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Exposure of a diurnal mosquito vector to floral mimics: Foraging responses, feeding patterns, and significance for sugar bait technology

Dieng H, Satho T, Binti Arzemi NA, Aliasan NE, Abang F, Wydiamala E, et al.

Acta Trop, 2018 Sep;185:230-238.
PMID: 29856985 DOI: 10.1016/j.actatropica.2018.05.019

Food location by mosquitoes is mediated by resource-derived olfactory and visual signals. Smell sensation is intermittent and dependent on the environment, whereas visual signals are continual and precede olfactory cues. Success of mosquito bait technology, where olfactory cues are used for attraction, is being impeded by reduced attractiveness. Despite proof that mosquitoes respond to colored objects, including those mimicking floral shape, and that they can discriminate among flowers, the impacts of artificial flowers on foraging remain unexplored. Using artificial flowers with sugar rewards, we examined the foraging responses of Aedes aegypti to various colors in equal choice bioassays. Starved adults were exposed to single flowers with petals of a given color (Single Blue Flowers [SBFs]; Single Red Flowers [SRFs]; Single Yellow Flowers [SYFs]; Single Pink Flowers [SPIFs]; and Single Purple Flowers [SPFs]) and two others with white petals (SWFs). Discrepancies in response time, visitation, feeding, and resting of both sexes were compared between colored flowers and SWFs. Ae. aegypti exhibited shorter response times to colored flowers compared to SWFs, but this behavior was mostly seen for SBFs or SYFs in females, and SRFs, SYFs, SPIFs, or SPFs in males. When provided an option to land on colored flowers and SWFs, female visitation occurred at high rates on SBFs, SRFs, SYFs, SPIFs, and SPFs; for males, this preference for colored flowers was seen to a lesser degree on SBF and SPIFs. Both sexes exhibited preference for colored flowers as sugar sources, but with different patterns: SPIFs, SRFs, SYFs, and SPFs for females; SYFs, SPFs, SPIFs and SRFs for males. Females preferentially rested on colored flowers when in competition with SWFs, but this preference was more pronounced for SPFs, SRFs, and SBFs. Males exhibited an increased preference for SRFs, SPFs, and SYFs as resting sites. Our results indicated the attraction of Ae. aegypti to rewarding artificial flowers, in some cases in ways similar to live flowering plants. The discovery that both male and female Ae. aegypti can feed on nectar mimics held by artificial flowers opens new avenues for improving sugar bait technology and for developing new attract-and-kill devices.

Matched MeSH terms: Aedes/physiology*
Fulltext Effects of low-powered RF sweep between 0.01-20 GHz on female Aedes Aegypti mosquitoes: A collective behaviour analysis

Poh AH, Moghavvemi M, Shafiei MM, Leong CS, Lau YL, Mahamd Adikan FR, et al.

PLoS One, 2017;12(6):e0178766.
PMID: 28582398 DOI: 10.1371/journal.pone.0178766

There are many products claiming to be an electronic solution towards repelling mosquitoes. Several reviews were published in debunking these claims. However, there is a lack of a systematic study on effects of electromagnetic (EM) or more specifically, radio frequency (RF) waves against mosquitoes due to the conclusions made in those years. Therefore, we attempt to establish a fundamental study on female Aedes Aegypti (Linnaeus) mosquitoes by quantifying the collective behavior of the mosquitoes against a continuous stream of low-powered RF signals via a broadband horn antenna using image processing methods. By examining the average lateral and vertical positions of the mosquitoes versus frequency and time, the data shows negligible consistency in the reactions of the mosquitoes toward the different frequencies ranging from 10 to 20,000.00 MHz, with a step of 10 MHz. This was done by examining 33 hours of spatiotemporal data, which was divided into three sessions. All three sessions showed totally different convolutions in the positions in arbitrary units based on the raster scan of the image processing output. Several frequencies apparently showed up to 0.2-70% shift in both lateral and vertical components along the spectrum, without repeatability for all three sessions. This study contributes to the following: A pilot study for establishing the collective effects of RF against mosquitoes, open-source use, and finally a low-cost and easily adaptable platform for the study of EM effects against any insects.

