Andre Costa-da-Silva, Ph.D.
Unprecedented expansion of Aedes aegypti population throughout the world have been occurring in the last 5 years, causing serious arboviruses outbreaks and pathogen introduction in new areas, as recently reported for Zika virus in Miami-Dade County. In this scenario, mosquito surveillance and population suppression strategies are fundamental methods to better design Ae. aegypti control programs and effectively combat this unique vector. Ae. aegypti gravid females need to find suitable artificial breeding sites in anthropomorphic/urbanized environments to lay their eggs after a successful blood meal on a vertebrate host. Oviposition behavior is one of the most important and sensible moments in mosquito life cycle. Taking advantage of this process and finding new ways to interfere with oviposition site-seeking behavior (OSSB) is an opportunity to develop efficient trapping methods. Consequently, the screening of more potent attractant volatiles that can lure gravid females to gravid traps are fundamental to improve intervention activities based upon population suppression strategies. The primary objectives of this project are: to identify and evaluate more efficient egg-laying Ae. aegypti female’s attractant volatiles to generate an Ae. aegypti field-trapped sample library and colonies to study population genetics, genomics and olfactory behavior of this vector in South Florida.
We are screening potential volatile compounds in the laboratory using 2-choice oviposition assays in cages and other behavior experiments. Moreover, we have validated an assay to compare laying preferences in the field by applying paired in-home-developed Highly Attractive Biological Insecticide Trap (HABITrap) scented with the candidate compounds. We have deployed odor-scented traps with Geosmin (trans-1,10-dimethyl-trans-9-decalol), a molecule potentially attractive to Ae. aegypti gravid females in the field. We were able to demonstrate Geosmin shifts the oviposition preference inside the traps, validating previous findings from laboratory assays. We were also able to test honey volatiles in the same fashion since the previous literature and our laboratory assays supported flower odors as potential attractants for egg-laying females. Although we were able to characterize this oviposition preference towards honey-scented breeding sites in laboratory assays, the same results were not confirmed in the field. Recently, we have developed a specific Y-olfactometer for studying egg-laying females, named “Oviseekmeter”. We are finishing the validation of this device, which will improve our capacity to screen more candidate attractants and blends to lure egg-laying Ae. aegypti females. The future direction includes testing hay infusion mixed with Geosmin, both in different concentrations to generate a potent blend to bait the HABItraps and other gravid traps.
We have collected Ae. aegypti eggs across 20 sites in Miami-Dade County and surrounding regions aiming to establish field-trapped sample library together with laboratory colonies originated from G0 adults from South Florida. A total of 14,725 eggs were collected during HABItrap trials over 20 sites in a one-year period. We found high level of Ae. aegypti infestation with only one site negative for eggs, and rare occurrence of Ae. albopictus eggs (only 1 site). Moreover, we coordinated a 2018 summer internship program at Florida International University, enabling us to expand our collections for additional 30 sites. The next goals are to produce a diverse mosquito sample library and robust colonies established from field mosquitoes to allow us to explore population genetics, genomic diversity, new insecticide markers, and variability in olfactory-related genes and behavior in Ae. aegyptimosquitoes from South Florida.
The broad objectives of this project are to improve Ae. aegypti population supression methods by enhancing biological insecticide traps targeting egg-laying females and generate an Ae. aegypti genomic-widemapping of genetic diversity and population structure across Florida to discover the basis of vector adaption, specific behaviors and insecticide resistance. The project outcomes will translate in improved scientific-driven surveillanceand control strattegies focusing the suppression of vector population in South Florida.