The artificial introduction of the endosymbiotic bacterium, Wolbachia pipientis, into Aedes (Ae.) aegypti mosquitoes reduces the ability of mosquitoes to transmit human pathogenic viruses and is now being developed as a biocontrol tool. Successful introgression of Wolbachia-carrying Ae. aegypti into native mosquito populations at field sites in Australia, Indonesia and Malaysia has been associated with reduced disease prevalence in the treated community. In separate field programs, Wolbachia is also being used as a mosquito population suppression tool, where the release of male only Wolbachia-infected Ae. aegypti prevents the native mosquito population from producing viable eggs, subsequently suppressing the wild population. While these technologies show great promise, they require mass rearing of mosquitoes for implementation on a scale that has not previously been done. In addition, Wolbachia induces some negative fitness effects on Ae. aegypti. While these fitness effects differ depending on the Wolbachia strain present, one of the most consistent and significant impacts is the shortened longevity and viability of eggs. This review examines the body of evidence behind Wolbachia's negative effect on eggs, assesses nutritional parasitism as a key cause and considers how these impacts could be overcome to achieve efficient large-scale rearing of these mosquitoes.
In this article, data on the demographic parameters of the Aedes albopictus were collected from those areas in Shah Alam, Malaysia that had experienced a dengue outbreak. The surveys were conducted from March to December 2017. The eggs of the Ae. albopictus were collected using ovitraps, and were analysed based on the demographic parameters in a controlled environment in an insectarium. The data were comprised of four types of biological information on the life demographic parameters of the Ae. albopictus that were monitored based on specific localities. The data were inferred information regarding egg productivity (n), egg development (%), immature development (days), and survivorship (days).
Dengue is a viral infection caused by four types of viruses (DENV-1, DENV- 2, DENV-3, DENV-4) and transmitted through the bite of infected Aedes aegypti and Aedes albopictus female mosquitoes that feed both indoors and outdoors during the daytime (from dawn to dusk). These mosquitoes thrive in areas with standing water, including puddles, water tanks, containers and old tyres. There were a total of 35 dengue outbreaks under PKK KK with four active outbreaks in the year 2017. One uncontrolled outbreak occurred at Ibu Pejabat Kontigen (IPK) Kota Kinabalu from 16 November 2017 to 21 December 2017.
Dengue fever and dengue haemorrhagic fever are diseases caused by dengue virus transmitted by Aedes mosquitoes. Dengue fever has caused a high rate of mortalities among Malaysians every year. Even though many campaigns had been conducted by the government to reduce dengue cases, the number of infected people in this country is still high. We conducted this survey to determine the status of dengue fever awareness among residents in Kuala Terengganu. For data collection, face-to-face interviews were conducted, and a questionnaire was administered. There were three categories of respondents, namely urban area residents, rural area residents and university students. Results showed that respondents across the three groups were knowledgeable regarding dengue fever issues and there was no significant difference between the three categories of respondents in the number of residents who had been involved in dengue awareness programmes. However, most of the respondents regarded the dengue awareness programmes as moderately effective and could be overcome if prevention efforts and approaches were being carried out on a continuous basis.
Field bioefficacy of residual-sprayed deltamethrin against Aedes vectors was evaluated in an urban residential area in Kuala Lumpur. The trial area consisted of single storey wood-brick houses and a block of flat. The houses were treated with outdoor residual spraying while the flat was used as an untreated control. Initial pre-survey using ovitrap surveillance indicated high Aedes population in the area. Deltamethrin WG was sprayed at a dosage of 25mg/m2 using a compression sprayer. The effectiveness of deltamethrin was determined by wall bioassay and ovitrap surveillance. The residual activity of 25mg/m2 deltamethrin was still effective for 6 weeks after treatment, based on biweekly bioassay results. Bioassay also indicated that both Aedes aegypti and Aedes albopictus were more susceptible on the wooden surfaces than on brick. Aedes aegypti was more susceptible than Ae. albopictus against deltamethrin. Residual spraying of deltamethrin was not very effective against Aedes in this study since the Aedes population in the study area did not reduce as indicated by the total number of larvae collected using the ovitrap (Wilcoxon Sign Test, p> 0.05). Further studies are required to improve the effectiveness of residual spraying against Aedes vectors.
