Aedes Pupae Research Articles

Mosquitocidal efficacy of embelin and its derivatives against Aedes aegypti L. and Culex quinquefasciatus Say. (Diptera: Culicidae) and computational analysis of acetylcholinesterase 1 (AChE1) inhibition

Embelin was isolated from the chloroform extract of Embelia ribes (Burm.f.) fruits; its derivative compounds 6-bromoembelin and vilangin were prepared, and they were evaluated for mosquitocidal activities against the third instar larvae and pupae of Aedes aegypti L. and Culex quinquefasciatus Say. (Diptera: Culicidae). The concentrations used were 0.5, 1.0, 1.5, and 2.0 ppm. Embelin recorded LC50 values of 5.79 and 5.54 ppm against the larvae of Ae. aegypti and Cx. quinquefasciatus, respectively. Similarly, the LC50 values of embelin were 10.23 and 6.93 ppm against the pupae of Ae. aegypti and Cx. quinquefasciatus, respectively. Of the two derivatives tested, vilangin showed the highest larvicidal activity with LC50 values of 1.38 and 1.28 ppm against the larvae of Ae. aegypti and Cx. quinquefasciatus, respectively. Similarly, the LC50 values of vilangin were 1.60 and 1.43 ppm against the pupae of Ae. aegypti and Cx. quinquefasciatus, respectively. The LC50 values of 6-bromoembelin were 3.30 and 2.83 ppm against the larvae and 4.40 and 4.30 ppm against the pupae of Ae. aegypti and Cx. quinquefasciatus, respectively. The histopathological results displayed significant damage on cuboidal cells of the midgut (CU) in vilangin treated larvae of Ae. aegypti and Cx. quinquefasciatus at a concentration of 2.0 ppm. Similarly, peritrophic membrane (PM) was completely impaired in vilangin-treated larvae of Cx. quinquefasciatus and midgut content (MC) was very low in vilangin-treated larvae of Cx. quinquefasciatus. In addition, molecular docking and molecular dynamics studies demonstrated the efficacy of vilangin on the inhibition of acetylcholinesterase (AChE1) in Ae. aegypti and Cx. quinquefasciatus. The present results suggest that vilangin could be used to develop a natural active product against mosquito larvae.

Mycosynthesis, Characterization, and Mosquitocidal Activity of Silver Nanoparticles Fabricated by Aspergillus niger Strain.

Herein, silver nanoparticles (Ag-NPs) were synthesized using an environmentally friendly approach by harnessing the metabolites of Aspergillus niger F2. The successful formation of Ag-NPs was checked by a color change to yellowish-brown, followed by UV-Vis spectroscopy, Fourier transforms infrared (FT-IR), Transmission electron microscopy (TEM), and X-ray diffraction (XRD). Data showed the successful formation of crystalline Ag-NPs with a spherical shape at the maximum surface plasmon resonance of 420 nm with a size range of 3–13 nm. The Ag-NPs showed high toxicity against I, II, III, and IV instar larvae and pupae of Aedes aegypti with LC50 and LC90 values of 12.4–22.9 ppm and 22.4–41.4 ppm, respectively under laboratory conditions. The field assay exhibited the highest reduction in larval density due to treatment with Ag-NPs (10× LC50) with values of 59.6%, 74.7%, and 100% after 24, 48, and 72 h, respectively. The exposure of A. aegypti adults to the vapor of burning Ag-NPs-based coils caused a reduction of unfed individuals with a percentage of 81.6 ± 0.5% compared with the positive control, pyrethrin-based coils (86.1 ± 1.1%). The ovicidal activity of biosynthesized Ag-NPs caused the hatching of the eggs with percentages of 50.1 ± 0.9, 33.5 ± 1.1, 22.9 ± 1.1, and 13.7 ± 1.2% for concentrations of 5, 10, 15, and 20 ppm, whereas Ag-NPs at a concentration of 25 and 30 ppm caused complete egg mortality (100%). The obtained data confirmed the applicability of biosynthesized Ag-NPs to the biocontrol of A. aegypti at low concentrations.

