Project : USDA ARS

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Research Project: Biting Arthropod Surveillance and Control

Location: Mosquito and Fly Research

2019 Annual Report

Objectives
1. Discover safe toxicants and behavior-altering chemicals. 1.A. Discover and develop new attractants for mosquitoes and other biting arthropods. 1.B. Discover and develop new topical repellents for mosquitoes and other biting arthropods. 1.C. Discover and develop new toxicants for mosquitoes and other biting arthropods. 1.D. Discover and develop dsRNA molecules for control of mosquitoes and other biting arthropods. 2. Develop and evaluate systems that disrupt arthropod dispersal, biting, host-finding, or survival. 2.A. Evaluate new fabric treatments and optimize existing treatments to provide improved protection from insect bites through military and civilian clothing. 2.B. Evaluate and optimize spatial repellent systems that protect hosts from arthropods in a local area. 2.C. Evaluate new and optimize existing treated targets. 2.D. Evaluate approaches to disinsection of aircraft. 2.E. Evaluate factors that influence the efficacy of aerosol application and residual pesticide barrier applications on natural and artificial materials in various ecological habitats, including assessment of efficacy in future climates based upon climate projection models. Design the best application methods to mitigate changing climate. 3. Improve accuracy and utility of surveillance techniques. 3.A. Evaluate new and optimize existing trapping systems. 3.B. Develop methods and techniques to accurately assess and predict mosquito population density and timing, and to deploy mosquito vector surveillance systems. Discover and characterize environmental predictors influenced by climate change that measure the risk of disease from pathogens transmitted by mosquitoes.

Approach
A research focus of this plan is the discovery and development of new chemicals that impact arthropods. The discovery of new repellents will allow improved personal protection from topical application to skin (Sub-objective 1.A), or in a local area through release of chemical in dispersion systems (Sub-objective 2.B). The discovery of new toxicants (Sub-objective 1.C) has potential utility in treated clothing (Sub-objective 2.A) and treated targets (Sub-objective 2.C). New dsRNA molecules that function as insecticides (Sub-objective 1.D) provide a safe and novel means of insect control. Research on how environmental factors influence aerosol and residual control strategies will provide a means for more efficient arthropod control (Sub-objective 2.E). Novel attractants (Sub-objective 1.A) will allow more accurate and efficient surveillance when utilized in new and optimized trapping systems (Sub-objective 3.A). Improved surveillance trapping systems (Sub-objective 3.A) and increased accuracy in prediction of local arthropod populations based on surveillance trap studies (Sub-objective 3.B) will improve models for disease risk and enhance the effectiveness of control strategies. A better understanding of the relationship between environmental factors, and in particular climate change, will allow accurate prediction of vector-borne disease risk in a geographic area and thereby, when and where to employ control strategies to reduce debilitating and lethal illnesses in humans and other animals (Objective 4).

Progress Report
This is the final report for project 6036-32000-050-00D.We leveraged a diversity of environments across four field sites (hot arid southern California, warm temperate north Florida, hot humid Thailand, and warm-Mediterranean Greece long-term research sites) to investigate capabilities of novel transfluthrin spatial repellent formulations targeting mosquitoes, sand flies, and biting Tabanid flies. We continued to develop with university and mosquito control district collaborators an unprecedented system to reduce human-biting disease vector populations of Aedes aegypti mosquitoes in an Atlantic Coast Florida city by preparing and mass releasing sterilized colony-reared male Aedes aegypti. We conducted the first known parallel trials of a suite of biological-based and a suite of synthetic liquid and granular larvicides targeting disease vector Aedes and Anopheles species, applied with eight different thermal fog, cold mist, ULV, and forced air sprayers across four ecologically diverse field sites to determine optimal combinations of formulation and application technique. We conducted a large scale aerial adulticide experiment in a simulated urban village targeting Aedes aegypti in a warm temperate north Florida environment using a dye additive to track droplets producing for the first time with this spray system a map of efficacy (sentinel mosquito mortality) and pesticide droplet distribution. With NASA and other US government agency partners we produced the first description and demonstration of global disease burden increases related to recent El Niño climate activity and associated climate anomalies, including analytical techniques that could be used to geographically predict specific disease risk in future El Niño scenarios. We continued to successfully forecast and issue updates to WHO, FAO, and OIE for elevated risk of Rift Valley fever outbreaks in endemic regions using global climate data with NASA and DoD partners.

Accomplishments
1. Variation in larvicide efficacy against disease vector Aedes and Anopheles mosquitoes. The Aedes aegypti mosquito is a key vector of prominent viruses including dengue, chikungunya, Zika, yellow fever, Mayaro, and Madariaga and is very difficult to control. Similarly, a large suite of Anopheles species mosquitoes can transmit malaria parasites among humans and both Aedes aegypti and Anopheles species display increasing resistance to pesticides targeting their adult stages, potentially favoring operational control programs that include larval control. However, mosquito control programs are universally limited and may not be present to apply larvicides when Aedes or Anopheles habitats become flooded. ARS scientists at Gainesville, Florida, and US and international collaborators conducted the first known parallel trials of an array of synthetic and biologically-based liquid larvicides applied as a residual with 7 different sprayers in key hot-arid, warm-temperate/subtropical, Mediterranean, and wet-and dry-season tropical natural and urban structure habitats. Results indicated that pre-treatment of habitats with residual larvicides could be effective against these species on a gradient determined by relative exposure through vegetation or distance into the urban structure, application equipment, weathering time, target species, and application environment. Importantly, pre-treatment of dry habitat vulnerable to flooding can be used in response to mosquito forecasting models produced by ARS scientists at Gainesville, Florida, and can significantly extend the impact of mosquito control agencies that otherwise must treat flooded areas cyclically or in response to mosquito populations that are already developing.

2. Spatial repellents are effective across a range of environments against mosquitoes, sand flies, and biting flies. Standard control methodologies such as aerosol pesticide sprays or residual pesticides applied to natural and artificial materials may be effective at reducing incursion of medically important mosquito, sand fly, and filth fly biting and nuisance insects into protected perimeters. However, heavy mortality from these techniques contributes to the pervasive burden of resistance in these key target insects. ARS scientists at Gainesville, Florida, and US and international collaborators designed groundbreaking studies in 4 ecologically distinct and militarily relevant environments to investigate the capability of a spatial repellent, transfluthrin, to reduce vector and biting/nuisance insect incursion into protected perimeters without inducing mortality. Transfluthrin was applied to strips of 4 types of US military material and exposed to natural populations of disease vector sand flies and mosquitoes, and nuisance biting populations of tabanids across the 4 environments. Target insects were significantly reduced in protected perimeters, and a unique bioassay developed with university collaborators showed that the presence of transfluthrin could repel without target insect death. Importantly, strips are easily transported and attached to existing perimeters or structures by minimally trained personnel, creating a rapid shelter from biting insects without having to wait for intervention by mosquito and vector control units. Data, analysis, and interpretation from these unique investigations provided key material (https://www.regulations.gov/document?D=EPA-HQ-OPP-2016-0581-0013) for US Environmental Protection Agency registration (https://www3.epa.gov/pesticides/chem_search/ppls/000432-01588-20180928.pdf) of this important new integrated vector management tool.

U.S. DEPARTMENT OF AGRICULTURE

Mosquito and Fly Research: Gainesville, FL