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Fulltext Measuring the effectiveness of integrated vector management with targeted outdoor residual spraying and autodissemination devices on the incidence of dengue in urban Malaysia in the iDEM trial (intervention for Dengue Epidemiology in Malaysia): study protocol for a cluster randomized controlled trial

Saadatian-Elahi M, Alexander N, Möhlmann T, Langlois-Jacques C, Suer R, Ahmad NW, et al.

Trials, 2021 May 30;22(1):374.
PMID: 34053466 DOI: 10.1186/s13063-021-05298-2

BACKGROUND: In common with many South East Asian countries, Malaysia is endemic for dengue. Dengue control in Malaysia is currently based on reactive vector management within 24 h of a dengue case being reported. Preventive rather than reactive vector control approaches, with combined interventions, are expected to improve the cost-effectiveness of dengue control programs. The principal objective of this cluster randomized controlled trial is to quantify the effectiveness of a preventive integrated vector management (IVM) strategy on the incidence of dengue as compared to routine vector control efforts.
METHODS: The trial is conducted in randomly allocated clusters of low- and medium-cost housing located in the Federal Territory of Kuala Lumpur and Putrajaya. The IVM approach combines: targeted outdoor residual spraying with K-Othrine Polyzone, deployment of mosquito traps as auto-dissemination devices, and community engagement activities. The trial includes 300 clusters randomly allocated in a 1:1 ratio. The clusters receive either the preventive IVM in addition to the routine vector control activities or the routine vector control activities only. Epidemiological data from monthly confirmed dengue cases during the study period will be obtained from the Vector Borne Disease Sector, Malaysian Ministry of Health e-Dengue surveillance system. Entomological surveillance data will be collected in 12 clusters randomly selected from each arm. To measure the effectiveness of the IVM approach on dengue incidence, a negative binomial regression model will be used to compare the incidence between control and intervention clusters. To quantify the effect of the interventions on the main entomological outcome, ovitrap index, a modified ordinary least squares regression model using a robust standard error estimator will be used.
DISCUSSION: Considering the ongoing expansion of dengue burden in Malaysia, setting up proactive control strategies is critical. Despite some limitations of the trial such as the use of passive surveillance to identify cases, the results will be informative for a better understanding of effectiveness of proactive IVM approach in the control of dengue. Evidence from this trial may help justify investment in preventive IVM approaches as preferred to reactive case management strategies.
TRIAL REGISTRATION: ISRCTN ISRCTN81915073 . Retrospectively registered on 17 April 2020.

Matched MeSH terms: Disease Vectors
Fulltext Report of the 2018 annual meeting of the Asia Pacific Malaria Elimination Network Vector Control Working Group: harnessing skills and knowledge for malaria elimination across the Asia Pacific

Dahmash L, Tatarsky A, Espino FE, Chareonviriyaphap T, Macdonald MB, Prachumsri JS, et al.

Parasit Vectors, 2021 May 29;14(1):290.
PMID: 34051831 DOI: 10.1186/s13071-021-04778-3

The 2018 Asia Pacific Malaria Elimination Network's Vector Control Working Group (APMEN VCWG) annual meeting took place 3-5 September 2018 in Bangkok, Thailand. It was designed to be a forum for entomology and public health specialists from APMEN country programmes (over 90 participants from 30 countries) to discuss current progress and challenges related to planning, implementing, and sustaining effective vector control (VC) strategies for malaria elimination across the region, and to suggest practical and applicable solutions to these moving forward. The meeting was organised as a joint collaboration between the VCWG host institution-Faculty of Tropical Medicine, Mahidol University, Thailand-and leading partner institutions within the VCWG: Malaria Consortium and the Malaria Elimination Initiative at the University of California, San Francisco, Global Health Group (UCSF Global Health Group), under the leadership of the APMEN Director and VCWG Co-Chairs from ministries of health in Malaysia and India. This report provides an introduction to the role and nature of the VCWG, highlights key themes and topics presented and discussed at the meeting, and outlines the future objectives and focal areas for the VCWG and APMEN at large.