Biocontrol of Aedes aegypti using Talaromyces islandicus Synthesized Silver Nanoparticles

Aedes aegypti is the vector that spreads the dengue virus, causing dengue fever and dengue hemorrhagic fever. With more than half the world’s population at the risk of acquiring this infection, controlling the Aedes mosquitoes is the only path to limit the spread of the fatal disease. The emergence of insect resistance in mosquitoes raised the need for developing novel insecticides. Present research is focused on using fungus (Talaromyces islandicus) as the biosystem in the synthesis of nanoparticles. Myco-synthesized silver nanoparticles were characterized using UV-visible spectrometry that exhibited a peak at 429 nm. The XRD spectral peaks were in the range of 27.83º, 32.27º, 38.23º and 65.01º. The FTIR spectrum showed peaks corresponding to O-H, N-O, S=O, etc. representing the silver nanoparticles. SEM and EDAX represent the formation of silver ions that are spherical in shape with a size range of 23 to 26 nm. The antioxidant activity of silver nanoparticles and the extract of Talaromyces islandicus were assessed by DPPH assay, reducing power assay and hydrogen peroxide assay. The nanoparticles studied for its bio efficacy against the larval stages of Aedes aegypti indicated the LC50 value of 352.03, 389.86, 397.72 and 443.50 when tested against first, second, third and fourth instar larvae. respectively. The LC50 value of 540.41 was determined against the pupae of Aedes. The predatory efficiency of P. reticulata indicated the positive feeding behaviour of the fish when exposed to the silver nanoparticles. The cell toxicity assay was conducted against C6/36 insect cell lines and the cell viability inhibition was calculated. A toxic free, environmentally acceptable approach for controlling the mosquito vector by utilizing fungal nanoparticles was assessed and their efficacy in vector control was analyzed in this study.

Effects of gamma radiation on the reproductive viability of Aedes aegypti and its descendants (Diptera: Culicidae)

This work evaluated the genetic damage in descendants of male pupae of Aedes (Stegomyia) aegypti (Diptera: Culicidae) separately exposed to 20, 30, and 40 Gy of gamma radiation in the context of Sterile Insect Technique (SIT). Despite the transmission of the dominant lethal mutation, the employed dose levels did not promote a marked reduction in adult mosquito emergence and fertility. This study emphasized that semi-sterilizing doses < 50 Gy for SIT of Aedes aegypti are not recommended.

Effect of community-based intervention on awareness of dengue and its prevention among urban poor community in India: a systematic review approach

Owing to increased epidemic activity and difficulties in controlling the insect vector, dengue has become a major public health problem globally. The prevention and control of dengue rely mainly on vector control methods. A systematic review was conducted using four databases (PubMed, Cochrane, Google Scholar and Scopus) and a manual search of the reference lists of the identified studies. Data from included studies were extracted, analyzed. Applying all inclusion and exclusion criteria 23 articles was included. Further relevant articles using this keywords Aedes dengue breeding habits housing and community intervention were selected. Eight studies combined community participation programme with dengue control tools. Findings of the published literature indicate that at baseline, almost half the respondents did not know that dengue is serious but preventable, or that it is transmitted by mosquitoes. The analysis showed that dengue vector control is carried out by vertically structured programmes of national, state, and local administrative bodies through fogging and larval control, without any involvement of community-based organizations, and that vector control efforts were conducted in an isolated and irregular way. The most productive container types for Aedes pupae were cement tanks, drums, and discarded containers. Evidence that community-based dengue control programmes alone and in combination with other control activities can enhance the effectiveness of dengue control programmes is weak. This review demonstrates a paucity of reliable evidence for the effectiveness of any dengue vector control method. Standardized studies of higher quality to evaluate and compare methods must be prioritized to optimize cost-effective dengue prevention. Clear best practice guidelines for the methodology of entomological studies should be developed.

Ability of the Premise Condition Index to Identify Premises with Adult and Immature Aedes Mosquitoes in Kampong Cham, Cambodia.

.Aedes-transmitted diseases, especially dengue, are increasing throughout the world and the main preventive methods include vector control and the avoidance of mosquito bites. A simple Premise Condition Index (PCI) categorizing shade, house, and yard conditions was previously developed to help prioritize households or geographical areas where resources are limited. However, evidence about the accuracy of the PCI is mixed. The current study aimed to contribute to a better understanding of the relevance by collecting data from 2,400 premises at four time points over 1 year in Kampong Cham, Cambodia. Regression models were then used to identify associations between PCI and Aedes adult female mosquitoes and pupae. In addition, receiver operating characteristic curves were used to measure the ability of PCI to identify premises in the top quartile of mosquito abundance. The density of adult Aedes females was positively associated with PCI at the household (ratio of means = 1.16 per point on the PCI scale) and cluster level (ratio of means = 1.54). However, the number of Aedes pupae was negatively associated with PCI at the household level (rate ratio = 0.74) and did not have a statistically significant association at the cluster level. Receiver operating characteristic curves suggest the PCI score had “rather low accuracy” (area under the ROC curve = 0.52 and 0.54) at identifying top-quartile premises in terms of adult female Aedes and pupae, respectively. These results suggest that caution is warranted in the programmatic use of PCI in areas of similar geography and mosquito abundance.

