MyMedR

Fulltext Seasonal and Spatial Dynamics of the Primary Vector of Plasmodium knowlesi within a Major Transmission Focus in Sabah, Malaysia

Wong ML, Chua TH, Leong CS, Khaw LT, Fornace K, Wan-Sulaiman WY, et al.

PLoS Negl Trop Dis, 2015;9(10):e0004135.

PMID: 26448052 DOI: 10.1371/journal.pntd.0004135

BACKGROUND: The simian malaria parasite Plasmodium knowlesi is emerging as a public health problem in Southeast Asia, particularly in Malaysian Borneo where it now accounts for the greatest burden of malaria cases and deaths. Control is hindered by limited understanding of the ecology of potential vector species.

METHODOLOGY/PRINCIPAL FINDINGS: We conducted a one year longitudinal study of P. knowlesi vectors in three sites within an endemic area of Sabah, Malaysia. All mosquitoes were captured using human landing catch. Anopheles mosquitoes were dissected to determine, oocyst, sporozoites and parous rate. Anopheles balabacensis is confirmed as the primary vector of. P. knowlesi (using nested PCR) in Sabah for the first time. Vector densities were significantly higher and more seasonally variable in the village than forest or small scale farming site. However An. balabacensis survival and P. knowlesi infection rates were highest in forest and small scale farm sites. Anopheles balabacensis mostly bites humans outdoors in the early evening between 1800 to 2000 hrs.

CONCLUSIONS/SIGNIFICANCE: This study indicates transmission is unlikely to be prevented by bednets. This combined with its high vectorial capacity poses a threat to malaria elimination programmes within the region.

Fulltext Modified technique of Wolbachia removal from Malaysian Aedes albopictus

Joanne S, Vythilingam I, Yugavathy N, Doss JI

Asian Pac J Trop Biomed, 2014 Jul;4(7):557-60.

PMID: 25183276 DOI: 10.12980/APJTB.4.2014APJTB-2014-0020

To develop an artificial and modified Wolbachia removal technique using tetracycline from naturally Wolbachia infected Aedes albopictus (Ae. albopictus) so as to be able to produce generations of Wolbachia free offsprings.

Pyrethroid resistance in Aedes aegypti larvae (Diptera: Culicidae) from Singapore

Koou SY, Chong CS, Vythilingam I, Ng LC, Lee CY

J Med Entomol, 2014 Jan;51(1):170-81.

PMID: 24605467

We report the first comprehensive insecticide susceptibility status ofAedes aegypti (L.) larvae from Singapore. The study indicated that Ae. aegypti is susceptible to temephos, although resistance (RR50 = 1.29-4.43-fold) couldbe developing. Of high concern is the detection of moderate to high resistance to permethrin (RR50 = 29-47-fold) and etofenprox (RR50 = 14-34-fold). Biolarvicide Bacillus thuringiensis israelensis (Bti) remains effective. The insecticide susceptibility profile of Ae. aegypti larvae was found to be homogenous among the different sites studied across the island city. The addition of synergists piperonyl butoxide, S,S,S,-tributyl phosphorotrithioate, and triphenyl phosphate generally failed to enhance the toxicity of the insecticides investigated, suggesting an insignificant role of metabolic-based resistance, and a possible involvement of target site resistance. Further biochemical investigation of specific metabolic enzyme activities suggested that detoxifying enzymes, mono-oxygenases, esterases, glutathione S-transferases, and altered acetylcholinesterases, generally did not contribute to the resistance observed. This study clearly demonstrated that pyrethroid resistance is widespread among Ae. aegypti population and lowered susceptibility to organophosphates is developing.

Fulltext Insecticide resistance and its underlying mechanisms in field populations of Aedes aegypti adults (Diptera: Culicidae) in Singapore

Koou SY, Chong CS, Vythilingam I, Lee CY, Ng LC

Parasit Vectors, 2014;7:471.