Preventive fogging is defined as space spraying of insecticide against mosquitoes in order to prevent outbreak of mosquito borne infection. Despite provision of various preventive andcontrol activities against dengue and chikungunya infection by Ministry of Health Guideline, the detail on preventive fogging has not yet specified. However, this has been adopted by certain institutions as part of the routine strategies against dengue outbreak. A study on preventive fogging was conducted in one of the hostels in Universiti Putra Malaysia. The research was done for 16 weeks in which one routine fogging activity was done at the mid period of study. The main objectives of this study were to determine the effectiveness of preventive fogging activities against Aedes mosquitoes and to identify the distribution and abundance of Aedes mosquitoes in the area. Method: The fogging activity was carried out by the management staff as part of their preventive measures in the student hostels. Ovitrap was used as an indicator to monitor the impact of fogging activity and its continuous surveillance was monitored weekly. The ovitraps were placed indoors and outdoors. Species identification was carried out in the laboratory. The SPSS program was used to analyse the statistical data on the effectiveness of fogging activity. Larval count (indoors and outdoors) and ovitrap index (OI) readings were identified as ovitrap surveillance data for statistical analysis. Results: The results showed that Aedes albopictus was the only species of the genus Aedes found in this hostel. The area had been highly infested by Ae. Albopictus as indicated by high Ovitrap Index ranging between 48.33% to 90.00%. The mean (SD) of Ovitrap Index was reduced from 71.67% (12.73%) (before the preventive fogging), to 69.42% (14.40%) (after the fogging). Overall reduction in mosquito and larval density was also observed between pre and post fogging activity in this study. Conclusion: The implementation of preventive fogging has favourably reduced the dengue vector population up to 5 weeks after the introduction of preventive fogging. However, sole dependency on preventive fogging may lead to insecticide resistance. Revisiting the policy on preventive fogging; and identifying it as an additional tool for preventing dengue infection in higher learning institutions are recommended.
A cross sectional survey was conducted in Kampung Datuk Kerarnat, an urbanized residential area in Kuala Lumpur from August to November ZOO5 to assess knowledge, attitude and preventive practices on dengue among its residents. A two stage sampling strategy was used to select survey household. An adult aged at least 21 years old was identified from each selected household and interviewed using a standardized questionnaire. Data was collected on demographics, dengue related KAP and house-types. Knowledge, attitude and practice were assessed using a scoring system. Each appropriate answer was given a point and the points for each section of the questionnaire were totalled. Knowledge was assessed as ‘good' or ‘moderate to poor’ based on arbitrary cut-off point. Out of 133 respondents interviewed, 78.2% were able to identify at least one clinical sign of dengue, 73% knew that dengue fever was caused by the bite of dengue infected Aedes mosquitoes, 71 % correctly identified breeding sites, 69.2% correctly identified the Aedes mosquito and 42% correctly reported biting times ofthe mosquito vector. Overall, knowledge
was categorized as poor, attitude was good and dengue control and prevention practices was moderately poor. There was a weak but significant positive correlation between knowledge and practice (r=0.271, p=0.002) but there was no significant correlation between attitude with practice and between attitude with knowledge (p>0.05) . The results suggested that inspite of good attitude l
on dengue fever, it did not correlate with good practices and good knowledge in dengue prevention. We conclude that there is a need to increase health promotion activities to increase knowledge which forms the basis for preventive practices as part of the strategy to control dengue. Preventive strategies are the only means of controlling the disease.
Background: The COMBI concept is a novel approach by the WHO to control communicable diseases which are influenced by community behaviour. The Ministry of Health is currently evaluating its use against dengue in selected areas throughout Malaysia. COMBI doctrine differs from previous dengue campaigns. It acknowledges that the factors contributing to dengue proliferation may differ between areas. Factors for a given area are analysed, then a single precise behavioural goal to overcome those problems is formulated. To inculcate this behavioural change, the target community is subjected to an intensive campaign using Integrated Marketing Communication techniques adapted from the advertisingindustry, particularly involving volunteers from the community itself.