Matched MeSH terms: Aedes/physiology*
Fulltext Development of a mechanistic dengue simulation model for Guangzhou

Mincham G, Baldock KL, Rozilawati H, Williams CR

Epidemiol Infect, 2019 01;147:e125.
PMID: 30869038 DOI: 10.1017/S095026881900030X

Dengue infection in China has increased dramatically in recent years. Guangdong province (main city Guangzhou) accounted for more than 94% of all dengue cases in the 2014 outbreak. Currently, there is no existing effective vaccine and most efforts of control are focused on the vector itself. This study aimed to evaluate different dengue management strategies in a region where this disease is emerging. This work was done by establishing a dengue simulation model for Guangzhou to enable the testing of control strategies aimed at vector control and vaccination. For that purpose, the computer-based dengue simulation model (DENSiM) together with the Container-Inhabiting Mosquito Simulation Model (CIMSiM) has been used to create a working dengue simulation model for the city of Guangzhou. In order to achieve the best model fit against historical surveillance data, virus introduction scenarios were run and then matched against the actual dengue surveillance data. The simulation model was able to predict retrospective outbreaks with a sensitivity of 0.18 and a specificity of 0.98. This new parameterisation can now be used to evaluate the potential impact of different control strategies on dengue transmission in Guangzhou. The knowledge generated from this research would provide useful information for authorities regarding the historic patterns of dengue outbreaks, as well as the effectiveness of different disease management strategies.

Matched MeSH terms: Aedes/physiology
Fulltext Biting rhythm and demographic attributes of Aedes albopictus (Skuse) females from different urbanized settings in Penang Island, Malaysia under uncontrolled laboratory conditions

Muhammad NAF, Abu Kassim NF, Ab Majid AH, Abd Rahman A, Dieng H, Avicor SW

PLoS One, 2020;15(11):e0241688.
PMID: 33175896 DOI: 10.1371/journal.pone.0241688

Urbanization could potentially modify Aedes albopictus' ecology by changing the dynamics of the species, and affecting their breeding sites due to environmental changes, and thus contribute to dengue outbreaks. Thus, this study was conducted to evaluate the biting rhythm, fecundity and longevity of adult female Ae. albopictus in relation to urbanization strata; urban, suburban and rural areas in Penang Island, Malaysia. The experiments were done in comparison to a laboratory strain. Twenty-four hours biting activity of all the mosquito strains showed a clear bimodal biting activity, with morning and evening twilight peaks. The interaction effect between biting time and mosquito strains was not significant. Meanwhile, differences in fecundity among mosquito strains were statistically significant (F(3,442) = 10.559, P < 0.05) with urban areas having higher mean number of eggs (mean = 107.69, standard error = 3.98) than suburban (mean = 94.48, standard error = 5.18), and rural areas (mean = 72.52, standard error = 3.87). Longevity of adult females were significantly higher (F(3,441) = 31.259, P < 0.05) for mosquito strains from urban areas compared to the other strains. These findings would provide crucial information for the planning of control programs in Malaysia, particularly Penang.

Matched MeSH terms: Aedes/physiology*
Spatio-temporal patterns of dengue in Malaysia: combining address and sub-district level

