The objective of this study was to assess the effectiveness of BG-Sentinel (BGS) traps for mass trapping at the household level to control the dengue vector, Aedes aegypti (L.), in Manaus (Brazil) by performing a cluster randomized controlled trial. After an initial questionnaire and baseline monitoring, 6 out of 12 clusters were randomly allocated to the intervention arm, where participating premises received one BGS trap for mass trapping. The other six clusters did not receive traps and were considered as the control arm. Biweekly monitoring with BGS in both arms assessed the impact of mass trapping. At the end of the study, a serological survey was conducted and a second questionnaire was conducted in the intervention arm. Entomological monitoring indicated that mass trapping with BGS traps significantly reduced the abundance of adult female Ae. aegypti during the first five rainy months. In the subsequent dry season when the mosquito population was lower, no effect of mass trapping was observed. Fewer Ae. aegypti females were measured in the intervention arm during the next rainy period, but no significant difference between arms was observed. The serological survey revealed that in participating houses of mass trapping areas recent dengue infections were less common than in control areas, although this effect was not statistically significant. The majority of participants responded positively to questions concerning user satisfaction. Our results suggest that BGS traps are a promising tool which might be deployed as part of dengue control programs; however, further investigations and larger scale studies are necessary.
Ovitraps baited with grass infusions were evaluated in the field as oviposition attractants or stimulants for Aedes (Stegomyia) mosquitoes. Significantly higher oviposition by Aedes aegypti (L.) was observed in areas with no vegetation, but intense human presence, whereas Aedes albopictus (Skuse) oviposition was significantly higher in areas with vegetation, regardless of human presence. Ovitraps baited with infusions of Panicum maximum (Jacq.) collected significantly more eggs than controls containing tap water. Moreover, the number of eggs deposited in ovitraps baited with infusion made from fresh, mature leaves was higher compared with dried leaves or fresh, immature leaves. Anaerobically fermented of grass infusions were more attractive than either aerobically fermented or sterilized infusions of P. maximum. The fermentation age of the grass infusion also affected the oviposition response of mosquitoes. Significantly more eggs were deposited in baited ovitraps containing a fresh leaf infusion of P. maximum fermented for 15 or 20 d, compared with the controls. This demonstrates that 15- or 20-d anaerobic fermentation made of fresh, fully mature leaves of P. maximum is the optimum infusion for ovitrap-based Aedes (Stegomyia) surveillance mosquitoes in Brazil. Neglecting to consider these differences in infusion attractiveness may introduce significant variation in surveillance results.
The objective of this study was to evaluate the effectiveness of Aedes aegypti mass trapping using the sticky trap MosquiTRAP (MQT) by performing a cluster randomised controlled trial in Manaus, state of Amazonas, Brazil. After an initial questionnaire and baseline monitoring of adult Ae. aegypti abundance with BG-Sentinel (BGS) traps in six clusters, three clusters were randomly assigned to the intervention arm where each participating household received three MQTs for mass trapping during 17 months. The remaining three clusters (control arm) did not receive traps. The effect of mass trapping on adult Ae. aegypti abundance was monitored fortnightly with BGS traps. During the last two months of the study, a serological survey was conducted. After the study, a second questionnaire was applied in the intervention arm. Entomological monitoring indicated that MQT mass trapping did not reduce adult Ae. aegypti abundance. The serological survey indicated that recent dengue infections were equally frequent in the intervention and the control arm. Most participants responded positively to questions concerning user satisfaction. According to the results, there is no evidence that mass trapping with MQTs can be used as a part of dengue control programs. The use of this sticky trap is only recommendable for dengue vector monitoring.
BackgroundTransovarial transmission of dengue virus in Aedes spp. mosquitoes is considered an important mechanism for the maintenance of the virus in nature and may be implicated in the occurrence of outbreaks and epidemics of the disease. However, there are few studies involving transovarial transmission and viral vector monitoring as a surveillance tool and control strategy. The present study evaluated transovarial transmission of dengue virus in Aedes aegypti populations as a xenomonitoring strategy in municipalities of the Amazonas state.Results Aedes sp. eggs (13.164) were collected, with 30% viability of third- and fourth-instar larvae. Transovarial transmission of DENV was detected in all municipalities. The transovarial infection rate (TOR) in the municipalities was 46% of the DENV positive samples. The minimum infection rate (MIR) was 17.7 in the state, varying from 11.4 to 24.1 per 1,000 larvae tested in the respective municipalities. Four DENV serotypes were identified, with DENV I and IV being present in all municipalities investigated. The number of reported dengue fever cases varied during this period.ConclusionsOur results suggest that transovarial transmission may be an important mechanism for the maintenance and spreading of the disease in Amazonas municipalities. Using qRT-PCR, it was possible to identify the four DENV serotypes in larval samples. The methodology used in the present study proved suitable as a DENV xenomonitoring model in immature mosquitoes, contributing to the development of systems for early detection of viral circulation and predictive models for the occurrence of outbreaks and epidemics of this disease.Trial registration CAAE34025414200005015.
This study relates multiple parameters that are involved in the occurrence and control of malaria in the Amazon. Ebbs and floods, black and white waters, fishponds, and ''repiquete'' (Amazonian waters phenomenon) influence the density of Anopheles darlingi Root, 1926. The adaptive processes, genetic background, and resilience of Anopheles vectors change in response to climate and environmental changes. This study covers the diversity of anophelines, which increases due to anthropic activities. Regarding strategies for vector control, the following measures are important: (1) use mechanical barriers inside houses (screens and impregnated mosquito nets), (2) determine the level of anopheline resistance to insecticides, and (3) determine the effect of the physiological state of females on malaria transmission effectiveness. Bioinsecticides were found to be efficient in the control of immatures, and there was no alteration of the associated fauna. Data on genetic variability and vector populations demonstrated greater polymorphism in intradomicile subpopulations. Furthermore, knowledge on the structural genome and transcriptome of A. darlingi, associated with bio-ecology and evolution, may indicate an adaptive strategy of this species to the Amazon biome. There are anthropic activities and environmental and climatic changes that favor increased vector density, requiring specific control strategies to reduce populations of this species.
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