung Teluk Gedung, Kampung Teluk Dalam, Kampung Ujung Kelawai, Kampung Sungai Pinang Besar, and Kampung Sungai Pinang Kechil on Pangkor Island, Malaysia. A total of 1,012 individuals responded to the questionnaire, consisting of 790 Malay (78.1%), 164 Chinese (16.2%), and 58 Indian (5.7%). More than 60% (Malay = 73.7%, Chinese = 64.0%, Indian = 79.3%) of the respondents were familiar with basic mosquito biology and practiced personal protection against mosquito bites, and the association was statistically significant (P = 0.02). However, the majority of the respondents had limited knowledge on mosquito-borne diseases, and this varied significantly among the 3 ethnic groups (P = 0.0001). Our recommendations are to improve and intensify public health education outreach programs to the island residents and to encourage community participation in vector control programs.
High Seroprevalence Against Typhus Group and Spotted Fever Group Rickettsiae in Rural Indigenous Populations of Peninsular Malaysia

Tappe D, Gross Y, Ngui R, Rauch J, Tay ST, Lim YAL

Vector Borne Zoonotic Dis, 2019 05;19(5):323-327.
PMID: 30540546 DOI: 10.1089/vbz.2018.2391

Rickettsioses of the typhus group (TG) and spotted fever group (SFG) are emerging bacterial infections worldwide, especially in the tropics. Only a few studies on these pathogens and their respective clinical diseases have been conducted in Malaysia. Here, we performed a seroprevalence study among 544 healthy, afebrile indigenous people (Orang Asli) from peninsular Malaysia for TG and SFG rickettsioses in nine rural and peri-urban settlements. The study population encompassed children, adolescents, and adults. The overall seroprevalence of rickettsiosis in the Orang Asli was 48.5%, with 27.9% seroprevalence against TG rickettsiae and 20.6% seroprevalence against SFG rickettsiae. In 7.9% of the study participants, antibodies against both rickettsial groups were found. The highest seropositivity rates against TG and SRG rickettsiae were detected in young children and adults. Overall, there were no gender differences. Seroprevalences were similar among inhabitants of different settlements, except for two localities. More studies are needed to shed more light on the ecology and risk factors for TG and SFG rickettsioses in Malaysia.
Fulltext Distribution of mosquito larvae in various breeding sites in National Zoo Malaysia

Muhammad-Aidil R, Imelda A, Jeffery J, Ngui R, Wan Yusoff WS, Aziz S, et al.

Trop Biomed, 2015 Mar;32(1):183-6.
PMID: 25801269 MyJurnal

Mosquitoes are principal vectors of major vector-borne diseases. They are widely found throughout urban and rural areas in Malaysia. They are responsible for various vector-borne diseases such as dengue, malaria, filariasis and encephalitis. A total of 158 mosquito larvae specimens were collected from the National Zoo, Malaysia, from 11 types of breeding habitats during the study period from end of May 2007 to July 2007. Aedes albopictus was the predominant species (35.4%), followed by Tripteroides aranoides (26.6%), Lutzia halifaxii (11.4%), Aedes alboscutellatus (10.1%), Aedes caecus (8.9%), Armigeres spp. (4.4%), Malaya genurostris (2.5%) and Culex vishnui (0.6%). It is important to have a mosquito free environment in a public place like the zoo. Routine larval surveillance should be implemented for an effective mosquito control program in order to reduce mosquito population.
Fulltext A case report of Hymenolepis diminuta infection in a Malaysian child

Rohela M, Ngui R, Lim YA, Kalaichelvan B, Wan Hafiz WI, Mohd Redzuan AN

Trop Biomed, 2012 Jun;29(2):224-30.
PMID: 22735844 MyJurnal

We report a case of Hymenolepis diminuta infection in a 2-year-old Malaysian child. This case was initially reported as 'normal' after the examination of proglottids shed from the anus of the child at a private laboratory on two occasions. The putative proglottids shed was then referred to the Parasite Southeast Asia Diagnostic (Para:SEAD) Laboratory, Department of Parasitology, Faculty of Medicine, University of Malaya for further examination. Microscopic examination confirmed that the child was infected with H. diminuta based on the characteristic eggs found in the proglottids. She was treated with a single dose praziquantel (20 mg/kg of body weight) and recovered well.
Fulltext Spatial pattern of 2009 dengue distribution in Kuala Lumpur using GIS application

Aziz S, Ngui R, Lim YA, Sholehah I, Nur Farhana J, Azizan AS, et al.