Biological control of mosquito larvae using naiad of ruddy marsh skimmer Crocothemis servilia

The naiads of Crocothemis servilia (Drury) feed only on larvae of Culex quiniquefasciatus and both larvae and pupae of Aedes aegypti under laboratory condition. It prefers 2nd instar larva over other instars of C. quiniquefasciatus and for 3rd instar larvae of A. aegypti. These exhibited higher predation rate during day time. The diurnal clearance rate was significantly higher than the nocturnal one for both the species. Maximum clearance rate was observed during first hour of predation. Results indicate that C. servilia could be used as a potential biocontrol agent against mosquito larvae.

ANTIMICROBIAL, ANTIRADICAL AND INSECTICIDAL ACTIVITY OF GARDENIA GUMMIFERA L. F. (RUBIACEAE)

Objective: The present study was carried out to investigate antimicrobial, antiradical and insecticidal potential of leaf and fruit of Gardenia gummifera L. f. (Rubiaceae).Methods: The leaf and fruits were shade dried, powdered and extracted by maceration process using methanol. Antibacterial activity was evaluated against Gram positive and Gram negative bacteria by Agar well diffusion assay. Antifungal activity was determined against six seed-borne fungi by Poisoned food technique. Antiradical activity of leaf and fruit extracts was evaluated by 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2-azinobis 3-ethylbenzothiazoline 6-sulfonate (ABTS) radical scavenging assays. Insecticidal activity of leaf and fruit extracts, in terms of larvicidal and pupicidal activity, was assessed against larvae and pupae of Aedes aegypti.Results: Both the extracts inhibited all test bacteria. Marked antibacterial activity was displayed by fruit extract when compared to leaf extract. S. epidermidis and E. coli were inhibited to highest and least extent by both extracts respectively. Fruit extract was found to exhibit higher antifungal effect when compared to leaf extract. Leaf extract and fruit extract exhibited highest inhibitory activity against A. niger and A. flavus respectively. Leaf and fruit extracts scavenged DPPH radical’s dose dependently with an IC50 value of 49.01µg/ml and 2.53µg/ml respectively. The scavenging of ABTS by leaf and fruit extracts was dose dependent and the IC50 value for leaf and fruit extract was 2.58µg/ml and 2.31µg/ml respectively. Fruit extract was shown to exhibit marked antiradical activity when compared to leaf extract. Leaf and fruit extracts exhibited dose dependent insecticidal activity in terms of larvicidal and pupicidal activity and the susceptibility of larvae and pupae to extracts was in the order II instar larvae&gt;IV instar larvae&gt;pupae. Fruit extract displayed marked insecticidal potential when compared to leaf extract.Conclusion: Overall, fruit extract of G. gummifera exhibited marked antimicrobial, antiradical and insecticidal activity when compared to leaf extract. The plant can be used for developing agents/formulations effective against infectious microorganisms, oxidative stress and insect vectors that transmit dreadful diseases. The observed bioactivities could be ascribed to the presence of active principles which are to be isolated and characterized.

A cross-sectional survey of Aedes aegypti immature abundance in urban and rural household containers in central Colombia

