Using body size as an indicator for age structure in field populations of Aedes aegypti (Diptera: Culicidae)

Abstract

Background The Aedesaegypti mosquito is a vector of several viruses including dengue, chikungunya, zika, and yellow fever. Vector surveillance and control are the primary methods used for the control and prevention of disease transmission; however, public health institutions largely rely on measures of population abundance as a trigger for initiating control activities. Previous research found evidence that at the northern edge of Ae.aegypti’s geographic range, survival, rather than abundance, is likely to be the factor limiting disease transmission. In this study, we sought to test the utility of using body size as an entomological index to surveil changes in the age structure of field-collected female Aedesaegypti. Methods We collected female Ae.aegypti mosquitoes using BG sentinel traps in three cities at the northern edge of their geographic range. Collections took place during their active season over the course of 3 years. Female wing size was measured as an estimate of body size, and reproductive status was characterized by examining ovary tracheation. Chronological age was determined by measuring transcript abundance of an age-dependent gene. These data were then tested with female abundance at each site and weather data from the estimated larval development period and adulthood (1 week prior to capture). Two sources of weather data were tested to determine which was more appropriate for evaluating impacts on mosquito physiology. All variables were then used to parameterize structural equation models to predict age. Results In comparing city-specific NOAA weather data and site-specific data from HOBO remote temperature and humidity loggers, we found that HOBO data were more tightly associated with body size. This information is useful for justifying the cost of more precise weather monitoring when studying intra-population heterogeneity of eco-physiological factors. We found that body size itself was not significantly associated with age. Of all the variables measured, we found that best fitting model for age included temperature during development, body size, female abundance, and relative humidity in the 1 week prior to capture . The strength of models improved drastically when testing one city at a time, with Hermosillo (the only study city with seasonal dengue transmission) having the best fitting model for age. Despite our finding that there was a bias in the body size of mosquitoes collected alive from the BG sentinel traps that favored large females, there was still sufficient variation in the size of females collected alive to show that inclusion of this entomological indicator improved the predictive capacity of our models. Conclusions Inclusion of body size data increased the strength of weather-based models for age. Importantly, we found that variation in age was greater within cities than between cities, suggesting that modeling of age must be made on a city-by-city basis. These results contribute to efforts to use weather forecasts to predict changes in the probability of disease transmission by mosquito vectors. Graphical abstract

How much do you need to survive? Minimal nutritional levels to complete the development on Aedes aegypti (Diptera: Culicidae)

“…Dead adults were collected daily, organized in Eppendorf tubes by treatment/replicate and stored at -18 °C. Sexing and measurement of the left wing (ventral view) was performed for each dead adult individual as a measure of allometry (Gutiérrez et al, 2022). These measurements were made using a Zeiss Stemi 305 binocular stereoscopic microscope at 40× magnification.…”

Influence of insular conditions on wing phenotypic variation in two dominant mosquito vectors, Aedes albopictus and Armigeres subalbatus (Diptera: Culicidae), in the border archipelagos of Thailand

“…Understanding the population dynamics of mosquito species is essential to facilitate the development of more efficient vector control strategies, ultimately contributing to the successful control of mosquito‐borne diseases (Benelli et al, 2016; World Health Organization, 2013). Investigation of physiological variation in mosquitoes offers crucial insights into their responses to environmental and geographical factors in targeted areas (Garzón & Schweigmann, 2018; Gutiérrez et al, 2022). Wing geometric morphometrics (GM) is a quantitative examination of wing characteristics, including size and shape, through statistical analysis based on Cartesian landmark coordinates (Dujardin, 2011; Lorenz et al, 2017; Wilke et al, 2016).…”