Papers by Indra Vythilingam
Frontiers in Microbiology, Mar 21, 2023
The complex transmission profiles of vector-borne zoonoses (VZB) and vectorborne infections with ... more The complex transmission profiles of vector-borne zoonoses (VZB) and vectorborne infections with animal reservoirs (VBIAR) complicate efforts to break the transmission circuit of these infections. To control and eliminate VZB and VBIAR, insecticide application may not be conducted easily in all circumstances, particularly for infections with sylvatic transmission cycle. As a result, alternative approaches have been considered in the vector management against these infections. In this review, we highlighted differences among the environmental, chemical, and biological control approaches in vector management, from the perspectives of VZB and VBIAR. Concerns and knowledge gaps pertaining to the available control approaches were discussed to better understand the prospects of integrating these vector control approaches to synergistically break the transmission of VZB and VBIAR in humans, in line with the integrated vector management (IVM) developed by the World Health Organization (WHO) since 2004.
Tropical Biomedicine, Mar 1, 2019
Rickettsioses are a common health problem in many geographical areas, including rural areas in So... more Rickettsioses are a common health problem in many geographical areas, including rural areas in Southeast Asia. Co-infection of rickettsioses and malaria has been reported in Africa, where common reservoir and vectors are available. In this study, blood samples of Malaysian patients microscopically positive (n=148) and negative (n=88) for malaria parasites (Plasmodium knowlesi, Plasmodium malariae, Plasmodium falciparum, and Plasmodium vivax) were screened for the presence of rickettsial DNA, using PCR assays targeting specific genes. A partial fragment of rickettsial ompB gene was successfully amplified and sequenced from a patient microscopically positive for Plasmodium spp. and PCR-positive for P. vivax. BLAST analysis of the ompB sequence demonstrated the highest sequence similarity (99.7% similarity, 408/409nt) with Rickettsia sp. RF2125 (Genbank accession no. JX183538) and 91.4% (374/409 nt) similarity with Rickettsia felis URRWXCal2 (Genbank accession no. CP000053). This study reports rickettsial infection in a malaria patient for the first time in the Southeast Asia region.
PLOS Neglected Tropical Diseases, Aug 5, 2016
Geospatial Health, May 11, 2022
Dengue is a major mosquito-borne disease in many tropical and subtropical countries worldwide, wi... more Dengue is a major mosquito-borne disease in many tropical and subtropical countries worldwide, with entomological surveillance and control activities as the key management approaches. This study aimed to explore the spatial dispersal of the vector Aedes albopictus, captured by the modified sticky ovitrap (MSO) in residential areas with low-rise buildings in Selangor, Malaysia. Distribution maps were created and shown as temporally distinguished classes based on hotspot analysis by Getis-Ord; spatial autocorrelation assessed by semivariograms using the exponential Kernel function; and universal Kriging showing areas with estimated high and low vector densities. Distribution, hotspot and interpolated maps were analysed based on the total number of mosquitoes by month and week. All maps in the present study were generated and visualised in ArcMap. Spatial autocorrelation of Ae. albopictus based on the monthly occurrence of Ae. albopictus was found
International Journal of Tropical Insect Science, Feb 10, 2022
Dengue is a mosquito-borne disease that causes high mortality and fatality rate among humans. The... more Dengue is a mosquito-borne disease that causes high mortality and fatality rate among humans. The disease and the virus are spread through female Ae. aegypti and Ae. albopictus . 176 Modified Sticky Ovitraps (MSO) were installed in six blocks of high-rise apartment buildings in Petaling Jaya, Selangor. The specimens were collected throughout a duration of 26 weeks. NS1 dengue antigen kit was used to detect dengue antigen in mosquitoes, and positive mosquitoes were serotyped using Reverse Transcriptase-PCR, followed by Multiplex-PCR. The relationship between the number of Aedes mosquitoes and meteorological parameters was also determined. The association between the number of Aedes spp. captured, dengue cases, and positive specimens was also evaluated in this study. A total of 243 adult mosquitoes were successfully captured using MSO, with 95.1% (231) of the mosquitoes being Ae. aegypti , while 4.1% (10) and 0.8% (2) were Ae. albopictus and a mixed Aedes species, respectively. The molecular detection of the dengue virus showed that only 2 individual specimens of Ae. aegypti were positive, with one specimen being a dual serotype of DEN-II and IV, and another specimen was DENV-II. The weekly number of Aedes spp. captured correlated positively with Tmax, Tmin, and Tmean, and correlated negatively with RF and RH. The significant and useful data obtained from this study can be utilized in dengue vector management by local health authorities.