BackgroundAedes aegypti, the major vector of dengue, breeds in domestic water containers. The development of immature mosquitoes in such containers is influenced by various environmental, ecological and socioeconomic factors. Urban and rural disparities in water storage practices and water source supply may affect mosquito immature abundance and, potentially, dengue risk. We evaluated the effect of water and container characteristics on A. aegypti immature abundance in urban and rural areas. Data were collected in the wet season of 2011 in central Colombia from 36 urban and 35 rural containers, which were either mosquito-positive or negative. Immature mosquitoes were identified to species. Data on water and container characteristics were collected from all containers.ResultsA total of 1452 Aedes pupae and larvae were collected of which 81% were A. aegypti and 19% A. fluviatilis. Aedes aegypti immatures were found in both urban and rural sites. However, the mean number of A. aegypti pupae was five times higher in containers in the urban sites compared to those in the rural sites. One of the important factors associated with A. aegypti infestation was frequency of container washing. Monthly-washed or never-washed containers were both about four times more likely to be infested than those washed every week. There were no significant differences between urban and rural sites in frequency of washing containers. Aedes aegypti immature infestation was positively associated with total dissolved solids, but negatively associated with dissolved oxygen. Water temperature, total dissolved solids, ammonia, nitrate, and organic matter were significantly higher in urban than in rural containers, which might explain urban-rural differences in breeding of A. aegypti. However, many of these factors vary substantially between studies and in their degree of association with vector breeding, therefore they may not be reliable indices for vector control interventions.ConclusionsAlthough containers in urban areas were more likely to be infested with A. aegypti, rural containers still provide suitable habitats for A. aegypti. Containers that are washed more frequent are less likely to produce A. aegypti. These results highlight the importance of container washing as an effective vector control tool in both urban and rural areas. In addition, alternative designs of the highly productive washbasins should continue to be explored. To control diseases such as dengue, Zika and chikungunya, effective vector breeding site control must be implemented in addition to other interventions.

Effect of niloticin, a protolimonoid isolated from Limonia acidissima L. (Rutaceae) on the immature stages of dengue vector Aedes aegypti L. (Diptera: Culicidae)

The aim of the present study was to evaluate the mosquitocidal activity of fractions and a compound niloticin from the hexane extract of Limonia acidissima L. leaves on eggs, larvae and pupae of Aedes aegypti L. (Diptera: Culicidae). In these bioassays, the eggs, larvae and pupae were exposed to concentrations of 2.5, 5.0, 7.5 and 10.0ppm for fractions and 0.5, 1.0, 1.5 and 2.0ppm for compound. After 24h, the mortality was assessed and the LC50 and LC90 values were calculated for larvae and pupae. Per cent ovicidal activity was calculated for eggs after 120h post treatment. Among the sixteen fractions screened, fraction 8 from the hexane extract of L. acidissima generated good mosquitocidal activity against Ae. aegypti. The LC50 and LC90 values of fraction 8 were 4.11, 8.04ppm against Ae. aegypti larvae and 4.19, 8.10ppm against Ae. aegypti pupae, respectively. Further, the isolated compound, niloticin recorded strong larvicidal and pupicidal activities. The 2ppm concentration of niloticin showed 100% larvicidal and pupicidal activities in 24h. The LC50 and LC90 values of niloticin on Ae. aegypti larvae were 0.44, 1.17ppm and on pupae were 0.62, 1.45ppm, respectively. Niloticin presented 83.2% ovicidal activity at 2ppm concentration after 120h post treatment and niloticin exhibited significant growth disruption and morphological deformities at sub lethal concentrations against Ae. aegypti. The structure of the isolated compound was identified on the basis of single XRD and spectral data (1H NMR and 13C NMR) and compared with literature spectral data. The results indicate that niloticin could be used as a potential natural mosquitocide.

Higher mosquito production in low-income neighborhoods of Baltimore and Washington, DC: understanding ecological drivers and mosquito-borne disease risk in temperate cities.

Mosquito-vectored pathogens are responsible for devastating human diseases and are (re)emerging in many urban environments. Effective mosquito control in urban landscapes relies on improved understanding of the complex interactions between the ecological and social factors that define where mosquito populations can grow. We compared the density of mosquito habitat and pupae production across economically varying neighborhoods in two temperate U.S. cities (Baltimore, MD and Washington, DC). Seven species of mosquito larvae were recorded. The invasive Aedes albopictus was the only species found in all neighborhoods. Culex pipiens, a primary vector of West Nile virus (WNV), was most abundant in Baltimore, which also had more tire habitats. Both Culex and Aedes pupae were more likely to be sampled in neighborhoods categorized as being below median income level in each city and Aedes pupae density was also greater in container habitats found in these lower income neighborhoods. We infer that lower income residents may experience greater exposure to potential disease vectors and Baltimore residents specifically, were at greater risk of exposure to the predominant WNV vector. However, we also found that resident-reported mosquito nuisance was not correlated with our measured risk index, indicating a potentially important mismatch between motivation needed to engage participation in control efforts and the relative importance of control among neighborhoods.