PMID: 25301032 DOI: 10.1186/s13071-014-0471-0

In Singapore, dose-response bioassays of Aedes aegypti (L.) adults have been conducted, but the mechanisms underlying resistance to insecticides remain unclear. In this study, we evaluated insecticide resistance and its underlying mechanism in field populations of Ae. aegypti adults.

Fulltext Plasmodium knowlesi malaria an emerging public health problem in Hulu Selangor, Selangor, Malaysia (2009-2013): epidemiologic and entomologic analysis

Vythilingam I, Lim YA, Venugopalan B, Ngui R, Leong CS, Wong ML, et al.

Parasit Vectors, 2014;7:436.

PMID: 25223878 DOI: 10.1186/1756-3305-7-436

While transmission of the human Plasmodium species has declined, a significant increase in Plasmodium knowlesi/Plasmodium malariae cases was reported in Hulu Selangor, Selangor, Malaysia. Thus, a study was undertaken to determine the epidemiology and the vectors involved in the transmission of knowlesi malaria.

Fulltext Increased detection of Plasmodium knowlesi in Sandakan division, Sabah as revealed by PlasmoNex™

Goh XT, Lim YA, Vythilingam I, Chew CH, Lee PC, Ngui R, et al.

Malar J, 2013 Jul 31;12:264.

PMID: 23902626 DOI: 10.1186/1475-2875-12-264

BACKGROUND: Plasmodium knowlesi is a simian malaria parasite that is widespread in humans in Malaysian Borneo. However, little is known about the incidence and distribution of this parasite in the Sandakan division, Malaysian Borneo. Therefore, the aim of the present epidemiological study was to investigate the incidence and distribution of P. knowlesi as well as other Plasmodium species in this division based on a most recent developed hexaplex PCR system (PlasmoNex™).

METHODS: A total of 189 whole blood samples were collected from Telupid Health Clinic, Sabah, Malaysia, from 2008 to 2011. All patients who participated in the study were microscopically malaria positive before recruitment. Complete demographic details and haematological profiles were obtained from 85 patients (13 females and 72 males). Identification of Plasmodium species was conducted using PlasmoNex™ targeting the 18S ssu rRNA gene.

RESULTS: A total of 178 samples were positive for Plasmodium species by using PlasmoNex™. Plasmodium falciparum was identified in 68 samples (38.2%) followed by 64 cases (36.0%) of Plasmodium vivax, 42 (23.6%) cases of P. knowlesi, two (1.1%) cases of Plasmodium malariae and two (1.1%) mixed-species infections (i e, P. vivax/P. falciparum). Thirty-five PlasmoNex™ positive P. knowlesi samples were misdiagnosed as P. malariae by microscopy. Plasmodium knowlesi was detected in all four districts of Sandakan division with the highest incidence in the Kinabatangan district. Thrombocytopaenia and anaemia showed to be the most frequent malaria-associated haematological complications in this study.

CONCLUSIONS: The discovery of P. knowlesi in Sandakan division showed that prospective studies on the epidemiological risk factors and transmission dynamics of P. knowlesi in these areas are crucial in order to develop strategies for effective malaria control. The availability of advanced diagnostic tool PlasmoNex™ enhanced the accuracy and accelerated the speed in the diagnosis of malaria.

Fulltext Colonization of Anopheles cracens: a malaria vector of emerging importance

Amir A, Sum JS, Lau YL, Vythilingam I, Fong MY

Parasit Vectors, 2013;6:81.

PMID: 23537404 DOI: 10.1186/1756-3305-6-81

Anopheles cracens has been incriminated as a vector for the simian malaria parasite, Plasmodium knowlesi, that is the fifth Plasmodium species infecting humans. Little experimental data exists on this mosquito species due to the lack of its availability in laboratories.

Fulltext Plasmodium knowlesi and Wuchereria bancrofti: Their Vectors and Challenges for the Future

Vythilingam I

Front Physiol, 2012;3:115.