Matched MeSH terms: Disease Vectors
Shifts in mosquito diversity and abundance along a gradient from oil palm plantations to conterminous forests in Borneo

Young KI, Buenemann M, Vasilakis N, Perera D, Hanley KA

Ecosphere, 2021 Apr;12(4).
PMID: 33996190 DOI: 10.1002/ecs2.3463

Deforestation precipitates spillover of enzootic, vector-borne viruses into humans, but specific mechanisms for this effect have rarely been investigated. Expansion of oil palm cultivation is a major driver of deforestation. Here, we demonstrate that mosquito abundance decreased over ten stepwise distances from interior forest into conterminous palm plantations in Borneo. Diversity in interior plantation narrowed to one species, Aedes albopictus, a potential bridge vector for spillover of multiple viruses. A. albopictus was equally abundant across all distances in forests, forest-plantation edge, and plantations, while A. niveus, a known vector of sylvatic dengue virus, was found only in forests. A. albopictus collections were significantly female-biased in plantation but not in edge or forest. Our data reveal that the likelihood of encountering any mosquito is greater in interior forest and edge than plantation, while the likelihood of encountering A. albopictus is equivalent across the gradient sampled from interior plantation to interior forest.

Matched MeSH terms: Disease Vectors
Fulltext Implications of the COVID-19 Lockdown on Dengue Transmission in Malaysia

Ong SQ, Ahmad H, Mohd Ngesom AM

Infect Dis Rep, 2021 Feb 05;13(1):148-160.
PMID: 33562890 DOI: 10.3390/idr13010016

We aim to investigate the effect of large-scale human movement restrictions during the COVID-19 lockdown on both the dengue transmission and vector occurrences. This study compared the weekly dengue incidences during the period of lockdown to the previous years (2015 to 2019) and a Seasonal Autoregressive Integrated Moving Average (SARIMA) model that expected no movement restrictions. We found that the trend of dengue incidence during the first two weeks (stage 1) of lockdown decreased significantly with the incidences lower than the lower confidence level (LCL) of SARIMA. By comparing the magnitude of the gradient of decrease, the trend is 319% steeper than the trend observed in previous years and 650% steeper than the simulated model, indicating that the control of population movement did reduce dengue transmission. However, starting from stage 2 of lockdown, the dengue incidences demonstrated an elevation and earlier rebound by four weeks and grew with an exponential pattern. We revealed that Aedes albopictus is the predominant species and demonstrated a strong correlation with the locally reported dengue incidences, and therefore we proposed the possible diffusive effect of the vector that led to a higher acceleration of incidence rate.

Matched MeSH terms: Disease Vectors
Fulltext Plasmodium-a brief introduction to the parasites causing human malaria and their basic biology

Sato S

J Physiol Anthropol, 2021 Jan 07;40(1):1.
PMID: 33413683 DOI: 10.1186/s40101-020-00251-9

Malaria is one of the most devastating infectious diseases of humans. It is problematic clinically and economically as it prevails in poorer countries and regions, strongly hindering socioeconomic development. The causative agents of malaria are unicellular protozoan parasites belonging to the genus Plasmodium. These parasites infect not only humans but also other vertebrates, from reptiles and birds to mammals. To date, over 200 species of Plasmodium have been formally described, and each species infects a certain range of hosts. Plasmodium species that naturally infect humans and cause malaria in large areas of the world are limited to five-P. falciparum, P. vivax, P. malariae, P. ovale and P. knowlesi. The first four are specific for humans, while P. knowlesi is naturally maintained in macaque monkeys and causes zoonotic malaria widely in South East Asia. Transmission of Plasmodium species between vertebrate hosts depends on an insect vector, which is usually the mosquito. The vector is not just a carrier but the definitive host, where sexual reproduction of Plasmodium species occurs, and the parasite's development in the insect is essential for transmission to the next vertebrate host. The range of insect species that can support the critical development of Plasmodium depends on the individual parasite species, but all five Plasmodium species causing malaria in humans are transmitted exclusively by anopheline mosquitoes. Plasmodium species have remarkable genetic flexibility which lets them adapt to alterations in the environment, giving them the potential to quickly develop resistance to therapeutics such as antimalarials and to change host specificity. In this article, selected topics involving the Plasmodium species that cause malaria in humans are reviewed.

