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Fulltext Rapid detection and identification of human hookworm infections through high resolution melting (HRM) analysis

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.
A Case of Zoonotic Ancylostoma ceylanicum Infection in a Suburban Area of Selangor, Malaysia

Heo CC, Rafiz AR, Ngui R

Acta Parasitol, 2021 Oct 06.
PMID: 34617193 DOI: 10.1007/s11686-021-00478-1

INTRODUCTION: The animal hookworm, Ancylostoma ceylanicum, is a dominant hookworm species of dogs and cats. However, it has increasingly been found infecting humans in Southeast Asia.
PURPOSE: We report an autochthonous case of A. ceylanicum in a suburban area of Selangor, Malaysia. A 66-year-old Indian lady who is an avid gardener presented with chronic diarrhea of 4 months' duration.
METHODS: The patient was examined clinically and colonoscopy was performed. Adult parasites obtained via colonoscopy were subjected to microscopy and molecular investigations.
RESULTS: Clinical examinations were unremarkable, and blood investigation revealed normochromic normocytic anemia. Stool occult blood was positive but negative for ova, cyst and adult parasites. Colonoscopy performed showed multiple diverticulae and worm infestation from the terminal ileum to sigmoid colon. Morphological examination on the adult worms showed the specific characteristics of Ancylostoma species. Molecular investigations further confirmed the nematode as Ancylostoma ceylanicum. She was treated with albendazole 400 mg daily for 3 days with symptomatic improvements sustained 3 months later. It is suspected that the patient had ingested or contacted soil contaminated with filariform larvae while gardening.
CONCLUSION: Information on the A. ceylanicum infection in humans, especially in urban and suburban areas, is limited, necessitating further epidemiological and clinical studies.
Serological and molecular detection of Strongyloides stercoralis infection among an Orang Asli community in Malaysia

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.
Fulltext Prevalence and risk factors of intestinal parasitism in rural and remote West Malaysia

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.
Fulltext Evaluation of sticky traps for adult Aedes mosquitoes in Malaysia: a potential monitoring and surveillance tool for the efficacy of control strategies

Roslan MA, Ngui R, Vythilingam I, Sulaiman WYW

J Vector Ecol, 2017 12;42(2):298-307.
PMID: 29125255 DOI: 10.1111/jvec.12270

The present study compared the performance of sticky traps in order to identify the most effective and practical trap for capturing Aedes aegypti and Aedes albopictus mosquitoes. Three phases were conducted in the study, with Phase 1 evaluating the five prototypes (Models A, B, C, D, and E) of sticky trap release-and-recapture using two groups of mosquito release numbers (five and 50) that were released in each replicate. Similarly, Phase 2 compared the performance between Model E and the classical ovitrap that had been modified (sticky ovitrap), using five and 50 mosquito release numbers. Further assessment of both traps was carried out in Phase 3, in which both traps were installed in nine sampling grids. Results from Phase 1 showed that Model E was the trap that recaptured higher numbers of mosquitoes when compared to Models A, B, C, and D. Further assessment between Model E and the modified sticky ovitrap (known as Model F) found that Model F outperformed Model E in both Phases 2 and 3. Thus, Model F was selected as the most effective and practical sticky trap, which could serve as an alternative tool for monitoring and controlling dengue vectors in Malaysia.
Fulltext Community surveillance of Aedes albopictus associated with Wolbachia detection in low-rise residential areas in Selangor, Malaysia

Roslan MA, Ngui R, Vythilingam I, Wan Sulaiman WY

J Vector Ecol, 2022 Dec;47(2):142-152.
PMID: 36314668 DOI: 10.52707/1081-1710-47.2.142

The study assessed the distribution of Malaysian Ae. albopictus adults associated with Wolbachia detection in low-rise residential areas using a modified sticky ovitrap (MSO). The relationship between Ae. albopictus and climatological parameters were also determined. Fifty-two weeks of surveillance using 273 MSOs were conducted in four installation areas of eleven sampling sites. Specimens were subjected to PCR using wsp-specific primers for Wolbachia detection. The relationship between climatological parameters and Ae. albopictus captured were analyzed using Spearman rank correlation coefficient test. The majority of Ae. albopictus were captured in residential houses (87%), followed by playgrounds or parks (11.5%), guardhouses (1%), and community halls (0.5%). Most of the specimens (92%) were superinfected with wAlbA and wAlbB strains. A positive correlation with no significant association was found for rainfall (r = 0.015, P = 0.072), relative humidity (r = 0.005, P = 0.526), minimum temperature (r = 0.005, P = 0.516), and mean temperature (r = 0.003, P = 0.689). MSO effectively captured a high number of Ae. albopictus that was determined to be the predominant mosquito species found in low-rise residential areas. The adult collection is not only influenced by climatological parameters but also by other factors, including environmental conditions and general sanitation status.
Fulltext Epidemiological and genetic data supporting the transmission of Ancylostoma ceylanicum among human and domestic animals