PMID: 22557977 DOI: 10.3389/fphys.2012.00115

Malaria and filariasis still continue to pose public health problems in developing countries of the tropics. Although plans are in progress for the elimination of both these parasitic vector borne diseases, we are now faced with a daunting challenge as we have a fifth species, Plasmodium knowlesi a simian malaria parasite affecting humans. Similarly in peninsular Malaysia, filariasis was mainly due to Brugia malayi. However, we now see cases of Wuchereria bancrofti in immigrant workers coming into the country. In order to successfully eliminate both these diseases we need to know the vectors involved and introduce appropriate control measures to prevent the diseases occurring in the future. As for knowlesi malaria it is still uncertain if human to human transmission through mosquito bites is occurring. However, P. knowlesi in human is not a rare occurrence anymore and has all the characteristics of a pathogen spreading due to changes in the ecosystem, international travel, and cross border migration. This has created a more complex situation. In order to overcome these challenges we need to revamp our control measures. This paper reviews the vectors of malaria and filariasis in Southeast Asia with special emphasis on P. knowlesi and W. bancrofti in Malaysia and their control strategies.

Entomologic investigation of Plasmodium knowlesi vectors in Kuala Lipis, Pahang, Malaysia

Jiram AI, Vythilingam I, NoorAzian YM, Yusof YM, Azahari AH, Fong MY

Malar J, 2012;11:213.

PMID: 22727041

The first natural infection of Plasmodium knowlesi in humans was recorded in 1965 in peninsular Malaysia. Extensive research was then conducted and it was postulated that it was a rare incident and that simian malaria will not be easily transmitted to humans. However, at the turn of the 21st century, knowlesi malaria was prevalent throughout Southeast Asia and is life threatening. Thus, a longitudinal study was initiated to determine the vectors, their seasonal variation and preference to humans and macaques.

Fulltext Genotypic and phenotypic characterization of Chikungunya virus of different genotypes from Malaysia

Sam IC, Loong SK, Michael JC, Chua CL, Wan Sulaiman WY, Vythilingam I, et al.

PLoS One, 2012;7(11):e50476.

PMID: 23209750 DOI: 10.1371/journal.pone.0050476

Mosquito-borne Chikungunya virus (CHIKV) has recently re-emerged globally. The epidemic East/Central/South African (ECSA) strains have spread for the first time to Asia, which previously only had endemic Asian strains. In Malaysia, the ECSA strain caused an extensive nationwide outbreak in 2008, while the Asian strains only caused limited outbreaks prior to this. To gain insight into these observed epidemiological differences, we compared genotypic and phenotypic characteristics of CHIKV of Asian and ECSA genotypes isolated in Malaysia.

Fulltext Plasmodium knowlesi in humans: a review on the role of its vectors in Malaysia

Vythilingam I

Trop Biomed, 2010 Apr;27(1):1-12.

PMID: 20562807 MyJurnal

Plasmodium knowlesi in humans is life threatening, is on the increase and has been reported from most states in Malaysia. Anopheles latens and Anopheles cracens have been incriminated as vectors. Malaria is now a zoonoses and is occurring in malaria free areas of Malaysia. It is also a threat to eco-tourism. The importance of the vectors and possible control measures is reviewed here.

In vivo study of human Plasmodium knowlesi in Macaca fascicularis

Anderios F, Noorrain A, Vythilingam I

Exp Parasitol, 2010 Feb;124(2):181-9.