Matched MeSH terms: Disease Vectors
Fulltext Genome-wide identification of Aedes albopictus long noncoding RNAs and their association with dengue and Zika virus infection

Azlan A, Obeidat SM, Theva Das K, Yunus MA, Azzam G

PLoS Negl Trop Dis, 2021 01;15(1):e0008351.
PMID: 33481791 DOI: 10.1371/journal.pntd.0008351

The Asian tiger mosquito, Aedes albopictus (Ae. albopictus), is an important vector that transmits arboviruses such as dengue (DENV), Zika (ZIKV) and Chikungunya virus (CHIKV). Long noncoding RNAs (lncRNAs) are known to regulate various biological processes. Knowledge on Ae. albopictus lncRNAs and their functional role in virus-host interactions are still limited. Here, we identified and characterized the lncRNAs in the genome of an arbovirus vector, Ae. albopictus, and evaluated their potential involvement in DENV and ZIKV infection. We used 148 public datasets, and identified a total of 10, 867 novel lncRNA transcripts, of which 5,809, 4,139, and 919 were intergenic, intronic and antisense respectively. The Ae. albopictus lncRNAs shared many characteristics with other species such as short length, low GC content, and low sequence conservation. RNA-sequencing of Ae. albopictus cells infected with DENV and ZIKV showed that the expression of lncRNAs was altered upon virus infection. Target prediction analysis revealed that Ae. albopictus lncRNAs may regulate the expression of genes involved in immunity and other metabolic and cellular processes. To verify the role of lncRNAs in virus infection, we generated mutations in lncRNA loci using CRISPR-Cas9, and discovered that two lncRNA loci mutations, namely XLOC_029733 (novel lncRNA transcript id: lncRNA_27639.2) and LOC115270134 (known lncRNA transcript id: XR_003899061.1) resulted in enhancement of DENV and ZIKV replication. The results presented here provide an important foundation for future studies of lncRNAs and their relationship with virus infection in Ae. albopictus.

Matched MeSH terms: Disease Vectors
Fulltext Cutaneous leishmaniasis-Awareness, knowledge and practices among general population in rural and urban areas in Malakand region, Pakistan

Khan W, Khan I, Ullah H, Zain SNM, Panhwar WA, Mehmood SA, et al.

Braz J Biol, 2021;82:e238665.
PMID: 33787717 DOI: 10.1590/1519-6984.238665

Malakand region is an endemic area for cutaneous leishmaniasis (CL). However, there are limited number of studies of this disease in Pakistan. Therefore, a study was conducted to understand the level of awareness attitude and practice among the residents of Makaland towards CL and the disease vectors. This study adopted a cross-sectional approach with a total of 400 respondents (n=93 rural and n= 307 urban). Overall, the population in Malakand region (61.2%) were well-informed in the role of sand fly in transmitting diseases, but most lack knowledge on the vector's behavior and almost a quarter (24.5%) were unable to provide knowledge on proper control measures. Alarmingly, the practice and attitudes of the general population was not satisfactory as close to half (49.8%) of the population did adopt any control method. This study calls for increase in awareness through health education campaign to reduce the risk of cutaneous leishmaniasis outbreaks in the future.

Matched MeSH terms: Disease Vectors
Dynamics of malaria vector indices in two vegetation zones within North Eastern Adamawa State, Nigeria

Wahedi JA, Ande AT, Oduola AO, Obembe A, Tola M, Oyeniyi TA, et al.