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.
Fulltext Expression of Ascaris lumbricoides putative virulence-associated genes when infecting a human host

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

Parasit Vectors, 2021 Mar 23;14(1):176.
PMID: 33757548 DOI: 10.1186/s13071-021-04680-y

BACKGROUND: Ascaris lumbricoides is the most common causative agent of soil-transmitted helminth infections worldwide, with an estimated 450 million people infected with this nematode globally. It is suggested that helminths are capable of evading and manipulating the host immune system through the release of a spectrum of worm proteins which underpins their long-term survival in the host. We hypothesise that the worm overexpresses these proteins when infecting adults compared to children to cirvumvent the more robust defence mechanisms of adults. However, little is known about the parasite's genes and encoded proteins involved during A. lumbricoides infection. Hence, this study was conducted to assess the expression profile of putative virulence-associated genes during an active infection of adults and children.
METHODS: In this study, quantitative PCR was performed to evaluate the expression profile of putative virulence-associated genes in A. lumbricoides isolated from infected children and adults. The study was initiated by collecting adult worms expelled from adults and children following anthelminthic treatment. High-quality RNA was successfully extracted from each of six adult worms expelled by three adults and three children, respectively. Eleven putative homologues of helminth virulence-associated genes reported in previous studies were selected, primers were designed and specific amplicons of A. lumbricoides genes were noted. The expression profiles of these putative virulence-associated genes in A. lumbricoides from infected adults were compared to those in A. lumbricoides from infected children.
RESULTS: The putative virulence-associated genes VENOM, CADHERIN and PEBP were significantly upregulated at 166-fold, 13-fold and fivefold, respectively, in adults compared to children. Conversely, the transcription of ABA-1 (fourfold), CATH-L (threefold) and INTEGRIN (twofold) was significantly suppressed in A. lumbricoides from infected adults.
CONCLUSIONS: On the basis of the expression profile of the putative virulence-associated genes, we propose that the encoded proteins have potential roles in evasion mechanisms, which could guide the development of therapeutic interventions.
Fulltext Antibody prevalence and factors associated with exposure to Orientia tsutsugamushi in different aboriginal subgroups in West Malaysia

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

BACKGROUND: 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.
METHODS/FINDINGS: The antibody prevalence to O. tsutsugamushi ranged from 0 to 36.4% in seven subgroups, with high prevalence rates noted in subgroups involved in agricultural activity and the lowest prevalence rates noted in subgroups whose main occupations were associated to fishing. Univariate analysis indicated populations with age above 18 years (OR = 1.15, 95% CI = 1.02-1.30, P = 0.015), working (OR = 1.99, 95% CI = 1.01-3.92, P = 0.044), working at agriculture area (OR = 1.18, 95% CI = 0.98-1.42, P = 0.031), receiving household income less than US$ 166.7 (RM500) per month (OR = 2.43, 95% CI = 1.16-5.11, P = 0.016) and having close contact with animal pets (OR = 4.06, 95% CI = 1.20-13.76, P = 0.016) are significantly associated with exposure to O. tsutsugamushi. Multivariate analysis confirms that participants who are above 18 years old, receiving household income less than US$ 166.7 (RM500) per month and having close contact with animal pets are 3.6 times (95% CI = 1.81-7.03, P<0.001), 1.3 times (95% CI = 1.14-1.64, P = 0.002) and 1.2 times (95% CI = 1.05-1.06, P = 0.006) more likely to have exposure to O. tsutsugamushi, respectively.
CONCLUSION: The present study indicates that scrub typhus is still an important disease in the aboriginal population in Malaysia. Awareness about the disease and education on the preventive measures are important in reducing the risk of acquiring scrub typhus in the population studied.
Fulltext Neglected tropical diseases among two indigenous subtribes in peninsular Malaysia: highlighting differences and co-infection of helminthiasis and sarcocystosis