Efficacy of Various Larvicides against &lt;i&gt;Aedes aegypti&lt;/i&gt; Immatures in the Laboratory

We conducted a laboratory study to evaluate the efficacy of control agents against small larvae, large larvae, and pupae of Aedes aegypti to determine an appropriate larvicide regime to employ in emergency dengue control programs. The control agents included Bacillus thuringiensis var. israelensis (Bti), pyriproxyfen (an insect growth regulator), a larvicidal oil, Aquatain AMF (polydimethylsiloxane, a monomolecular film), and temephos at the recommend application dosages and rates. Our results showed that Bti, pyriproxyfen, and temephos were efficacious (100% mortality) against larvae, irrespective of the instar stage, but not against pupae of Ae. aegypti (1.5-7.8% mortality). Aquatain AMF, on the other hand, was very effective at controlling the pupal stage (100% mortality), but had limited efficacy against small larvae (38.0% mortality) and large larvae (78.0% mortality). The larvicidal oil was effective against all immature stages (93.3-100% mortality). Therefore, we concluded that for effectively interrupting the dengue transmission cycle, larvicides that kill the pupal stage (Aquatain AMF or larvicidal oil) should be included in an emergency dengue control program in addition to Bti, pyriproxyfen, or temephos.

Estimating dengue vector abundance in the wet and dry season: implications for targeted vector control in urban and peri-urban Asia

Background: Research has shown that the classical Stegomyia indices (or “larval indices”) of the dengue vector Aedes aegypti reflect the absence or presence of the vector but do not provide accurate measures of adult mosquito density. In contrast, pupal indices as collected in pupal productivity surveys are a much better proxy indicator for adult vector abundance. However, it is unknown when it is most optimal to conduct pupal productivity surveys, in the wet or in the dry season or in both, to inform control services about the most productive water container types and if this pattern varies among different ecological settings.Methods: A multi-country study in randomly selected twelve to twenty urban and peri-urban neighborhoods (“clusters”) of six Asian countries, in which all water holding containers were examined for larvae and pupae of Aedes aegypti during the dry season and the wet season and their productivity was characterized by water container types. In addition, meteorological data and information on reported dengue cases were collected.Findings: The study reconfirmed the association between rainfall and dengue cases (“dengue season”) and underlined the importance of determining through pupal productivity surveys the “most productive containers types”, responsible for the majority (>70%) of adult dengue vectors. The variety of productive container types was greater during the wet than during the dry season, but included practically all container types productive in the dry season. Container types producing pupae were usually different from those infested by larvae indicating that containers with larval infestations do not necessarily foster pupal development and thus the production of adult Aedes mosquitoes.Conclusion: Pupal productivity surveys conducted during the wet season will identify almost all of the most productive container types for both the dry and wet seasons and will therefore facilitate cost-effective targeted interventions.

Eco-bio-social research on dengue in Asia: a multicountry study on ecosystem and community-based approaches for the control of dengue vectors in urban and peri-urban Asia

This article provides an overview of methods and cross-site insights of a 5-year research and capacity building initiative conducted between 2006 and 2011 in six countries of South Asia (India, Sri Lanka) and South-East Asia (Indonesia, Myanmar, Philippines, Thailand).The initiative managed an interdisciplinary investigation of ecological, biological, and social (i.e., eco-bio-social) dimensions of dengue in urban and peri-urban areas, and developed community-based interventions aimed at reducing dengue vector breeding and viral transmission. The multicountry study comprised interdisciplinary research groups from six leading Asian research institutions. The groups conducted a detailed situation analysis to identify and characterize local eco-bio-social conditions, and formed a community-of-practice for EcoHealth research where group partners disseminated results and collaboratively developed site-specific intervention tools for vector-borne diseases. In sites where water containers produced more than 70% of Aedes pupae, interventions ranged from mechanical lid covers for containers to biological control. Where small discarded containers presented the main problem, groups experimented with solid waste management, composting and recycling schemes. Many intervention tools were locally produced and all tools were implemented through community partnership strategies. All sites developed socially and culturally appropriate health education materials. The study also mobilised and empowered women’s, students’ and community groups and at several sites organized new volunteer groups for environmental health. The initiative’s programmes showed significant impact on vector densities in some sites. Other sites showed varying effect — partially attributable to the ‘contamination’ of control groups — yet led to significant outcomes at the community level where local groups united around broad interests in environmental hygiene and sanitation. The programme’s findings are relevant for defining efficient, effective and ecologically sound vector control interventions based on local evidence and in accordance with WHO’s strategy for integrated vector management.