Ling CY, Gruebner O, Krämer A, Lakes T

Geospat Health, 2014 Nov;9(1):131-40.
PMID: 25545931

Spatio-temporal patterns of dengue risk in Malaysia were studied both at the address and the sub-district level in the province of Selangor and the Federal Territory of Kuala Lumpur. We geocoded laboratory-confirmed dengue cases from the years 2008 to 2010 at the address level and further aggregated the cases in proportion to the population at risk at the sub-district level. Kulldorff's spatial scan statistic was applied for the investigation that identified changing spatial patterns of dengue cases at both levels. At the address level, spatio-temporal clusters of dengue cases were concentrated at the central and south-eastern part of the study area in the early part of the years studied. Analyses at the sub-district level revealed a consistent spatial clustering of a high number of cases proportional to the population at risk. Linking both levels assisted in the identification of differences and confirmed the presence of areas at high risk for dengue infection. Our results suggest that the observed dengue cases had both a spatial and a temporal epidemiological component, which needs to be acknowledged and addressed to develop efficient control measures, including spatially explicit vector control. Our findings highlight the importance of detailed geographical analysis of disease cases in heterogeneous environments with a focus on clustered populations at different spatial and temporal scales. We conclude that bringing together information on the spatio-temporal distribution of dengue cases with a deeper insight of linkages between dengue risk, climate factors and land use constitutes an important step towards the development of an effective risk management strategy.

Matched MeSH terms: Aedes/physiology
Fulltext Indoor-breeding of Aedes albopictus in northern peninsular Malaysia and its potential epidemiological implications

Dieng H, Saifur RG, Hassan AA, Salmah MR, Boots M, Satho T, et al.

PLoS One, 2010;5(7):e11790.
PMID: 20668543 DOI: 10.1371/journal.pone.0011790

The mosquito Ae. albopictus is usually adapted to the peri-domestic environment and typically breeds outdoors. However, we observed its larvae in most containers within homes in northern peninsular Malaysia. To anticipate the epidemiological implications of this indoor-breeding, we assessed some fitness traits affecting vectorial capacity during colonization process. Specifically, we examined whether Ae. albopictus exhibits increased survival, gonotrophic activity and fecundity due to the potential increase in blood feeding opportunities.

Matched MeSH terms: Aedes/physiology*
Sterile mosquitoes near take-off

Cyranoski D

Nature, 2008 May 22;453(7194):435.
PMID: 18497781 DOI: 10.1038/453435a
Matched MeSH terms: Aedes/physiology*
ABSENCE OF AEDES AEGYPTI (L.) ON AN ECOLOGICAL ISLAND: COMPETITIVE EXCLUSION?

Afizah AN, Mahirah MN, Azahari AH, Asuad MK, Nazni WA, Lee HL

Southeast Asian J. Trop. Med. Public Health, 2015 Sep;46(5):850-6.
PMID: 26863856

Ovitrap surveillance was conducted in 2012 and 2006 in Malay and Aboriginal Villages on Carey Island. In each village, standard ovitraps were placed indoors and outdoors at randomly selected houses/locations. All L3 larvae recovered were identified up to species level. Results demonstrated that only larvae of Aedes albopictus were found in all the positive ovitraps placed indoors and outdoors. In 2012, a high ovitrap index (OI) of 66.7% indoor and 84.0% outdoor in the Malay Village; and 62.5% indoor and 88.0% outdoor in Aboriginal Village with an apparent absence of Aedes aegypti. In 2006, a 100% OI was recorded in all ovitraps set indoors and outdoors in both villages.

Matched MeSH terms: Aedes/physiology*
Fulltext Mosquitocidal and Oviposition Repellent Activities of the Extracts of Seaweed Bryopsis pennata on Aedes aegypti and Aedes albopictus