Trop Biomed, 2020 Sep 01;37(3):637-649.
PMID: 33612778 DOI: 10.47665/tb.37.3.637

Studies profiling community and zonal malaria entomological risk indices are required to identify high risk areas where targeted control resources are most needed or likely to have the greatest impact on reducing risk of malaria infection. This study presents a first report on malaria vector risk indices in two vegetation zones within Adamawa state, Nigeria. Endophilic mosquitoes were collected for one year in selected communities in the Guinea and Sudan savanna zones within the State. Plasmodium falciparum Sporozoite and human blood meal ELISA assays were carried out on the female Anopheles mosquitoes collected. Sibling species composition of the An. gambiae complex were determined using PCR assays. Mean numbers of mosquitoes in the Guinea savanna communities were significantly (t = 7.73, DF = 11, p < 0.001) higher than the Sudan. Man-biting rates (F = 2.76, p = 0.13) of Anopheles mosquitoes were higher in the Guinea but not significantly different from Sudan savanna. Sporozoite rates of mosquitoes within the Guinea savanna were 2.7 times higher than the Sudan. The predominant Anopheles coluzzii species encountered in the state had higher overall human blood indices (0.63) and sporozoite rates (6.9%) compared to An. gambiae (0.39, 1.9%) and An. arabiensis (0.58, 2.3%) respectively. Overall annual human blood indices (0.59) of mosquitoes in Adamawa were lower compared to reports from other States. Prevalence and higher transmission risks indices of endophilic An. coluzzii mosquitoes reveal the need for LLIN and management of relatively permanent An. coluzzii breeding sites in the State. Widespread cattle rearing lifestyle and lower human blood indices of mosquitoes in the study area suggest the need to investigate cattle blood indices of the mosquitoes in the state. Higher entomological risk indices in the Guinea Savanna zone provide baseline information for prioritization of malaria vector control supplies within the State.

Matched MeSH terms: Disease Vectors
Fulltext Seasonal Filarial Infections and Their Black Fly Vectors in Chiang Mai Province, Northern Thailand

Aupalee K, Saeung A, Srisuka W, Fukuda M, Streit A, Takaoka H

Pathogens, 2020 Jun 25;9(6).
PMID: 32630410 DOI: 10.3390/pathogens9060512

The transmission of zoonotic filarial parasites by black flies has so far been reported in the Chiang Mai and Tak provinces, Thailand, and the bites of these infected black flies can cause a rare disease-human zoonotic onchocerciasis. However, species identification of the filarial parasites and their black fly vectors in the Chiang Mai province were previously only based on a morphotaxonomic analysis. In this study, a combined approach of morphotaxonomic and molecular analyses (mitochondrial cox1, 12S rRNA, and nuclear 18S rRNA (SSU HVR-I) genes) was used to clarify the natural filarial infections in female black flies collected by using human and swine baits from two study areas (Ban Lek and Ban Pang Dang) in the Chiang Mai province from March 2018 to January 2019. A total of 805 and 4597 adult females, belonging to seven and nine black fly taxa, were collected from Ban Lek and Ban Pang Dang, respectively. At Ban Lek, four of the 309 adult females of Simulium nigrogilvum were positive for Onchocerca species type I in the hot and rainy seasons. At Ban Pang Dang, five unknown filarial larvae (belonging to the same new species) were detected in Simulium sp. in the S. varicorne species-group and in three species in the S. asakoae species-group in all seasons, and three non-filarial larvae of three different taxa were also found in three females of the S. asakoae species-group. This study is the first to molecularly identify new filarial species and their vector black fly species in Thailand.

Matched MeSH terms: Disease Vectors
Natural infections with larvae of Onchocerca species type I in the human-biting black fly, Simulium nigrogilvum (Diptera: Simuliidae), in western Thailand

Saeung A, Srisuka W, Aupalee K, Fukuda M, Otsuka Y, Taai K, et al.

Acta Trop, 2020 Apr;204:105344.
PMID: 31954685 DOI: 10.1016/j.actatropica.2020.105344