Journal of The American Mosquito Control Association, Jun 1, 2020
The present study aimed to explore the current status of knowledge and practices of dengue preven... more The present study aimed to explore the current status of knowledge and practices of dengue prevention associated with sociodemographic status among the community living in an urban area of Selangor, Malaysia. A total of 441 participants were interviewed regarding sociodemographic status, knowledge of dengue, and self-reported prevention practices. Participants over 40 years old were more likely (odds ratio [OR] ¼ 4.210, 95% CI ¼ 1.652-10.733, P ¼ 0.003) to have better dengue knowledge. Participants whose average monthly household income was more than MYR3,000 (US$715) were more likely (OR ¼ 1.607, 95% CI ¼ 1.059-2.438, P ¼ 0.026) to have better practices of dengue prevention measures. The finding suggests that both government and community efforts are essential in order to continue to educate about dengue and reduce the frequency of dengue cases nationwide.
Journal of Vector Ecology, Aug 1, 2022
International Journal of Infectious Diseases, May 1, 2023
Tropical Biomedicine, Oct 1, 2000
Tropical Biomedicine, Oct 1, 1997
International Journal of Tropical Insect Science, Mar 1, 2005
This note reports an unusual case of a high number of oocysts found by dissecting the midgut of A... more This note reports an unusual case of a high number of oocysts found by dissecting the midgut of Anopheles dirus Peyton & Harrison from Laos, where dissections have not been carried out for many decades. In dissected samples, the number of oocysts ranged from 1 to 250 and tests carried out on the heads and thoraces of A. dirus using the ELISA method were positive for Plasmodium falciparum.
PubMed, Mar 1, 1995
Detection and isolation of Japanese encephalitis (JE) virus were attempted from female mosquitoes... more Detection and isolation of Japanese encephalitis (JE) virus were attempted from female mosquitoes collected in Kampong Pasir Panjang, Sabak Bernam, Selangor, from May to November 1992. A total of 7,400 mosquitoes consisting of 12 species in 148 pools were processed and inoculated into Aedes albopictus clone C6/36 cell cultures. Of these, 26 pools showed the presence of viral antigens in the infected C6/36 cells by specific immunoperoxidase staining using an anti-JE virus polyclonal antibody. Presence of JE virus genome was confirmed in the infected culture fluid for 16 pools by using reverse transcriptase-polymerase chain reaction and JE virus-specific primers. Of these, 3 pools were from Culex tritaeniorhynchus, 4 from Culex vishnui, 3 from Culex bitaeniorhynchus, 2 from Culex sitiens, one from Aedes species, and 3 from Culex species. Isolation of JE virus from Cx. sitiens, Cx. bitaeniorhynchus, and Aedes sp. (Aedes butleri and Ae. albopictus) is reported for the first time in Malaysia.
PLOS Neglected Tropical Diseases
Background The elimination of malaria in Southeast Asia has become more challenging as a result o... more Background The elimination of malaria in Southeast Asia has become more challenging as a result of rising knowlesi malaria cases. In addition, naturally occurring human infections with other zoonotic simian malaria caused by Plasmodium cynomolgi and Plasmodium inui adds another level of complexity in malaria elimination in this region. Unfortunately, data on vectors which are responsible for transmitting this zoonotic disease is very limited. Methodology/Principal findings We conducted longitudinal studies to investigate the entomological parameters of the simian malaria vectors and to examine the genetic diversity and evolutionary pattern of their simian Plasmodium. All the captured Anopheles mosquitoes were dissected to examine for the presence of oocysts, sporozoites and to determine the parous rate. Our study revealed that the Anopheles Leucosphyrus Group mosquitoes are highly potential competent vectors, as evidenced by their high rate of parity, survival and sporozoite infecti...
Genes
Although Malaysia is considered free of human malaria, there has been a growing number of Plasmod... more Although Malaysia is considered free of human malaria, there has been a growing number of Plasmodium knowlesi cases. This alarming trend highlighted the need for our understanding of this parasite and its associated vectors, especially considering the role of genetic diversity in the adaptation and evolution among vectors in endemic areas, which is currently a significant knowledge gap in their fundamental biology. Thus, this study aimed to investigate the genetic diversity of Anopheles balabacensis, Anopheles cracens, Anopheles introlatus, and Anopheles latens—the vectors for P. knowlesi malaria in Malaysia. Based on cytochrome c oxidase 1 (CO1) and internal transcribed spacer 2 (ITS2) markers, the genealogic networks of An. latens showed a separation of the haplotypes between Peninsular Malaysia and Malaysia Borneo, forming two distinct clusters. Additionally, the genetic distances between these clusters were high (2.3–5.2% for CO1) and (2.3–4.7% for ITS2), indicating the likely p...
Insects
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
Background The simian malaria parasite Plasmodium knowlesi is emerging as a public health problem... more 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. Anophelesmosquitoes 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 vari-able 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 balabacen...
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Papers by Indra Vythilingam