Methodology: In Selangor the pilot project was implemented in Section 3 and Section 4 of Bandar Baru Bangi, in the district of Hulu Langat. Here, Aedes breeding was found to occur mainly in water containers of semi permanent nature (eg. ‘kolah’, aquatic plant jars, flower pot bases etc). A total of 172 volunteers were recruited to disperse the message of “Suluh – Suluh, Basuh - Basuh” whilst distributing leaflets and flashlights to 2666 homes. Residents were instructed to illuminate such water containers twice weekly and scrub any containers found to contain larvae. The program commenced on 23/5/2004 and lasted 16 weeks.
Results : During this period, the initial Aedes Index of 5 was reduced to 0.96 while combined cases of Dengue Fever / Dengue Haemorraghic Fever in Sections 3 and 4 reported to the Hulu Langat District Health Office also dropped to 1 (unconfirmed).
Conclusion : The COMBI approach in Hulu Langat successfully demonstrated that correct problem identification synergized with community engagement can potentially reduce Aedes proliferationand dengue morbidity.
Dengue is a serious mosquito borne disease common in tropical and sub-tropical countries including Malaysia. There is at present a lack of specific treatment and an effective tetravalent vaccine against dengue. The control of dengue depends solely on the suppression of the two most important vectors namely, Aedes aegypti and Ae albopictus. Despite intensive and extensive control efforts by health agencies, the disease continues to spread. This paper updates various innovations on control of dengue vectors. Gene-based sterile insect technique using the RIDL technology for both Aedes aegypti & Ae albopictus control has now been actively researched and field trials are pursued to evaluate the effectiveness of the technology. The release of Wolbachia-infected Ae aegypti is another dengue control innovation. The infected mosquito cannot support development of dengue virus and has shorter life span. Other innovations include: auto-dissemination of insect control agents using ovitrap, autocidal adult and larva trap, outdoor residual spraying, insecticidal paint and biocontrol agent. In other innovation, outbreak prediction capability is enhanced by developing model based on environmental data and analysis utilising neural network.
A preliminary field study was undertaken to evaluate the efficacy of a mosquito trap; Mosquito Killing System (MKS) in
capturing mosquitoes and other insects. MKS has an automatic activation by the use of a photocell. It is also supplemented
with carbon dioxide and heat as attractants for mosquitoes and other insects. Three units of MKS were employed at three
different locations within two study sites for ten days. The mosquitoes and other insects that were trapped in MKS were
collected and morphologically identified daily in the laboratory. A total of 1,928 mosquitoes and other insects were
trapped in all units of MKS. High numbers of mosquitoes (93.05%), particularly Aedes sp. and Culex sp. were captured
from MKS. Among these, Culex quinquefasciatus (91.81%) was most abundant species collected. Only 0.84% of Aedes
aegypti and Aedes albopictus trapped in MKS. Female mosquitoes (83.44%) were found to be more attracted to MKS
compared to male mosquitoes of various species. These findings illustrated the potency of MKS utilization in surveillance
and control activities of Cx. quinquefasciatus; a nuisance mosquito and also potential vector of urban brancroftian
filariasis in Malaysia.
Aedes aegypti and Aedes albopictus are the principle dengue vectors in Malaysia. The presence and distribution of Aedes larvae were studied in three different localities in Kelantan, Terengganu and Sabah, Malaysia in October 2008, November 2008 and June 2009. Two hundred (200) ovitraps per locality were placed randomly indoors and outdoors, depending on the environment of each locality. The highest mean number of Ae. aegypti and Ae. albopictus larvae per recovered ovitrap for both indoors and outdoors was obtained from Kg. Paya Rambai, Kelantan. The indoor populations of Ae. aegypti as well as the indoor and outdoor populations of Ae. albopictus in Kg. Paya Rambai, Kelantan were significantly higher than the other two study sites (p<0.05) by 1.03- and 4.67-folds, 2.36- and 5.84-folds and 1.98- and 4.00-folds, respectively. Both Ae. aegypti and Ae. albopictus were also found to breed within the same ovitraps placed indoors and outdoors in all study sites ranging from 15.22% to 31.82% of the total positive ovitraps. This study showed that both species could serve as the vectors of dengue in all study sites as indicated by the high populations recorded. The reliability and sensitivity of ovitraps in Aedes surveillance was also proven.
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.