Trop Biomed, 2012 Mar;29(1):113-20.
PMID: 22543611 MyJurnal

In the last few years in Malaysia, dengue fever has increased dramatically and has caused huge public health concerns. The present study aimed to establish a spatial distribution of dengue cases in the city of Kuala Lumpur using a combination of Geographic Information System (GIS) and spatial statistical tools. Collation of data from 1,618 dengue cases in 2009 was obtained from Kuala Lumpur City Hall (DBKL). These data were processed and then converted into GIS format. Information on the average monthly rainfall was also used to correlate with the distribution pattern of dengue cases. To asses the spatial distribution of dengue cases, Average Nearest Neighbor (ANN) Analysis was applied together with spatial analysis with the ESRI ArcGIS V9.3 programme. Results indicated that the distribution of dengue cases in Kuala Lumpur for the year 2009 was spatially clustered with R value less than 1 (R = 0.42; z-scores = - 4.47; p < 0.001). Nevertheless, when this pattern was further analyzed according to month by each zone within Kuala Lumpur, two distinct patterns were observed which include a clustered pattern (R value < 1) between April to June and a dispersed pattern (R value > 1) between August and November. In addition, the mean monthly rainfall has not influenced the distribution pattern of the dengue cases. Implementation of control measures is more difficult for dispersed pattern compared to clustered pattern. From this study, it was found that distribution pattern of dengue cases in Kuala Lumpur in 2009 was spatially distributed (dispersed or clustered) rather than cases occurring randomly. It was proven that by using GIS and spatial statistic tools, we can determine the spatial distribution between dengue and population. Utilization of GIS tools is vital in assisting health agencies, epidemiologist, public health officer, town planner and relevant authorities in developing efficient control measures and contingency programmes to effectively combat dengue fever.
Over two decades of Plasmodium knowlesi infections in Sarawak: Trend and forecast

Ooi CH, Bujang MA, Tg Abu Bakar Sidik TMI, Ngui R, Lim YA

Acta Trop, 2017 Dec;176:83-90.
PMID: 28768148 DOI: 10.1016/j.actatropica.2017.07.027

Malaria is still of great public health concern, especially in Malaysian Borneo. The aim of this study was to determine the trends of P. knowlesi infection in Sarawak, Malaysia and to forecast the incidence of P. knowlesi until the year 2040. Data on P. knowlesi malaria cases from 1992 to the year 2014 were obtained from the Sarawak Health Department, Malaysia. ARIMA model was applied to forecast the future incidence of P. knowlesi infection. The data for the whole of Sarawak and subsequently the selected six districts which have high incidence rates of P. knowlesi infection were analyzed. Results of the analysis showed that there was an increasing trend of P. knowlesi cases from the year 1992-2014 (p<0.001). The trend in the incidence started to increase in the year 2008 (p=0.029). The incidence rate per 100,000 populations was between 4.15 in the year 1992 and 42.03 in the year 2014. High incidence of P. knowlesi infections has been detected in the districts adjacent to each other within the interior region of Sarawak. The forecasted incidence and incidence rate per 100,000 populations in the year 2020 were 1229 and 44.04, respectively, while those in the year 2040 were 2056 and 62.91, respectively. The forecasted incidence showed an upward trend highlighting an urgent need to draw up strategic and holistic prevention plans to limit further the increase in P. knowlesi morbidity and mortality in Sarawak. It is imperative that these measures are customized taking into consideration the challenges faced in the interior areas of Sarawak and the behavior of the main vector of P. knowlesi (i.e., An. latens) in Sarawak.
Fulltext Neglected Intestinal Parasites, Malnutrition and Associated Key Factors: A Population Based Cross-Sectional Study among Indigenous Communities in Sarawak, Malaysia

Rajoo Y, Ambu S, Lim YA, Rajoo K, Tey SC, Lu CW, et al.