Yu KX, Wong CL, Ahmad R, Jantan I

Molecules, 2015;20(8):14082-102.
PMID: 26247928 DOI: 10.3390/molecules200814082

The ever-increasing threat from infectious diseases and the development of insecticide resistance in mosquito populations drive the global search for new natural insecticides. The aims of this study were to evaluate the mosquitocidal activity of the extracts of seaweed Bryopsis pennata against dengue vectors Aedes aegypti and Aedes albopictus, and determine the seaweed's toxic effect on brine shrimp nauplii (as a non-target organism). In addition, the chemical compositions of the active larvicidal extract and fraction were analyzed by using liquid chromatography-mass spectrometry (LC-MS). Chloroform extract exhibited strong ovicidal activity (with LC50 values of 229.3 and 250.5 µg/mL) and larvicidal activity against Ae. aegypti and Ae. albopictus. The larvicidal potential of chloroform extract was further ascertained when its A7 fraction exhibited strong toxic effect against Ae. aegypti (LC50 = 4.7 µg/mL) and Ae. albopictus (LC50 = 5.3 µg/mL). LC-MS analysis of the chloroform extract gave a tentative identification of 13 compounds; Bis-(3-oxoundecyl) tetrasulfide was identified as the major compound in A7 fraction. Methanol extract showed strong repellent effect against female oviposition, along with weak adulticidal activity against mosquito and weak toxicity against brine shrimp nauplii. The mosquitocidal results of B. pennata suggest further investigation for the development of effective insecticide.

Matched MeSH terms: Aedes/physiology*
Effect of ten chlorophytes on larval survival, development and adult body size of the mosquito Aedes aegypti

Ahmad R, Chu WL, Ismail Z, Lee HL, Phang SM

Southeast Asian J. Trop. Med. Public Health, 2004 Mar;35(1):79-87.
PMID: 15272748

The effect of ten microalgal chlorophytes isolated from mosquito breeding containers on the survival, larval development and adult body size of the mosquito Aedes aegypti was investigated. All larvae fed with six of the microalgal isolates died after 7 days. These isolates were found to be resistant to digestion by mosquito larvae. Delayed pupation and body size reduction of the mosquitos fed with Chlorococcum UMACC 218 and Scenedesmus UMACC 220 were observed. In contrast, larvae fed with Ankistrodesmus convolutus UMACC 101 and Chlorococcum UMACC 213 were bigger in size than those fed with normal insectory feed. The present study showed that microalgal chlorophytes have the potential to be used as larvicidal agents for mosquitos.

Matched MeSH terms: Aedes/physiology*
Fulltext Gravid oviposition sticky trap and dengue non-structural 1 antigen test for early surveillance of dengue in multi-storey dwellings: study protocol of a cluster randomized controlled trial

Liew JWK, Selvarajoo S, Tan W, Ahmad Zaki R, Vythilingam I

Infect Dis Poverty, 2019 Sep 03;8(1):71.
PMID: 31477185 DOI: 10.1186/s40249-019-0584-y

BACKGROUND: Dengue is a global disease, transmitted by the Aedes vectors. In 2018, there were 80 615 dengue cases with 147 deaths in Malaysia. Currently, the nationwide surveillance programs are dependent on Aedes larval surveys and notifications of lab-confirmed human infections. The existing, reactive programs appear to lack sensitivity and proactivity. More efficient dengue vector surveillance/control methods are needed.
METHODS: A parallel, cluster, randomized controlled, interventional trial is being conducted for 18 months in Damansara Damai, Selangor, Malaysia, to determine the efficacy of using gravid oviposition sticky (GOS) trap and dengue non-structural 1 (NS1) antigen test for early surveillance of dengue among Aedes mosquitoes to reduce dengue outbreaks. Eight residential apartments were randomly assigned into intervention and control arms. GOS traps are set at the apartments to collect Aedes weekly, following which dengue NS1 antigen is detected in these mosquitoes. When a dengue-positive mosquito is detected, the community will be advised to execute vector search-and-destroy and protective measures. The primary outcome concerns the the percentage change in the (i) number of dengue cases and (ii) durations of dengue outbreaks. Whereas other outcome measures include the change in density threshold of Aedes and changes in dengue-related knowledge, attitude and practice among cluster inhabitants.
DISCUSSION: This is a proactive and early dengue surveillance in the mosquito vector that does not rely on notification of dengue cases. Surveillance using the GOS traps should be able to efficiently provide sufficient coverage for multistorey dwellings where population per unit area is likely to be higher. Furthermore, trapping dengue-infected mosquitoes using the GOS trap, helps to halt the dengue transmission carried by the mosquito. It is envisaged that the results of this randomized controlled trial will provide a new proactive, cheap and targeted surveillance tool for the prevention and control of dengue outbreaks.
TRIAL REGISTRATION: This is a parallel-cluster, randomized controlled, interventional trial, registered at ClinicalTrials.gov (ID: NCT03799237), on 8th January 2019 (retrospectively registered).