Community-based control of Aedes aegypti by adoption of eco-health methods in Chennai City, India

Background: Dengue is highly endemic in Chennai city, South India, in spite of continuous vector control efforts. This intervention study was aimed at establishing the efficacy as well as the favouring and limiting factors relating to a community-based environmental intervention package to control the dengue vector Aedes aegypti.Methods: A cluster randomized controlled trial was designed to measure the outcome of a new vector control package and process analysis; different data collection tools were used to determine the performance. Ten randomly selected intervention clusters (neighbourhoods with 100 houses each) were paired with ten control clusters on the basis of ecological/entomological indices and sociological parameters collected during baseline studies. In the intervention clusters, Aedes control was carried out using a community-based environmental management approach like provision of water container covers through community actors, clean-up campaigns, and dissemination of dengue information through schoolchildren. The main outcome measure was reduction in pupal indices (pupae per person index), used as a proxy measure of adult vectors, in the intervention clusters compared to the control clusters.Results: At baseline, almost half the respondents did not know that dengue is serious but preventable, or that it is transmitted by mosquitoes. The stakeholder analysis showed that dengue vector control is carried out by vertically structured programmes of national, state, and local administrative bodies through fogging and larval control with temephos, without any involvement of community-based organizations, and that vector control efforts were conducted in an isolated and irregular way. The most productive container types for Aedes pupae were cement tanks, drums, and discarded containers. All ten intervention clusters with a total of 1000 houses and 4639 inhabitants received the intervention while the ten control clusters with a total of 1000 houses and 4439 inhabitants received only the routine government services and some of the information education and communication project materials. The follow-up studies showed that there was a substantial increase in dengue understanding in the intervention group with only minor knowledge changes in the control group. Community involvement and the partnership among stakeholders (particularly women’s self-help groups) worked well. After 10 months of intervention, the pupae per person index was significantly reduced to 0·004 pupae per person from 1·075 (P = 0·020) in the intervention clusters compared to control clusters. There were also significant reductions in the Stegomyia indices: the house index was reduced to 4·2%, the container index to 1·05%, and the Breteau index to 4·3 from the baseline values of 19·6, 8·91, and 30·8 in the intervention arm.Conclusion: A community-based approach together with other stakeholders that promoted interventions to prevent dengue vector breeding led to a substantial reduction in dengue vector density.

Dengue vector management using insecticide treated materials and targeted interventions on productive breeding-sites in Guatemala

BackgroundIn view of the epidemiological expansion of dengue worldwide and the availability of new tools and strategies particularly for controlling the primary dengue vector Aedes aegypti, an intervention study was set up to test the efficacy, cost and feasibility of a combined approach of insecticide treated materials (ITMs) alone and in combination with appropriate targeted interventions of the most productive vector breeding-sites.MethodsThe study was conducted as a cluster randomized community trial using “reduction of the vector population” as the main outcome variable. The trial had two arms: 10 intervention clusters (neighborhoods) and 10 control clusters in the town of Poptun Guatemala. Activities included entomological assessments (characteristics of breeding-sites, pupal productivity, Stegomyia indices) at baseline, 6 weeks after the first intervention (coverage of window and exterior doorways made of PermaNet 2.0 netting, factory treated with deltamethrin at 55 mg/m2, and of 200 L drums with similar treated material) and 6 weeks after the second intervention (combination of treated materials and other suitable interventions targeting productive breeding-sites i.e larviciding with Temephos, elimination etc.). The second intervention took place 17 months after the first intervention. The insecticide residual activity and the insecticidal content were also studied at different intervals. Additionally, information about demographic characteristics, cost of the intervention, coverage of houses protected and satisfaction in the population with the interventions was collected.ResultsAt baseline (during the dry season) a variety of productive container types for Aedes pupae were identified: various container types holding >20 L, 200 L drums, washbasins and buckets (producing 83.7% of all pupae). After covering 100% of windows and exterior doorways and a small number of drums (where the commercial cover could be fixed) in 970 study households, tropical rains occurred in the area and lead to an increase of the vector population, more pronounced (but statistically not significant) in the control arm than in the intervention arm. In the second intervention (17 months later and six weeks after implementing the second intervention) the combined approach of ITMs and a combination of appropriate interventions against productive containers (Temephos in >200 L water drums, elimination of small discarded tins and bottles) lead to significant differences on reductions of the total number of pupae (P = 0.04) and the House index (P = 0.01) between intervention and control clusters, and to borderline differences on reductions of the Pupae per Person and Breteau indices (P = 0.05). The insecticide residual activity on treated curtains was high until month 18 but the chemical concentration showed a high variability. The cost per house protected with treated curtains and drum covers and targeting productive breeding-sites of the dengue vector was $ 5.31 USD. The acceptance of the measure was generally high, particularly in families who had experienced dengue.ConclusionEven under difficult environmental conditions (open houses, tropical rainfall, challenging container types mainly in the peridomestic environment) the combination of insecticide treated curtains and to a less extent drum covers and interventions targeting the productive container types can reduce the dengue vector population significantly.