Classification of Aedes aegypti (Linnaeus) and Aedes albopictus (Skuse) by humans remains challenging. We proposed a highly accessible method to develop a deep learning (DL) model and implement the model for mosquito image classification by using hardware that could regulate the development process. In particular, we constructed a dataset with 4120 images of Aedes mosquitoes that were older than 12 days old and had common morphological features that disappeared, and we illustrated how to set up supervised deep convolutional neural networks (DCNNs) with hyperparameter adjustment. The model application was first conducted by deploying the model externally in real time on three different generations of mosquitoes, and the accuracy was compared with human expert performance. Our results showed that both the learning rate and epochs significantly affected the accuracy, and the best-performing hyperparameters achieved an accuracy of more than 98% at classifying mosquitoes, which showed no significant difference from human-level performance. We demonstrated the feasibility of the method to construct a model with the DCNN when deployed externally on mosquitoes in real time.
Yearly, huge amounts of sock refuse are discarded into the environment. Socks contain many molecules, and worn ones, which are rich in smell-causing bacteria, have a strong influence on animals' behaviors. But the impacts of sock odor on the oviposition behavior of dengue vectors are unknown. We assessed whether Aedes albopictus changes its oviposition activity in response to the presence of used socks extract (USEx) in potential breeding grounds, using choice and no-choice bioassays (NCB). When furnished even chances to oviposit in two sites holding USEx and two others containing water (control), Ae. albopictus deposited significantly less eggs in USEx than in water sites. A similar pattern of oviposition preference was also observed when there were more oviposition options in water. When there were greater oviposition opportunities in USEx sites, Ae. albopictus oviposited preferentially in water. Females laid significantly more eggs during the NCB involving water than USEx. Also, significantly more mature eggs were retained by females in the NCB with USEx than in that with water. These observations strongly suggest the presence of molecules with either repellent or deterrent activities against Ae. albopictus females and provide an impetus to advocate the integration of used socks in dengue control programs. Such applications could be a realistic end-of-life recourse to reroute this waste from landfills.
Control of Aedes albopictus, major dengue and chikungunya vector, is threatened by growing cases of insecticide resistance. The mechanisms driving this resistance remain poorly characterised. This study investigated the molecular basis of insecticide resistance in Malaysian populations of Ae. albopictus. Microarray-based transcription profiling revealed that metabolic resistance (cytochrome P450 up-regulation) and possibly a reduced penetration mechanism (consistent over-expression of cuticular protein genes) were associated with pyrethroid resistance. CYP6P12 over-expression was strongly associated with pyrethroid resistance whereas CYP6N3 was rather consistently over-expressed across carbamate and DDT resistant populations. Other detoxification genes also up-regulated in permethrin resistant mosquitoes included a glucuronosyltransferase (AAEL014279-RA) and the glutathione-S transferases GSTS1 and GSTT3. Functional analyses further supported that CYP6P12 contributes to pyrethroid resistance in Ae. albopictus as transgenic expression of CYP6P12 in Drosophila was sufficient to confer pyrethroid resistance in these flies. Furthermore, molecular docking simulations predicted CYP6P12 possessing enzymatic activity towards pyrethroids. Patterns of polymorphism suggested early sign of selection acting on CYP6P12 but not on CYP6N3. The major role played by P450 in the absence of kdr mutations suggests that addition of the synergist PBO to pyrethroids could improve the efficacy of this insecticide class and overcome resistance in field populations of Ae. albopictus.
Dengue is a neglected disease caused by the infection of dengue virus which is transmitted by Aedes mosquitoes and to some, it could be fatal. Regardless of the enormous work devoted to research for the treatment of dengue, to this day there is no cure, and treatment is solely limited to supportive care by treating the symptoms. The inhibition of the viral RNA non-structural enzymes has been the most popular approach amongst the strategies applied to the search and development of dengue antivirals. This review is a compact digest of what is already known of the roles and the prospects of the dengue virus non-structural proteins NS1, NS2BNS3, NS4A, NS4B and NS5 as the targets for antiviral studies including the recent progress that has been published regarding their roles.