Matched MeSH terms: Aedes/physiology*
Cold adaptation in the Asian tiger mosquito's native range precedes its invasion success in temperate regions

Sherpa S, Blum MGB, Després L

Evolution, 2019 09;73(9):1793-1808.
PMID: 31313825 DOI: 10.1111/evo.13801

Adaptation to environmental conditions within the native range of exotic species can condition the invasion success of these species outside their range. The striking success of the Asian tiger mosquito, Aedes albopictus, to invade temperate regions has been attributed to the winter survival of diapause eggs in cold environments. In this study, we evaluate genetic polymorphisms (SNPs) and wing morphometric variation among three biogeographical regions of the native range of A. albopictus. Reconstructed demographic histories of populations show an initial expansion in Southeast Asia and suggest that marine regression during late Pleistocene and climate warming after the last glacial period favored expansion of populations in southern and northern regions, respectively. Searching for genomic signatures of selection, we identified significantly differentiated SNPs among which several are located in or within 20 kb distance from candidate genes for cold adaptation. These genes involve cellular and metabolic processes and several of them have been shown to be differentially expressed under diapausing conditions. The three biogeographical regions also differ for wing size and shape, and wing size increases with latitude supporting Bergmann's rule. Adaptive genetic and morphometric variation observed along the climatic gradient of A. albopictus native range suggests that colonization of northern latitudes promoted adaptation to cold environments prior to its worldwide invasion.

Matched MeSH terms: Aedes/physiology*
Fulltext Surveillance of Aedes albopictus Skuse breeding preference in selected dengue outbreak localities, peninsular Malaysia

Rozilawati H, Tanaselvi K, Nazni WA, Mohd Masri S, Zairi J, Adanan CR, et al.

Trop Biomed, 2015 Mar;32(1):49-64.
PMID: 25801254 MyJurnal

Entomological surveillance was conducted in order to determine the abundance and to evaluate any changes of biological vectors or ecology, especially in the dengue outbreak areas. The abundance and breeding preference of Aedes albopictus and Aedes aegypti were conducted in selected dengue outbreak localities in three states of peninsular Malaysia namely Selangor, Federal Territory of Kuala Lumpur, and Penang Island using ovitraps and larval survey method. It was determined that Ae. albopictus was predominant in most of the localities and found to breed more outdoor than indoor. A wide range of breeding foci were recorded in this study. It was also determined that ovitrap method was more effective to detect the presence of Aedes mosquitoes when the larval survey was at low rate of infestation. The abundance of Ae. albopictus in dengue outbreak localities emphasis that the vector control programme should also target this species together with the primary dengue vector, Ae. aegypti.

Matched MeSH terms: Aedes/physiology*
Fulltext Influence of container design on predation rate of potential biocontrol agent, Toxorhynchites splendens (Diptera: Culicidae) against dengue vector

Mohamad N, Zuharah WF

Trop Biomed, 2014 Mar;31(1):166-73.
PMID: 24862057 MyJurnal

Toxorhynchites splendens larvae are a natural predator of dengue vector mosquito larvae, Aedes albopictus. This study was carried out to evaluate the predation rate of Tx. splendens third instar larvae on Ae. albopictus larvae in 24 h. Each predator was offered prey at a density between 10 to 50 individuals. Predation rate of Tx. splendens were also tested with two manipulated factors; various types of container and different water volumes. The experiment was evaluated in man-made containers (tin cans, plastic drinking glasses and rubber tires) and natural container (bamboo stumps) which were filled with different water volumes (full, half full, 1/4 full, and 1/8 full). The prey density and the characteristics of the container were found as significant factors which influence the predation rate of Tx. splendens. The predator consumed significantly more prey at higher prey densities (40 and 50 preys) compared to the lowest density (10 preys) (F=3.935, df=4, p=0.008). The results showed significantly higher consumption in horizontal shaped container of rubber tire than in vertical shape of bamboo stumps (F=3.100, df=3, p=0.029). However, the water volume had no significant effect on predation rate of Tx. splendens (F=1.736, df=3, p=0.162). We generally suggest that Tx. splendens is best to be released in discarded tires or any other containers with horizontal shape design with wide opening since Tx. splendens can become more effective in searching prey in this type of container design. This predator is also a suitable biocontrol candidates to be introduced either in wet and dry seasons in Malaysia.