Zoonotic onchocerciasis is a human infection caused by Onchocerca species of animal origins and transmitted by black fly vectors. The reported incidence of this disease has increased throughout the world. This study aims to clarify the vectorial roles of black fly species in zoonotic filarial transmission in Tak province, western Thailand. The integrated approach of morphological and DNA sequence-based analyses was used to identify species of both wild-caught female black flies and infective filarial larvae found in the infected black flies. All of 494 female black flies captured were identified as Simulium nigrogilvum, through scanning electron microscopy (SEM) and DNA sequence analyses based on the cytochrome c oxidase subunit I (COI) and subunit II (COII), and the fast-evolving nuclear elongation complex protein 1 (ECP1) genes. Four females of S. nigrogilvum harbored one to three third-stage larvae (infective larvae) in their thoraces, with an infection rate of 0.81% (4/494). All infective larvae were similar in morphology and size to one another, being identified as Onchocerca species type I (= O. sp. type A), a bovine filaria, originally reported from Japan, and also as O. sp. found in S. nodosum in Thailand, based on their body lengths and widths being 1,068-1,346 µm long by 25-28 µm wide, and morphological characters. Comparisons of cytochrome c oxidase subunit I (COI) and 12S rRNA sequences of mitochondrial DNA (mtDNA) and phylogenetic analyses with those of previous reports strongly supported that all larvae were O. sp. type I. This report is the first indicating the presence of O. sp. type I in Thailand and its vector being S. nigrogilvum.

Matched MeSH terms: Disease Vectors
An overview of rickettsiae in Southeast Asia: Vector-animal-human interface

Low VL, Tan TK, Khoo JJ, Lim FS, AbuBakar S

Acta Trop, 2020 Feb;202:105282.
PMID: 31778642 DOI: 10.1016/j.actatropica.2019.105282

Rickettsioses are emerging, and re-emerging diseases caused by obligate intracellular arthropod-borne bacteria that infect humans and animals worldwide. Various rickettsiae such as Orientia, Rickettsia, Anaplasma and Ehrlichia have been circulated in companion, domesticated and wild animals through bites of infected ticks, fleas, lice or mites. This review summarizes the infections of rickettsiae, including the newly discovered regional species Rickettsia thailandii, Candidatus Rickettsia sepangensis, Candidatus Rickettsia johorensis, Candidatus Rickettsia laoensis, Candidatus Rickettsia mahosotii, Candidatus Rickettsia khammouanensis, Candidatus Anaplasma pangolinii, and other novel genotypes in vectors, humans and animals in Southeast Asia. Issues on some unidentified rickettsiae that elicit immune responses and production of antibodies that are cross-reactive with the antigens used are discussed. Knowledge gaps which required attention are also identified in this review.

Matched MeSH terms: Disease Vectors
Fulltext Aedestech mosquito home system prevents the hatch of Aedes mosquito eggs and reduces its population

Latifah Saiful Yazan, Paskaran, Kaveinesh, Gopalsamy, Banulata, Roslaini Abd Majid

Pertanika Journal of Science & Technology, 2020;28(1):263-278.
MyJurnal

Dengue fever (DF) is a global health problem and considered to be endemic in Malaysia. Conventional mosquito traps currently applied as vector control do not effectively reduce Aedes mosquito population. AedesTech Mosquito Home System (AMHS) is an autocidal ovitraps for Aedes mosquitoes that uses the ‘lure and kill’ concept and is expected to be able to reduce Aedes mosquito population. The effectiveness of AMHS in reducing Aedes mosquito population was investigated in Block A, B and D (control) of the 17th College, Universiti Putra Malaysia (UPM). For the first two weeks (pre-intervention), the conventional ovitraps were used to obtain the initial abundance of mosquito population in Block A, B and D. Subsequently, AMHS was used for the next three months and again followed by the conventional ovitrap for the final two weeks (post-intervention). Ovitrap Index, Hatching Index and percentage of emergence of adult mosquitoes were calculated once every two weeks. Data were analysed using Paired Sample T-test. Values were considered significant at p≤0.05. The Ovitrap Index that indicates the mosquito population at Block A and B was significantly higher (p≤0.05) than of Block D. Hatching Index of AMHS was significantly lower (p≤0.05) then conventional ovitraps. All mosquito eggs collected in AMHS did not develop into adult mosquitoes. There was a significant reduction (p≤0.05) in the mosquito population between the pre- and post-intervention. In conclusion, AMHS was effective in reducing the mosquito population in 17th College, UPM. Therefore, it is believed to be a very promising vector management option to control the incidence of DF.