Lee SC, Ngui R, Tan TK, Muhammad Aidil R, Lim YA

PLoS One, 2014;9(9):e107980.
PMID: 25248116 DOI: 10.1371/journal.pone.0107980

Soil-transmitted helminth (STH) infections have been documented among these minority groups since 1938. However the prevalence of STH is still high among these communities. Most studies tend to consider the Orang Asli (indigenous) as a homogenous group. In contrary, different subtribes have their own cultural practices. To understand this variation better, we studied the prevalence and associated factors of STH and other gut parasitic infections among two common subtribes (i.e. Temuan and Temiar). Results showed that the prevalence of the overall STH infections was higher in the Temuan subtribe (53.2% of 171) compared to the Temiar subtribe (52.7% of 98). Trichuris trichiura (46.2%) was the most prevalent parasite in the Temuan subtribe, followed by Ascaris spp. (25.7%) and hookworm (4.1%). In contrast, Ascaris spp. (39.8%) was more prevalent among the Temiar subtribe, preceded by T. trichiura (35.7%) and finally hookworm (8.3%). There were also co-infections of helminthiasis and intestinal protozoa among both Temuan and Temiar subtribes with rates being three times higher among the Temiar compared to Temuan. The most common co-infection was with Entamoeba histolytica/dispar/moshkovskii (n = 24; 24.5%, 16.0-33.0), followed by Giardia spp. (n = 3; 3.1%, -0.3-6.5). In Temuan, STH infection individuals were also infected with Entamoeba histolytica/dispar/moshkovskii (n = 11; 6.4%, 5.0-13.8), Cryptosporidium spp. (n = 3, 1.8%, -0.2-3.8) and Giardia spp. (n = 2, 1.2%, -0.4-2.8). In comparison, there was no Cryptosporidium spp. detected among the Temiar. However, it was interesting to note that there was an occurrence of co-infection of intestinal helminthiasis and sarcocystosis (intestinal) in a Temiar individual. The last report of sarcocystosis (muscular) among the Orang Asli was in 1978. The present study highlighted the importance of understanding the variation of infections amongst the different Orang Asli subtribes. It is vital to note these differences and use this knowledge to customise effective control measures for the various subtribes.
Fulltext Co-infection of Haemonchus contortus and Trichostrongylus spp. among livestock in Malaysia as revealed by amplification and sequencing of the internal transcribed spacer II DNA region

Tan TK, Panchadcharam C, Low VL, Lee SC, Ngui R, Sharma RS, et al.

BMC Vet Res, 2014;10:38.
PMID: 24502557 DOI: 10.1186/1746-6148-10-38

Haemonchus contortus and Trichostrongylus spp. are reported to be the most prevalent and highly pathogenic parasites in livestock, particularly in small ruminants. However, the routine conventional tool used in Malaysia could not differentiate the species accurately and therefore limiting the understanding of the co-infections between these two genera among livestock in Malaysia. This study is the first attempt to identify the strongylids of veterinary importance in Malaysia (i.e., H. contortus and Trichostrongylus spp.) by amplification and sequencing of the Internal Transcribed Spacer II DNA region.
Genetic characterization of the partial mitochondrial cytochrome oxidase c subunit I (cox 1) gene of the zoonotic parasitic nematode, Ancylostoma ceylanicum from humans, dogs and cats

Ngui R, Mahdy MA, Chua KH, Traub R, Lim YA

Acta Trop, 2013 Oct;128(1):154-7.
PMID: 23774318 DOI: 10.1016/j.actatropica.2013.06.003

Ancylostoma ceylanicum is the only zoonotic hookworm species that is able to produce patent infections in humans with the majority of cases reported in South East Asia. Over the past few years, there have been an increasing number of studies investigating the prevalence of this parasitic zoonosis using molecular diagnostic tools and a single genetic locus as marker for species identification. As there can be limitations in using a single genetic locus for epidemiological studies and genetic discrimination, the complementary use of a more variable locus will provide additional evidence to support the zoonotic exchange of hookworm species between humans and animals. In the present study, the cytochrome c oxidase subunit 1 (cox 1) sequence of A. ceylanicum from positive human and animal fecal samples were determined and compared with published reference sequences. Phylogenetic analysis demonstrated that isolates of A. ceylanicum were divided into two clusters, one consisting 3 human isolates and the other comprising 19 isolates of human and animal origin from different geographical locations within Malaysia. The two groups of A. ceylanicum could be distinguished from one another through five fixed nucleotide differences at locations 891, 966, 1008, 1077 and 1083. The detection of genetically distinct groups and considerable level of genetic variation within the cox 1 sequence of A. ceylanicum might suggest potential haplotype-linked differences in zoonotic, epidemiological and pathobiological characteristics, a hypothesis that still needs further investigation.
Differentiating Entamoeba histolytica, Entamoeba dispar and Entamoeba moshkovskii using nested polymerase chain reaction (PCR) in rural communities in Malaysia

Ngui R, Angal L, Fakhrurrazi SA, Lian YL, Ling LY, Ibrahim J, et al.

Parasit Vectors, 2012;5:187.
PMID: 22947430

In this study, a total of 426 human faecal samples were examined for the presence of Entamoeba histolytica, Entamoeba dispar, Entamoeba moshkovskii infection via a combination of microscopic examination and nested polymerase chain reaction (PCR) targeting 16S ribosomal RNA of Entamoeba species.
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.
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.

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