AN ALTERNATIVE SPATIAL ANALYSIS OF BREEDING SITES DISTRIBUTION TO SUPPORT CONTROL ACTIVITIES FOR DENGUE.

Background/aim Dengue is an urban re-emerging infectious disease. In Cali-Colombia the disease is endemic and during the last years it has shown and increasing trend to larger outbreaks and more severe dengue cases. Control programs carry out actions to reduce populations of Aedes aegypti mosquitoes by detecting areas with high indexes of infestation (i.e.; more than 5% of recipients with Aedes pupae or larvae) and, subsequently, eliminating positive breeding sites. However, evaluations have not been developed about the role of negative, but potential, breeding sites in the dynamic of transmission. The objective of this study was to evaluate the distribution of positive and potential breeding sites inside households and in peri-domiciliar spaces. Methods A geographic information systems(GIS) was implemented at a high space scale for storing, processing and analyzing data by using geo-statistical techniques(Kriging). We determined the spatial relationship between positive and potential breeding sites distributions. Results Only 56%(R-squared) of the spatial variability of positive breeding sites distribution was associated to variability of potential breeding sites. 15,2% of the study area comprises zones with a simultaneous presence of high potential-high positive breeding sites and 64,2% of the area presented low potential-low positive breeding sites. However, 20,6% of the area presented a differential distribution of these types of breeding sites (5,1% high potential-low positive and 15,5% low potential-high positive). Maps were built to identify areas showing this lack of agreement in the distribution. Conclusion Our results suggest that focusing interventions in areas only presenting high infestation with positive breeding sites might fail because they do not take into account the variability in breeding sites from potential to positive. Elimination and education activities could be better implemented taking into account the distribution of potential breeding sites.

Spinosad as an effective larvicide for control of Aedes albopictus and Aedes aegypti, vectors of dengue in southern Mexico

Field trials were conducted during the wet and dry seasons in periurban and semi-rural cemeteries in southern Mexico to determine the efficacy of a suspension concentrate formulation of spinosad (Tracer 480SC) on the inhibition of development of Aedes albopictus L. and Ae. aegypti Skuse. For this, oviposition traps were treated with spinosad (1 or 5 mg L(-1)), Bacillus thuringiensis israelensis (Bti, VectoBac 12AS), a sustained release formulation of temephos and a water control. Ae. albopictus was subordinate to Ae. aegypti during the dry season, but became dominant or codominant during the wet season at both sites. The two species could not be differentiated in field counts on oviposition traps. Mean numbers of larvae + pupae of Aedes spp. in Bti-treated containers were similar to the control at both sites during both seasons. The duration of complete absence of aquatic stages varied from 5 to 13 weeks for the spinosad treatments and from 6 to 9 weeks for the temephos treatment, depending on site, season and product concentration. Predatory Toxorhynchites theobaldi Dyar and Knab suffered low mortality in control and Bti treatments, but high mortality in spinosad and temephos treatments. Egg counts and percentage of egg hatch of Aedes spp. increased significantly between the dry and wet seasons, but significant treatment differences were not detected. Temephos granules and a suspension concentrate formulation of spinosad were both highly effective larvicides against Ae. aegypti and Ae. albopictus. These compounds merit detailed evaluation for inclusion in integrated control programs targeted at Ae. aegypti and Ae. albopictus in regions where they represent important vectors of human diseases.