Matched MeSH terms: Disease Vectors
Fulltext Host and environmental factors that influence Plasmodiu Knowlesi Mamlaria infection in humans: a systematic review

Michal Christina Steven

Borneo Epidemiology Journal, 2020;1(2):104-115.
MyJurnal

Introduction:Plasmodium knowlesi(P.knowlesi) is a zoonotic malaria parasite, transmitted between non-factors” or “individual factors” or “ecological factors” and “P.knowlesi” and “human” including human primate hosts by the Anopheles (An.) mosquitos, and causing spill-over infections in humans where the parasite, vector, host, and human converge
Methods:The search was done electronically toexplore for appropriate papers viaPubMed, and Science Direct for articles published up to March 2020, containing the words “factors associated” or “environmental synonyms and Medical Subject Heading (MeSH) terms. A total of 27 articles from PubMed Databases and 18 articles from Science Direct were selected to be assessed for eligibility. Out of it, a total of 13 articles were selected to be analysed.
Results:Host factors such as sex and age, as well as occupation as individual factors, while environmental factors such as rainfall and geographic elevation have some association with P.knowlesiinfection in humans. This zoonotic malaria poses unique challenges that will need to be addressed if all forms of malaria are to be eliminated based on the sustainable development goal (SDG)
Conclusion:This article highlights the importance of disease ecologies such as climate and landscape and human-environment interactions such as the land use patterns, such as agriculture or infrastructure activities) to reduce the further increase of cases and mortality globally due to P.knowlesiinfection. This review focuses mainly on the host and environmental factors that influence P.knowlesiMalaria Infection in Humans

Matched MeSH terms: Disease Vectors
Fulltext Wide area spray of bacterial larvicide, Bacillus thuringiensis israelensis strain AM65-52, integrated in the national vector control program impacts dengue transmission in an urban township in Sibu district, Sarawak, Malaysia

Bohari R, Jin Hin C, Matusop A, Abdullah MR, Ney TG, Benjamin S, et al.

PLoS One, 2020;15(4):e0230910.
PMID: 32236146 DOI: 10.1371/journal.pone.0230910

Several sites, Z-7L, Z-5 and Z-14, in Sibu district, Sarawak, Malaysia, experienced intense dengue transmission in 2014 that continued into 2015. A pilot study with Bacillus thuringiensis israelensis (Bti) to control Aedes aegypti (L.) and Ae. albopictus (Skuse) was evaluated in Z-7L, a densely populated site of 12 ha. Bti treatments were conducted weekly from epidemiology week (EW) 24/2015 for 4 weeks, followed by fortnight treatments for 2 months, in addition to the routine control activities. Bti was directly introduced into potable containers and the outdoor artificial and natural containers were treated via a wide area spray application method using a backpack mister. Aedes indices significantly reduced during the treatment and post treatment phases, compared to the control site, Z-5 (p<0.05). A 51 fold reduction in the incidence rate per 100,000 population (IR) was observed, with one case in 25 weeks (EW 29-52). In Z-5 and Z-14, control sites, a 6 fold reduction in the IR was observed from EW 29-52. However, almost every week there were dengue cases in Z-14 and until EW 44 in Z-5. In 2016, dengue cases resurfaced in Z-7L from EW 4. Intensive routine control activities were conducted, but the IR continued to escalate. The wide area Bti spray misting of the outdoor containers was then included from EW 27 on fortnight intervals. A 6 fold reduction in IR was observed in the Bti treatment phase (EW 32-52) with no successive weekly cases after EW 37. However, in the control sites, there were dengue cases throughout the year from EW 1-52, particularly in Z-14. We feel that the wide area Bti spray application method is an integral component in the control program, in conjunction with other control measures carried out, to suppress the vector population in outdoor cryptic containers and to interrupt the disease transmission.

