This qualitative study aimed to describe field worker perceptions, evaluations of worth, and time costs of routine dengue vector surveillance methods in Cairns (Australia), Kuala Lumpur and Petaling District (Malaysia). In Cairns, the BG-Sentinel trap is a favored method for field workers because of its user-friendliness, but is not as cost-efficient as the sticky ovitrap. In Kuala Lumpur, the Mosquito Larvae Trapping Device is perceived as a solution for the inaccessibility of premises to larval surveys. Nonetheless, the larval survey method is retained in Malaysia for prompt detection of dengue vectors. For dengue vector surveillance to be successful, there needs to be not only technical, quantitative evaluations of method performance but also an appreciation of how amenable field workers are to using particular methods. Here, we report novel field worker perceptions of dengue vector surveillance methods in addition to time analysis for each method.
We investigated spatial autocorrelation of female Aedes aegypti L. mosquito abundance from BG-Sentinel trap and sticky ovitrap collections in Cairns, north Queensland, Australia. BG-Sentinel trap collections in 2010 show a significant spatial autocorrelation across the study site and over a smaller spatial extent, while sticky ovitrap collections only indicate a non-significant, weak spatial autocorrelation. The BG-Sentinel trap collections were suitable for spatial interpolation using ordinary kriging and cokriging techniques. The uses of Premise Condition Index and potential breeding container data have helped improve our prediction of vector abundance. Semiovariograms and prediction maps indicate that the spatial autocorrelation of mosquito abundance determined by BG-Sentinel traps extends farther compared to sticky ovitrap collections. Based on our data, fewer BG-Sentinel traps are required to represent vector abundance at a series of houses compared to sticky ovitraps. A lack of spatial structure was observed following vector control treatment in the area. This finding has implications for the design and costs of dengue vector surveillance programs.
In some laboratories, mosquitoes' direct blood-feeding on live animals has been replaced with various membrane blood-feeding systems. The selection of blood meal sources used in membrane feeding is crucial in vector mass rearing as it influences the mosquitoes' development and reproductive fitness. Therefore, this scoping review aimed to evaluate the existing literature on the use of different blood sources and components in artificial membrane feeding systems and their effects on blood-feeding and the fecundity rate of Ae. aegypti. A literature review search was conducted by using PubMed, Scopus, and Web of Science databases according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA-ScR). The EndNote version 20 software was used to import all searched articles. Relevant information was retrieved for analysis into a Microsoft Excel Spreadsheet. A total of 104 full-text articles were assessed for eligibility criteria, whereby the articles should include the comparison between different types of blood source by using the membrane feeding systems. Only 16 articles were finally included in the analysis. Several studies had reported that human blood was superior in blood-feeding Ae. aegypti as compared to sheep blood which resulted in lower fecundity due to accumulation of free fatty acids (FFA) in the cuticles. In contrast, cattle whole blood and pig whole blood showed no significant differences in the blood-feeding and fecundity rate as compared to human blood. This review also indicated that bovine whole blood and pig whole blood enhanced Ae. aegypti's vitellogenesis and egg production as compared to plasma and blood cells. In addition, human blood of up to 10 days after the expiration date could still be used to establish Ae. aegypti colonies with good blood-feeding rates and number of eggs produced. Thus, future studies must consider the importance of selecting suitable blood sources and components for membrane blood feeding especially in mosquito colonisation and control measure studies.
Permanent mounting of fourth instar mosquito larvae is essential for identifying Aedes spp. This procedure requires extensive exposure to xylene, a clearing agent in the mounting process. We investigated wintergreen oil as a substitute for xylene. Five hundred larvae were mounted on slides to evaluate shrinkage or expansion of specimens after clearing using xylene or wintergreen oil. We examined the ventral brush and siphonal hair tufts for species identification and for preservation of morphological characteristics after clearing specimens in xylene or wintergreen oil. Shrinkage of the length of whole larvae and width of the head, thorax and abdomen after mounting was significantly greater after clearing with xylene than with wintergreen oil. The length of the comb scale nearest the ventral brush was similar for both clearing agents. The clarity of the specimens after mounting was improved by clearing with wintergreen oil, but the integrity of the ventral brush and siphonal hair tufts were similar for both clearing agents.