Matched MeSH terms: Aedes/physiology*
Fulltext No evidence for successful interspecific cross-mating of transgenic Aedes aegypti (L.) and wild type Aedes albopictus Skuse

Lee HL, Aramu M, Nazni WA, Selvi S, Vasan S

Trop Biomed, 2009 Dec;26(3):312-9.
PMID: 20237445

The natural and artificial mating of laboratory bred Aedes albopictus and transgenic Aedes aegypti RIDL-513A-Malaysian strain was conducted. The experiment consisted of crossmating of homologous Ae. aegypti RIDL female symbol X Ae. aegypti RIDL male symbol and reciprocal Ae. aegypti RIDL female symbol X Ae. albopictus WT male symbol. The other set comprised homologous Ae. albopictus WT female symbol X Ae. albopictus WT male symbol and reciprocal Ae. albopictus WT female symbol X Ae. aegypti RIDL male symbol. This study demonstrated that reproductive barriers exist between these two species. Cross insemination occurred between A. albopictus male and Ae. aegypti female and their reciprocals. There was 26.67% and 33.33% insemination rate in Ae. aegypti RIDL female cross-mating with A. albopictus WT male and Ae. albopictus female cross-mating with Ae. aegypti RIDL male, respectively. There was 0% hatchability in both directions of the reciprocals. There was also no embryonation of these eggs which were bleached. Although none of the female Ae. albopictus WT was inseminated in the cross-mating with Ae. albopictus WT female symbol X Ae. aegypti RIDL male symbol, a total of 573 eggs were obtained. The homologous mating was very productive resulting in both high insemination rate and hatchability rates. Generally there was a significantly higher insemination rate with artificial mating insemination of homologous than with artificial mating of reciprocal crosses. Interspecific mating between Ae. aegypti RIDL and Ae. albopictus wild type was not productive and no hybrid was obtained, indicating absence of horizontal transfer of introduced RIDL gene in Ae. aegypti to Ae. albopictus.

Matched MeSH terms: Aedes/physiology*
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.

Matched MeSH terms: Aedes/physiology
Sweet waste extract uptake by a mosquito vector: Survival, biting, fecundity responses, and potential epidemiological significance

Dieng H, Satho T, Abang F, Meli NKKB, Ghani IA, Nolasco-Hipolito C, et al.

Acta Trop, 2017 May;169:84-92.
PMID: 28174057 DOI: 10.1016/j.actatropica.2017.01.022

In nature, adult mosquitoes typically utilize nectar as their main energy source, but they can switch to other as yet unidentified sugary fluids. Contemporary lifestyles, with their associated unwillingness to consume leftovers and improper disposal of waste, have resulted in the disposal of huge amounts of waste into the environment. Such refuse often contains unfinished food items, many of which contain sugar and some of which can collect water from rain and generate juices. Despite evidence that mosquitoes can feed on sugar-rich suspensions, semi-liquids, and decaying fruits, which can be abundant in garbage sites, the impacts of sweet waste fluids on dengue vectors are unknown. Here, we investigated the effects of extracts from some familiar sweet home waste items on key components of vectorial capacity of Aedes aegypti. Adult mosquitoes were fed one of five diets in this study: water (WAT); sucrose (SUG); bakery product (remnant of chocolate cake, BAK); dairy product (yogurt, YOG); and fruit (banana (BAN). Differences in survival, response time to host, and egg production were examined between groups. For both males and females, maintenance on BAK extract resulted in marked survival levels that were similar to those seen with SUG. Sweet waste extracts provided better substrates for survival compared to water, but this superiority was mostly seen with BAK. Females maintained on BAK, YOG, and BAN exhibited shorter response times to a host compared to their counterparts maintained on SUG. The levels of egg production were equivalent in waste extract- and SUG-fed females. The findings presented here illustrate the potential of sweet waste-derived fluids to contribute to the vectorial capacity of dengue vectors and suggest the necessity of readdressing the issue of waste disposal, especially that of unfinished sweet foods. Such approaches can be particularly relevant in dengue endemic areas where rainfall is frequent and waste collection infrequent.