PLoS One, 2017;12(1):e0170174.
PMID: 28095446 DOI: 10.1371/journal.pone.0170174

Intestinal parasitic infections (IPIs) have been recognized as one of the most significant causes of illness among disadvantaged communities. Many studies have been conducted on the prevalence of IPIs in Malaysia. However, these studies mostly focused on the indigenous groups in Peninsular Malaysia. The present study was conducted to provide the current baseline data on prevalence of IPIs, anaemia, malnutrition and associated risk factors among the indigenous communities in Sarawak, situation at northwest Borneo island of Malaysia. A cross sectional study was conducted among the longhouses communities. Stool samples were obtained and examined for the presence of IPIs using microscopy technique. Haemoglobin measurement was done using a portable haemoglobin analyzer. Malnutrition (i.e., stunting, underweight and wasting) was assessed using the WHO Anthro software. Statistical analysis was carried out using SPSS software. A total of 341participants took part in this study. The overall prevalence of IPIs was 57.5%. Multivariate analysis indicated that the absence of toilets (OR = 1.6; 95% CI = 1.1-2.7; p = 0.002) and close contact with animals (OR = 1.8; 95% CI = 1.3-2.9; p = 0.027) as significant predictors for IPIs. The incidence of anaemia was 36.4%. The incidence of underweight, wasting and stunting were 22.2%, 5.6% and 35.4%, respectively. Multivariate analysis demonstrated that low level of parental education attainment (OR = 1.9; 95% CI = 1.2-3.0; p = 0.006) was identified as significant predictor for anaemia. The incidence of wasting was significantly associated with mild anaemia (OR = 1.2; 95% CI = 0.9-1.7; p = 0.024). Low household income was identified as significant predictor for stunting (OR = 2.1; 95% CI = 9.8-22.2; p = 0.001) and underweight (OR = 1.9; 95% CI = 5.6-18.7; p = 0.037), respectively. Essentially, the present study highlighted that intestinal parasitic infections, anaemia and malnutrition are still prevalent among rural indigenous community in Sarawak. Improvement of socioeconomic status, periodic mass deworming, iron supplementation and health education program should be included in the control and prevention of public health strategies.
Fulltext Possible Factors Influencing the Seroprevalence of Dengue among Residents of the Forest Fringe Areas of Peninsular Malaysia

Abd-Jamil J, Ngui R, Nellis S, Fauzi R, Lim ALY, Chinna K, et al.

J Trop Med, 2020;2020:1019238.
PMID: 32536945 DOI: 10.1155/2020/1019238

Dengue is an endemic mosquito-borne viral disease prevalent in many urban areas of the tropic, especially the Southeast Asia. Its presence among the indigenous population of Peninsular Malaysia (Orang Asli), however, has not been well described. The present study was performed to investigate the seroprevalence of dengue among the Orang Asli (OA) residing at the forest fringe areas of Peninsular Malaysia and determine the factors that could affect the transmission of dengue among the OA. Eight OA communities consisting of 491 individuals were recruited. From the study, at least 17% of the recruited study participants were positive for dengue IgG, indicating past exposure to dengue. Analysis on the demographic and socioeconomic variables suggested that high seroprevalence of dengue was significantly associated with those above 13 years old and a low household income of less than MYR500 (USD150). It was also associated with the vast presence of residential areas and the presence of a lake. Remote sensing analysis showed that higher land surface temperatures and lower land elevations also contributed to higher dengue seroprevalence. The present study suggested that both demographic and geographical factors contributed to the increasing risk of contracting dengue among the OA living at the forest fringe areas of Peninsular Malaysia. The OA, hence, remained vulnerable to dengue.
Seroprevalence of Nipah Virus Infection in Peninsular Malaysia

Yong MY, Lee SC, Ngui R, Lim YA, Phipps ME, Chang LY

J Infect Dis, 2020 05 11;221(Suppl 4):S370-S374.
PMID: 32392323 DOI: 10.1093/infdis/jiaa085

Nipah virus (NiV) outbreak occurred in Malaysia in 1998. The natural host reservoir for NiV is Pteropus bats, which are commonly found throughout Malaysia. Humans become infected when NiV spills over from the reservoir species. In this study, NiV serosurveillance in Peninsular Malaysia, particularly among the indigenous population, was performed. The collected samples were tested for presence of NiV antibodies using a comparative indirect enzyme-linked immunosorbent assay based on the recombinant NiV nucleocapsid (rNiV-N) protein. We found that 10.73% of the participants recruited in this study had antibodies against rNiV-N, suggesting possible exposure to NiV.
Aquatic biomonitoring of Giardia cysts and Cryptosporidium oocysts in peninsular Malaysia

Lee SC, Ngui R, Tan TK, Roslan MA, Ithoi I, Lim YA

Environ Sci Pollut Res Int, 2014 Jan;21(1):445-53.
PMID: 23794081 DOI: 10.1007/s11356-013-1925-1