Matched MeSH terms: Disease Vectors
Fulltext A Review of Quercus infectoria (Olivier) Galls as a Resource for Anti-parasitic Agents: In Vitro and In Vivo Studies

Zin NNINM, Rahimi WNAWM, Bakar NA

Malays J Med Sci, 2019 Nov;26(6):19-34.
PMID: 31908584 MyJurnal DOI: 10.21315/mjms2019.26.6.3

Parasitic diseases represent one of the causes for significant global economic, environmental and public health impacts. The efficacy of currently available anti-parasitic drugs has been threatened by the emergence of single drug- or multidrug-resistant parasite populations, vector threats and high cost of drug development. Therefore, the discovery of more potent anti-parasitic drugs coming from medicinal plants such as Quercus infectoria is seen as a major approach to tackle the problem. A systematic review was conducted to assess the efficacy of Q. infectoria in treating parasitic diseases both in vitro and in vivo due to the lack of such reviews on the anti-parasitic activities of this plant. This review consisted of intensive searches from three databases including PubMed, Science Direct and Scopus. Articles were selected throughout the years, limited to English language and fully documented. A total of 454 potential articles were identified, but only four articles were accepted to be evaluated based on inclusion and exclusion criteria. Although there were insufficient pieces of evidence to account for the efficacy of Q. infectoria against the parasites, this plant appears to have anti-leishmanial, anti-blastocystis and anti-amoebic activities. More studies in vitro and in vivo are warranted to further validate the anti-parasitic efficacy of Q. infectoria.

Matched MeSH terms: Disease Vectors
Fulltext Vector compositions change across forested to deforested ecotones in emerging areas of zoonotic malaria transmission in Malaysia

Hawkes FM, Manin BO, Cooper A, Daim S, R H, Jelip J, et al.

Sci Rep, 2019 09 16;9(1):13312.
PMID: 31527622 DOI: 10.1038/s41598-019-49842-2

In lowland areas of Malaysia, Plasmodium knowlesi infection is associated with land use change and high proportions of the vector Anopheles balabacensis. We conducted a 15-month study in two Malaysian villages to determine the effect of habitat on vector populations in understudied high-altitude, high-incidence districts. Anopheles mosquitoes were sampled in human settlements, plantations and forest edges, and screened for Plasmodium species by PCR. We report the first An. donaldi positive for P. knowlesi. This potential vector was associated with habitat fragmentation measured as disturbed forest edge:area ratio, while An. balabacensis was not, indicating fragmented land use could favour An. donaldi. Anopheline species richness and diversity decreased from forest edge, to plantation, to human settlement. Greater numbers of An. balabacensis and An. donaldi were found in forest edges compared to human settlements, suggesting exposure to vectors and associated zoonoses may be greater for people entering this habitat.

Matched MeSH terms: Disease Vectors/classification*
Genetic diversity of zoonotic malaria parasites from mosquito vector and vertebrate hosts

Wong ML, Ahmed MA, Sulaiman WYW, Manin BO, Leong CS, Quan FS, et al.

Infect Genet Evol, 2019 09;73:26-32.
PMID: 30999059 DOI: 10.1016/j.meegid.2019.04.010

We explored and constructed haplotype network for simian malaria species: Plasmodium knowlesi, P. cynomolgi and P. inui aiming to understand the transmission dynamics between mosquitoes, humans and macaques. Mosquitoes were collected from villages in an area where zoonotic malaria is prevalent. PCR analysis confirmed Anopheles balabacensis as the main vector for macaque parasites, moreover nearly 60% of the mosquitoes harboured more than one Plasmodium species. Fragments of the A-type small subunit ribosomal RNA (SS rRNA) amplified from salivary gland sporozoites, and equivalent sequences obtained from GenBank were used to construct haplotype networks. The patterns were consistent with the presence of geographically distinct populations for P. inui and P. cynomolgi, and with three discrete P. knowlesi populations. This study provides a preliminary snapshot of the structure of these populations, that was insufficient to answer our aim. Thus, collection of parasites from their various hosts and over time, associated with a systematic analysis of a set of genetical loci is strongly advocated in order to obtain a clear picture of the parasite population and the flow between different hosts. This is important to devise measures that will minimise the risk of transmission to humans, because zoonotic malaria impedes malaria elimination.