Defective Rainwater Harvesting Structure and Dengue Vector Productivity Compared with Peridomestic Habitats in a Coastal Town in Southern India

Productivity of defective rainwater harvesting structures (RWHS) and other peridomestic habitats for dengue vector was assessed in a coastal town in Tamil Nadu, southern India, where dengue cases were reported. Of 31,709 houses, 792, 790, and 759 were surveyed during southwest monsoon, northeast monsoon, and summer season, and RWHS were found in 651, 638, and 544 houses, respectively. Of these RWHS, 23.3, 34.6 and 14.2% had defects; 20.7, 30.9, and 11.8% were holding water; and 6.5, 11.9, and 5.7% supported dengue vectors. Six types of RWHS, namely, open percolation pit, covered percolation pit, sealed percolation pit, rechargeable trench with bore, and structures connected to well in use or disuse were found. Number of female pupae of Aedes, i.e., pupal productivity obtained from RWHS ranged from 114 in summer to 1,174 in northeast monsoon, and open percolation pit contributed maximum (11.5%). The productivity of habitats other than RWHS varied from 635 in summer to 1,754 in northeast monsoon. Overall, the pupal productivity recorded from RWHS was 30.1% and in other habitats was 69.9%. A hierarchical cluster analysis showed three clusters of 23 types of habitats, which differed significantly in pupal production (F = 426.4, P < 0.05). Cluster I consists of 15 habitats, namely, disused well, RWHS-disused well, RWHS-used well, metal container, coconut shell, glass bottle, sealed percolation pit, used well, ornamental container, tree stump, defrost water collection tray, disposable cup, flower pot, broken toilet ware, and sun shade. Cluster II includes seven habitats, i.e., grinding stone, open percolation pit, covered percolation pit, cement tank, mud pot, plastic container, and rechargeable trench with bore, and cluster III includes automobile tire alone. Cluster II and III contributed to 80.1% of the total pupal production, whereas the remaining 19.9% by cluster I. The study showed that the defective RWHS, particularly open and covered percolation pits were found to be among the key containers, propagating Aedes population. The pupae per person obtained during northeast monsoon in different houses varied between 0.077 and 2.839 (average 0.864). House and Breteau Indices were relatively higher during northeast monsoon, whereas the Container Index was higher in southwest monsoon. In view of risk of dengue vectors propagation, the need for source reduction involving community and prioritizing control measures toward the highly productive water-holdings is discussed.

Defective Rainwater Harvesting Structure and Dengue Vector Productivity Compared with Peridomestic Habitats in a Coastal Town in Southern India

Productivity of defective rainwater harvesting structures (RWHS) and other peridomestic habitats for dengue vector was assessed in a coastal town in Tamil Nadu, southern India, where dengue cases were reported. Of 31,709 houses, 792, 790, and 759 were surveyed during southwest monsoon, northeast monsoon, and summer season, and RWHS were found in 651, 638, and 544 houses, respectively. Of these RWHS, 23.3, 34.6 and 14.2% had defects; 20.7, 30.9, and 11.8% were holding water; and 6.5, 11.9, and 5.7% supported dengue vectors. Six types of RWHS, namely, open percolation pit, covered percolation pit, sealed percolation pit, rechargeable trench with bore, and structures connected to well in use or disuse were found. Number of female pupae of Aedes, i.e., pupal productivity obtained from RWHS ranged from 114 in summer to 1,174 in northeast monsoon, and open percolation pit contributed maximum (11.5%). The productivity of habitats other than RWHS varied from 635 in summer to 1,754 in northeast monsoon. Overall, the pupal productivity recorded from RWHS was 30.1% and in other habitats was 69.9%. A hierarchical cluster analysis showed three clusters of 23 types of habitats, which differed significantly in pupal production (F = 426.4, P < 0.05). Cluster I consists of 15 habitats, namely, disused well, RWHS-disused well, RWHS-used well, metal container, coconut shell, glass bottle, sealed percolation pit, used well, ornamental container, tree stump, defrost water collection tray, disposable cup, flower pot, broken toilet ware, and sun shade. Cluster II includes seven habitats, i.e., grinding stone, open percolation pit, covered percolation pit, cement tank, mud pot, plastic container, and rechargeable trench with bore, and cluster III includes automobile tire alone. Cluster II and III contributed to 80.1% of the total pupal production, whereas the remaining 19.9% by cluster I. The study showed that the defective RWHS, particularly open and covered percolation pits were found to be among the key containers, propagating Aedes population. The pupae per person obtained during northeast monsoon in different houses varied between 0.077 and 2.839 (average 0.864). House and Breteau Indices were relatively higher during northeast monsoon, whereas the Container Index was higher in southwest monsoon. In view of risk of dengue vectors propagation, the need for source reduction involving community and prioritizing control measures toward the highly productive water-holdings is discussed.