PMID: 19765587 DOI: 10.1016/j.exppara.2009.09.009

Plasmodium knowlesi is a malaria parasite of Old World monkeys and is infectious to humans. In this study Macaca fascicularis was used as a model to understand the host response to P. knowlesi using parasitological and haematological parameters. Three M. fascicularis of either sex were experimentally infected with P. knowlesi erythrocytic parasites from humans. The pre-patent period for P. knowlesi infection in M. fascicularis ranged from seven to 14 days. The parasitemia observed was 13,686-24,202 parasites per microL of blood for asexual stage and 88-264 parasites per microL of blood for sexual stage. Periodicity analysis adopted from microfilaria periodicity technique of asexual stage showed that the parasitemia peak at 17:39h while the sexual stage peaked at 02:36 h. Mathematical analysis of the data indicates that P. knowlesi gametocytes tend to display periodicity with a peak (24:00-06:00) that coincides with the peak biting activity (19:00-06:00) of the local vector, Anopheles latens. The morphology of P. knowlesi resembled P. falciparum in early trophozoite and P. malariae in late trophozoite. However, it may be distinguishable by observing the appliqué appearance of the cytoplasm and the chromatin lying inside the ring. Haematological analysis on macaques with knowlesi malaria showed clinical manifestations of hypoglycaemia, anaemia and hyperbilirubinemia. Gross examination of spleen and liver showed malaria pigments deposition in both organs.

Fulltext Plasmodium knowlesi malaria in Vietnam: some clarifications

Van den Eede P, Vythilingam I, Ngo DT, Nguyen VH, Le XH, D'Alessandro U, et al.

Malar J, 2010;9:20.

PMID: 20082717 DOI: 10.1186/1475-2875-9-20

A recently published comment on a report of Plasmodium knowlesi infections in Vietnam states that this may not accurately represent the situation in the study area because the PCR primers used may cross-hybridize with Plasmodium vivax. Nevertheless, P. knowlesi infections have been confirmed by sequencing. In addition, a neighbour-joining tree based on the 18S S-Type SSUrRNA gene shows that the Vietnamese samples clearly cluster with the P. knowlesi isolates identified in Malaysia and are distinct from the corresponding P. vivax sequences. All samples came from asymptomatic individuals who did not consult for fever during the months preceding or following the survey, indicating that asymptomatic P. knowlesi infections occur in this population, although this does not exclude the occurrence of symptomatic cases. Large-scale studies to determine the extent and the epidemiology of P. knowlesi malaria in Vietnam are further needed.

Fulltext Plasmodium knowlesi in humans, macaques and mosquitoes in peninsular Malaysia

Vythilingam I, Noorazian YM, Huat TC, Jiram AI, Yusri YM, Azahari AH, et al.

Parasit Vectors, 2008;1(1):26.

PMID: 18710577 DOI: 10.1186/1756-3305-1-26

Fulltext Bionomics of Anopheles latens in Kapit, Sarawak, Malaysian Borneo in relation to the transmission of zoonotic simian malaria parasite Plasmodium knowlesi

Tan CH, Vythilingam I, Matusop A, Chan ST, Singh B

Malar J, 2008;7:52.

PMID: 18377652 DOI: 10.1186/1475-2875-7-52

A large focus of human infections with Plasmodium knowlesi, a simian parasite naturally found in long-tailed and pig-tailed macaques was discovered in the Kapit Division of Sarawak, Malaysian Borneo. A study was initiated to identify the vectors of malaria, to elucidate where transmission is taking place and to understand the bionomics of the vectors in Kapit.

Fulltext Prevalence of intestinal protozoa in an aborigine community in Pahang, Malaysia

Noor Azian MY, San YM, Gan CC, Yusri MY, Nurulsyamzawaty Y, Zuhaizam AH, et al.

Trop Biomed, 2007 Jun;24(1):55-62.