Matched MeSH terms: Disease Vectors
Who is biting you? DNA barcodes reveal cryptic diversity in human-biting black flies (Diptera: Simuliidae)

Jomkumsing P, Tangkawanit U, Wongpakam K, Pramual P

Acta Trop, 2019 Aug;196:22-29.
PMID: 31059708 DOI: 10.1016/j.actatropica.2019.05.001

Black flies (Simuliidae) are important biting insects and vectors of diseases agents of humans and livestock. Thus, understanding the taxonomy and biodiversity of these insects is crucial for control and management of these diseases. In this study, we used mitochondrial cytochrome c oxidase I sequences to examine genetic diversity of three human-biting and possible vector black fly taxa; the Simulium asakoae species-complex, S. chamlongi and S. nigrogilvum. High levels of genetic diversity (>3.5% intraspecific genetic divergence) were found in all three taxa. Phylogenetic analyses indicated that the S. asakoae complex can be divided into seven groups with the largest group consisting of specimens from Thailand, Malaysia and Myanmar. This group most likely represents true S. asakoae. The remaining haplotypes formed groups with conspecific haplotypes or with other closely related species. Among these groups, one including S. monglaense and another including S. myanmarense suggest that certain specimens identified as S. asakoae most likely belong to those species. Therefore, they constitute new locality records for Thailand and also represent new records of anthropophily. Members of S. chamlongi are not monophyletic as its clade also included S. hackeri. A median joining network revealed strong geographic associations of the haplotypes of S. nigrogilvum suggesting limitation of gene flow. Because this species occurs mainly in high elevation habitats, low land areas could present a barrier to gene flow.

Matched MeSH terms: Disease Vectors
Identification key to the genera of adult female mosquitoes (Diptera: Culicidae) of Singapore

Yeo H, Tan CH, Chong CS, Lam-Phua SG

Zootaxa, 2019 Jul 01;4624(3):zootaxa.4624.3.9.
PMID: 31716216 DOI: 10.11646/zootaxa.4624.3.9

Accurate identification of mosquitoes is crucial for the management and control of vector species. Although Singapore is a tropical country with high mosquito diversity, there are no identification keys specific to its mosquito fauna. An illustrated identification key to the genera of the adult female mosquitoes of Singapore is presented. Twenty genera are characterized and two genera found in Malaysia, Culiseta and Topomyia, are also included. The key will aid non-taxonomically trained operational officers in adult mosquito identification. The key to the genera provides the first crucial step in the process to species identification.

Matched MeSH terms: Disease Vectors
The electronic song "Scary Monsters and Nice Sprites" reduces host attack and mating success in the dengue vector Aedes aegypti

Dieng H, The CC, Satho T, Miake F, Wydiamala E, Kassim NFA, et al.

Acta Trop, 2019 Jun;194:93-99.
PMID: 30922800 DOI: 10.1016/j.actatropica.2019.03.027

Sound and its reception are crucial for reproduction, survival, and population maintenance of many animals. In insects, low-frequency vibrations facilitate sexual interactions, whereas noise disrupts the perception of signals from conspecifics and hosts. Despite evidence that mosquitoes respond to sound frequencies beyond fundamental ranges, including songs, and that males and females need to struggle to harmonize their flight tones, the behavioral impacts of music as control targets remain unexplored. In this study, we examined the effects of electronic music (Scary Monsters and Nice Sprites by Skrillex) on foraging, host attack, and sexual activities of the dengue vector Aedes aegypti. Adults were presented with two sound environments (music-off or music-on). Discrepancies in visitation, blood feeding, and copulation patterns were compared between environments with and without music. Ae. aegypti females maintained in the music-off environment initiated host visits earlier than those in the music-on environment. They visited the host significantly less often in the music-on than the music-off condition. Females exposed to music attacked hosts much later than their non-exposed peers. The occurrence of blood feeding activity was lower when music was being played. Adults exposed to music copulated far less often than their counterparts kept in an environment where there was no music. In addition to providing insight into the auditory sensitivity of Ae. aegypti to sound, our results indicated the vulnerability of its key vectorial capacity traits to electronic music. The observation that such music can delay host attack, reduce blood feeding, and disrupt mating provides new avenues for the development of music-based personal protective and control measures against Aedes-borne diseases.

Matched MeSH terms: Disease Vectors

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