Matched MeSH terms: Aedes/physiology*
Fulltext Global Epidemiology of Dengue Outbreaks in 1990-2015: A Systematic Review and Meta-Analysis

Guo C, Zhou Z, Wen Z, Liu Y, Zeng C, Xiao D, et al.

Front Cell Infect Microbiol, 2017;7:317.
PMID: 28748176 DOI: 10.3389/fcimb.2017.00317

Dengue is an arthropod-borne infectious disease caused by dengue virus (DENV) infection and transmitted byAedesmosquitoes. Approximately 50-100 million people are infected with DENV each year, resulting in a high economic burden on both governments and individuals. Here, we conducted a systematic review and meta-analysis to summarize information regarding the epidemiology, clinical characteristics, and serotype distribution and risk factors for global dengue outbreaks occurring from 1990 to 2015. We searched the PubMed, Embase and Web of Science databases through December 2016 using the term "dengue outbreak." In total, 3,853 studies were identified, of which 243 studies describing 262 dengue outbreaks met our inclusion criteria. The majority of outbreak-associated dengue cases were reported in the Western Pacific Region, particularly after the year 2010; these cases were primarily identified in China, Singapore and Malaysia. The pooled mean age of dengue-infected individuals was 30.1 years; of the included patients, 54.5% were male, 23.2% had DHF, 62.0% had secondary infections, and 1.3% died. The mean age of dengue patients reported after 2010 was older than that of patients reported before 2010 (34.0 vs. 27.2 years); however, the proportions of patients who had DHF, had secondary infections and died significantly decreased after 2010. Fever, malaise, headache, and asthenia were the most frequently reported clinical symptoms and signs among dengue patients. In addition, among the identified clinical symptoms and signs, positive tourniquet test (OR= 4.86), ascites (OR= 13.91) and shock (OR= 308.09) were identified as the best predictors of dengue infection, DHF and mortality, respectively (bothP< 0.05). The main risk factors for dengue infection, DHF and mortality were living with uncovered water container (OR= 1.65), suffering from hypotension (OR= 6.18) and suffering from diabetes mellitus (OR= 2.53), respectively (allP< 0.05). The serotype distribution varied with time and across WHO regions. Overall, co-infections were reported in 47.7% of the evaluated outbreaks, and the highest pooled mortality rate (2.0%) was identified in DENV-2 dominated outbreaks. Our study emphasizes the necessity of implementing programs focused on targeted prevention, early identification, and effective treatment.

Matched MeSH terms: Aedes/physiology
Fulltext Evaluation of resting traps to examine the behaviour and ecology of mosquito vectors in an area of rapidly changing land use in Sabah, Malaysian Borneo

Brown R, Hing CT, Fornace K, Ferguson HM

Parasit Vectors, 2018 Jun 14;11(1):346.
PMID: 29898780 DOI: 10.1186/s13071-018-2926-1