An aquatic biomonitoring of Giardia cysts and Cryptosporidium oocysts in river water corresponding to five villages situated in three states in peninsular Malaysia was determined. There were 51.3% (20/39) and 23.1% (9/39) samples positive for Giardia and Cryptosporidium (oo)cysts, respectively. Overall mean concentration between villages for Giardia cysts ranged from 0.10 to 25.80 cysts/l whilst Cryptosporidium oocysts ranged from 0.10 to 0.90 oocysts/l. Detailed results of the river samples from five villages indicated that Kuala Pangsun 100% (9/9), Kemensah 77.8% (7/9), Pos Piah 33.3% (3/9) and Paya Lebar 33.3% (1/3) were contaminated with Giardia cysts whilst Cryptosporidium (oo)cysts were only detected in Kemensah (100 %; 9/9) and Kuala Pangsun (66.6%; 6/9). However, the water samples from Bentong were all negative for these waterborne parasites. Samples were collected from lower point, midpoint and upper point. Midpoint refers to the section of the river where the studied communities are highly populated. Meanwhile, the position of the lower point is at least 2 km southward of the midpoint and upper point is at least 2 km northward of the midpoint. The highest mean concentration for (oo)cysts was found at the lower points [3.15 ± 6.09 (oo)cysts/l], followed by midpoints [0.66 ± 1.10 (oo)cysts/l] and upper points [0.66 ± 0.92 (oo)cysts/l]. The mean concentration of Giardia cysts was highest at Kuala Pangsun (i.e. 5.97 ± 7.0 cysts/l), followed by Kemensah (0.83 ± 0.81 cysts/l), Pos Piah (0.20 ± 0.35 cysts/l) and Paya Lebar (0.10 ± 0.19 cysts/l). On the other hand, the mean concentration of Cryptosporidium oocysts was higher at Kemensah (0.31 ± 0.19 cysts/l) compared to Kuala Pangsun (0.03 ± 0.03cysts/l). All the physical and chemical parameters did not show significant correlation with both protozoa. In future, viability status and molecular characterisation of Giardia and Cryptosporidium should be applied to identify species and genotypes/subgenotypes for better understanding of the epidemiology of these waterborne parasites.
Fulltext Molecular Diagnosis of Microsporidia among Immunocompromised Patients in Kuala Lumpur, Malaysia

Hassan NA, Lim YAL, Mahmud R, Mohd-Shaharuddin N, Wan Sulaiman WY, Ngui R

Am J Trop Med Hyg, 2018 Dec;99(6):1562-1566.
PMID: 30382015 DOI: 10.4269/ajtmh.17-0901

Microsporidia are obligate intracellular parasitic fungi causing chronic diarrhea, particularly among immunocompromised patients. The current method used for diagnosis is based on conventional microscopy, which does not differentiate parasites at the species level. The present study was carried out to identify microsporidian species in immunocompromised patients. From March 2016 to March 2017, a total of 289 archived stool samples were examined microscopically for microsporidian spores using Gram-chromotrope Kinyoun (GCK) stain. Positive stool samples by microscopy were subjected to polymerase chain reaction and sequencing for species identification. Based on microscopy examination, the overall prevalence of microsporidian infections was 32.2% (93/289; 95% CI = 27.1-37.8). Of these stool samples, 45 samples were successfully amplified and confirmed as Enterocytozoon bieneusi. No Encephalitozoon intestinalis was detected. Accurate identification of species might help clinicians to decide appropriate management strategies as dissemination risks and treatment response vary for different species, hence improving the management of microsporidian infections.
Fulltext Spatial analyses of Plasmodium knowlesi vectors with reference to control interventions in Malaysia

Pramasivan S, Ngui R, Jeyaprakasam NK, Low VL, Liew JWK, Vythilingam I

Parasit Vectors, 2023 Oct 09;16(1):355.
PMID: 37814287 DOI: 10.1186/s13071-023-05984-x

BACKGROUND: Malaria parasites such as Plasmodium knowlesi, P. inui, and P. cynomolgi are spread from macaques to humans through the Leucosphyrus Group of Anopheles mosquitoes. It is crucial to know the distribution of these vectors to implement effective control measures for malaria elimination. Plasmodium knowlesi is the most predominant zoonotic malaria parasite infecting humans in Malaysia.
METHODS: Vector data from various sources were used to create distribution maps from 1957 to 2021. A predictive statistical model utilizing logistic regression was developed using significant environmental factors. Interpolation maps were created using the inverse distance weighted (IDW) method and overlaid with the corresponding environmental variables.
RESULTS: Based on the IDW analysis, high vector abundances were found in the southwestern part of Sarawak, the northern region of Pahang and the northwestern part of Sabah. However, most parts of Johor, Sabah, Perlis, Penang, Kelantan and Terengganu had low vector abundance. The accuracy test indicated that the model predicted sampling and non-sampling areas with 75.3% overall accuracy. The selected environmental variables were entered into the regression model based on their significant values. In addition to the presence of water bodies, elevation, temperature, forest loss and forest cover were included in the final model since these were significantly correlated. Anopheles mosquitoes were mainly distributed in Peninsular Malaysia (Titiwangsa range, central and northern parts), Sabah (Kudat, West Coast, Interior and Tawau division) and Sarawak (Kapit, Miri, and Limbang). The predicted Anopheles mosquito density was lower in the southern part of Peninsular Malaysia, the Sandakan Division of Sabah and the western region of Sarawak.
CONCLUSION: The study offers insight into the distribution of the Leucosphyrus Group of Anopheles mosquitoes in Malaysia. Additionally, the accompanying predictive vector map correlates well with cases of P. knowlesi malaria. This research is crucial in informing and supporting future efforts by healthcare professionals to develop effective malaria control interventions.
An automated malaria cells detection from thin blood smear images using deep learning