PMID: 17568378 MyJurnal

The objective was to estimate the prevalence of intestinal protozoa among the aborigines and to determine the problems regarding the infection. The study was carried out in January 2006 in Pos Senderut, Pahang, Malaysia. Samples of faeces were collected from children and adults and these were fixed in PVA and trichrome staining was carried out. From the 130 individuals studied, 94 (72.3%) were positive with at least one intestinal protozoa. Nine intestinal protozoa namely Blastocystis hominis, Giardia lamblia, Entamoeba histolytica, Entamoeba coli, Endolimax nana, Entamoeba hartmani, Entamoeba polecki, Iodamoeba butschlii and Chilomastix mesnili were detected. The prevalent species were B. hominis (52.3%), followed by G. lamblia (29.2%), E. coli (26.2%) and E. histolytica (18.5%). The other species ranged from 1.5 to 10.8%. Among the positive samples, mixed infection with E. histolytica and G. lamblia was 3.8%, E. histolytica and B. hominis was 15.4%, G. lamblia and B. hominis was 17.7%. Triple infection of E. histolytica, G. lamblia and B. hominis was 3.1%. The infection was more prevalent in children below 10 years age group (45.4%) and lowest in the age above 60 years (3.8%). The high prevalence was attributable to poor environmental management, poor personal hygiene and lack of health education.

Natural transmission of Plasmodium knowlesi to humans by Anopheles latens in Sarawak, Malaysia

Vythilingam I, Tan CH, Asmad M, Chan ST, Lee KS, Singh B

Trans R Soc Trop Med Hyg, 2006 Nov;100(11):1087-8.

PMID: 16725166

Four species of malaria parasites are known to infect humans. A fifth species, Plasmodium knowlesi, has been reported to infect humans in Malaysian Borneo. Here we report for the first time the incrimination of Anopheles latens as the vector of P. knowlesi among humans and monkeys in Sarawak, Malaysia.

Species composition of mosquitoes of Attapeu Province, Lao People's Democratic Republic

Vythilingam I, Sidavong B, Thim CS, Phonemixay T, Phompida S, Jeffery J

J Am Mosq Control Assoc, 2006 Mar;22(1):140-3.

PMID: 16646338

A list of mosquitoes collected from Lao People's Democratic Republic (Lao PDR) from May 2002 to August 2004 is presented. A total of 8,945 mosquitoes belonging to 14 genera and 57 species was collected. The genera recorded were Aedes, Anopheles, Armigeres, Coquillettidia, Culex, Diceromyia, Downsiomyia, Fredwardsius, Mansonia, Neomelaniconion, Ochlerotatus, Paraedes, Stegomyia, and Verrallina. Seventeen species are first reports for LAO PDR.

Fulltext A comparative study of adult mosquito trapping using dry ice and yeast generated carbon dioxide

Oli K, Jeffery J, Vythilingam I

Trop Biomed, 2005 Dec;22(2):249-51.

PMID: 16883295 MyJurnal

Adult mosquito collections were conducted for 12 weeks in two residential areas in Kuala Lumpur. The CDC light traps were compared using dry ice and yeast as sources of carbon dioxide attractants for mosquitoes. The efficacy of the dry ice baited trap was significant over yeast generated CO2 trap. The predominant species obtained were Culex quinquefasciatus, Stegomyia albopicta and Armigeres subalbatus.

Epidemiology of malaria in Attapeu Province, Lao PDR in relation to entomological parameters

Vythilingam I, Sidavong B, Chan ST, Phonemixay T, Vanisaveth V, Sisoulad P, et al.

Trans R Soc Trop Med Hyg, 2005 Nov;99(11):833-9.

PMID: 16112154

Surveys were conducted in malaria-endemic villages in the southern province of Attapeu, Lao PDR during various seasons over a 3-year period. All-night mosquito landing collections, blood surveys and a case-control study were conducted. Plasmodium falciparum was the predominant species, and slide positivity rates were higher during the transition/dry season compared with the wet season. Anopheles dirus A was found to be the primary vector, and sporozoite rates were highest during the transition/dry season. Anopheles dirus was found to be endophagic and endophilic. Not using insecticide-treated bed nets, houses close to breeding sites and sleeping away from home were risk factors associated with malaria.

Displaying publications 61 - 80 of 110 in total