BACKGROUND: Widespread deforestation occurring in the tropics is hypothesized to impact the transmission of vector-borne diseases (VBD). Predicting how environmental changes will impact VBD transmission is dependent on understanding the ecology and behaviour of potential vector species outside of domestic settings. However there are few reliable sampling tools for measuring the habitat preference and host choice of mosquito vectors; with almost none suitable for sampling recently blood-fed, resting mosquitoes. This study evaluated the use of two mosquito traps: the resting bucket (RB) and sticky resting bucket (SRB) traps relative to CDC backpack aspiration (CDC) for sampling mosquitoes resting in a range of habitats representing a gradient of deforestation. Eight habitats were selected for sampling around two villages in Kudat District, Malaysian Borneo, to reflect the range of habitats available to mosquitoes in and around human dwellings, and nearby forest habitats where reservoir hosts are present: secondary forest (edge, interior and canopy); plantations (palm and rubber); and human settlements (inside, under and around houses).
RESULTS: Over 31 days, 2243 mosquitoes were collected in 5748 discrete collections. Nine mosquito genera were sampled with Aedes and Culex species being present in all habitats and most abundant. RB and CDC backpack aspiration were most efficient for sampling Culex whereas CDC backpack aspiration and SRB were most efficient for Aedes. Most Aedes identified to species level were Ae. albopictus (91%), with their abundance being highest in forest edge habitats. In contrast, Culex were most abundant under houses. Most blood-fed mosquitoes (76%) were found in human settlements; with humans and chickens being the only blood source.
CONCLUSIONS: RB and SRB traps proved capable of sampling mosquitoes resting in all sampled habitats. However, sampling efficiency was generally low (c.0.1 per trap per day), necessitating traps to be deployed in high numbers for mosquito detection. None of the traps were effective for sampling zoonotic malaria vectors; however, SRB collected relatively higher numbers of the dengue vector Ae. albopictus. The higher abundance of mosquitoes in forest edge habitats indicates the potential value of these traps for investigating sylvatic dengue transmission. This study has demonstrated the merits in application of simple resting traps for characterising mosquito vector resting behaviour outside of the home.

Matched MeSH terms: Aedes/physiology*
Fulltext An update on the mosquito fauna and mosquito-borne diseases distribution in Cameroon

Bamou R, Mayi MPA, Djiappi-Tchamen B, Nana-Ndjangwo SM, Nchoutpouen E, Cornel AJ, et al.

Parasit Vectors, 2021 Oct 11;14(1):527.
PMID: 34635176 DOI: 10.1186/s13071-021-04950-9

The expansion of mosquito-borne diseases such as dengue, yellow fever, and chikungunya in the past 15 years has ignited the need for active surveillance of common and neglected mosquito-borne infectious diseases. The surveillance should be designed to detect diseases and to provide relevant field-based data for developing and implementing effective control measures to prevent outbreaks before significant public health consequences can occur. Mosquitoes are important vectors of human and animal pathogens, and knowledge on their biodiversity and distribution in the Afrotropical region is needed for the development of evidence-based vector control strategies. Following a comprehensive literature search, an inventory of the diversity and distribution of mosquitoes as well as the different mosquito-borne diseases found in Cameroon was made. A total of 290 publications/reports and the mosquito catalogue website were consulted for the review. To date, about 307 species, four subspecies and one putative new species of Culicidae, comprising 60 species and one putative new species of Anopheles, 67 species and two subspecies of Culex, 77 species and one subspecies of Aedes, 31 species and one subspecies of Eretmapodites, two Mansonia, eight Coquillettidia, and 62 species with unknown medical and veterinary importance (Toxorhynchites, Uranotaenia, Mimomyia, Malaya, Hodgesia, Ficalbia, Orthopodomyia, Aedeomyia, and Culiseta and Lutzia) have been collected in Cameroon. Multiple mosquito species implicated in the transmission of pathogens within Anopheles, Culex, Aedes, Eretmapodites, Mansonia, and Coquillettidia have been reported in Cameroon. Furthermore, the presence of 26 human and zoonotic arboviral diseases, one helminthic disease, and two protozoal diseases has been reported. Information on the bionomics, taxonomy, and distribution of mosquito species will be useful for the development of integrated vector management programmes for the surveillance and elimination of mosquito-borne diseases in Cameroon.

Matched MeSH terms: Aedes/physiology

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