Sukumarran D, Hasikin K, Mohd Khairuddin AS, Ngui R, Wan Sulaiman WY, Vythilingam I, et al.

Trop Biomed, 2023 Jun 01;40(2):208-219.
PMID: 37650409 DOI: 10.47665/tb.40.2.013

Timely and rapid diagnosis is crucial for faster and proper malaria treatment planning. Microscopic examination is the gold standard for malaria diagnosis, where hundreds of millions of blood films are examined annually. However, this method's effectiveness depends on the trained microscopist's skills. With the increasing interest in applying deep learning in malaria diagnosis, this study aims to determine the most suitable deep-learning object detection architecture and their applicability to detect and distinguish red blood cells as either malaria-infected or non-infected cells. The object detectors Yolov4, Faster R-CNN, and SSD 300 are trained with images infected by all five malaria parasites and from four stages of infection with 80/20 train and test data partition. The performance of object detectors is evaluated, and hyperparameters are optimized to select the best-performing model. The best-performing model was also assessed with an independent dataset to verify the models' ability to generalize in different domains. The results show that upon training, the Yolov4 model achieves a precision of 83%, recall of 95%, F1-score of 89%, and mean average precision of 93.87% at a threshold of 0.5. Conclusively, Yolov4 can act as an alternative in detecting the infected cells from whole thin blood smear images. Object detectors can complement a deep learning classification model in detecting infected cells since they eliminate the need to train on single-cell images and have been demonstrated to be more feasible for a different target domain.
Fulltext Association between anaemia, iron deficiency anaemia, neglected parasitic infections and socioeconomic factors in rural children of West Malaysia

Ngui R, Lim YA, Chong Kin L, Sek Chuen C, Jaffar S

PLoS Negl Trop Dis, 2012;6(3):e1550.
PMID: 22413027 DOI: 10.1371/journal.pntd.0001550

BACKGROUND: Given that micronutrient deficiency, neglected intestinal parasitic infections (IPIs) and poor socioeconomic status are closely linked, we conducted a cross-sectional study to assess the relationship between IPIs and nutritional status of children living in remote and rural areas in West Malaysia.
METHODS/FINDINGS: A total of 550 children participated, comprising 520 (94.5%) school children aged 7 to 12 years old, 30 (5.5%) young children aged 1 to 6 years old, 254 (46.2%) boys and 296 (53.8%) girls. Of the 550 children, 26.2% were anaemic, 54.9% iron deficient and 16.9% had iron deficiency anaemia (IDA). The overall prevalence of helminths was 76.5% comprising Trichuris trichiura (71.5%), Ascaris lumbricoides (41.6%) and hookworm infection (13.5%). It was observed that iron deficiency was significantly higher in girls (p = 0.032) compared to boys. Univariate analysis demonstrated that low level of mother's education (OR = 2.52; 95% CI = 1.38-4.60; p = 0.002), non working parents (OR = 2.18; 95% CI = 2.06-2.31; p = 0.013), low household income (OR = 2.02; 95% CI = 1.14-3.59; p = 0.015), T. trichiura (OR = 2.15; 95% CI = 1.21-3.81; p = 0.008) and A. lumbricoides infections (OR = 1.63; 95% CI = 1.04-2.55; p = 0.032) were significantly associated with the high prevalence of IDA. Multivariate analysis confirmed that low level of mother's education (OR = 1.48; 95 CI% = 1.33-2.58; p<0.001) was a significant predictor for IDA in these children.
CONCLUSION: It is crucial that a comprehensive primary health care programme for these communities that includes periodic de-worming, nutrition supplement, improved household economy, education, sanitation status and personal hygiene are taken into consideration to improve the nutritional status of these children.

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