The author reviews the distribution, epidemiology, and treatment of filarial infection due to Brugia malayi, with special reference to Malaya. B. malayi infection in man is confined to the Far East between longitudes 75 degrees E and 140 degrees E and is essentially rural. The chief vectors are Mansonia spp., Anopheles hyrcanus group, A. barbirostris group, and Aëdes togoi. The epidemiological picture is complicated by the fact that B. malayi and other closely related species have now been found in several species of animals. The existence of an animal reservoir of infection might have important implications for filariasis control. As to the treatment of B. malayi infection, diethylcarbamazine has been found to reduce the microfilaria count and to kill the adult worms; the severe febrile reactions of microfilaria carriers to the initial doses of this drug may be reduced by administration of the steroid prednisolone.
Chikungunya virus (CHIKV) is an alphavirus of the Togaviridae family that causes chronic and incapacitating arthralgia in human populations. Since its discovery in 1952, CHIKV was responsible for sporadic and infrequent outbreaks. However, since 2005, global Chikungunya outbreaks have occurred, inducing some fatalities and associated with severe and chronic morbidity. Chikungunya is thus considered as an important re-emerging public health problem in both tropical and temperate countries, where the distribution of the Aedes mosquito vectors continues to expand. This review highlights the most recent advances in our knowledge and understanding of the epidemiology, biology, treatment and vaccination strategies of CHIKV.
The WHO adult susceptibility test is in use for insecticide resistance monitoring. Presently, materials are being imported from the Universiti Sains Malaysia, Malaysia and sometimes it is cost prohibitive. As an alternative, we present here a method of bottle bioassay using indigenous material. Different aspects related to the assay were studied and validated in the field. Bottle assay was standardized in the laboratory by using locally sourced material and laboratory-maintained insecticide-susceptible Anopheles stephensi and Aedes aegypti strains against technical grade deltamethrin and cyfluthrin insecticides dissolved in ethanol in a range of different concentrations. The frequency of use of the deltamethrin-coated bottles and shelf-life were determined. Discriminating dose for deltamethrin and cyfluthrin was 10 μg against An. stephensi and 2 μg against Ae. aegypti females. Insecticide-coated bottles stored at 25 to 35 °C can be used for three exposures within 7 days of coating. The study carried out in the laboratory was validated on wild caught An. culicifacies in the states of Odisha and Chhattisgarh against deltamethrin-coated bottles in comparison to WHO adult susceptibility test. Results of the study indicated that deltamethrin-coated bottles were effective up to three exposures within 7 days of coating for field population and 100% mortality was recorded within 35 min as observed in laboratory studies for field collected susceptible population. Also in the WHO adult susceptibility test, 100% knock-down within 35 min and 100% mortality after 24 h holding period were observed in susceptible population, while in it was 50% knock-down in 1 h and 64% mortality after 24 h holding period for resistant population (50% mortality in bottle assay in 60 min). The bottle assay can be used as an alternative to the WHO adult susceptibility test both in the laboratory and field for monitoring insecticide resistance in mosquito vectors using locally sourced material.
Dengue fever is a debilitating and infectious disease that could be life-threatening. It is caused by the dengue virus which affects millions of people in the tropical area. Currently, there is no cure for the disease as there is no vaccine available. Thus, prevention of the vector population using conventional methods is by far the main strategy but has been found ineffective. A genetically modified (GM) mosquito is among the favoured alternatives to curb dengue fever in Malaysia. Past studies have shown that development and diffusion of gene technology products depends heavily upon public acceptance. The purpose of this study is to identify the relevant factors influencing stakeholders' attitudes toward the GM Aedes mosquito and to analyse the relationships between all the factors using the structural equation model. A survey was carried out on 509 respondents from various stakeholder groups in the Klang Valley region of Malaysia. Results of the survey have confirmed that public perception towards complex issues such as gene technology should be seen as a multi-faceted process. The perceived benefit-perceived risk balance is very important in determining the most predominant predictor of attitudes toward a GM mosquito. In this study the stakeholders perceived the benefit of the GM mosquito as outweighing its risk, translating perceived benefit as the most important direct predictor of attitudes toward the GM mosquito. Trust in key players has a direct influence on attitudes toward the GM mosquito while moral concern exhibited an indirect influence through perceived benefits. Other factors such as attitudes toward technology and nature were also indirect predictors of attitudes toward the GM mosquito while religiosity and engagement did not exhibited any significant roles. The research findings serve as a useful database to understand public acceptance and the social construct of public attitudes towards the GM mosquito to combat dengue.