Location: Mosquito and Fly Research2015 Annual Report
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.
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).
Initiated multi-year observational studies on the phenology of flowering plants at selected sites to determine which plants were in seasonal synchrony with target biting fly species population abundance. Identified at least one flowering plant that is used by anophelines for nectar feeding. A total of 88 compounds were tested as mosquito repellents. About 40 percent of these were highly repellent to mosquitoes. Conducted genomic and functional studies on mosquito pathogens. Genomic and deep sequencing investigations and analysis on the genomes of two species of microsporidia (Edhazardia aedis and Vavraia culicis) and the mosquito immune response to infection was conducted. The new information obtained here contributes to our basic understanding on the organization of the genomes of these parasites. The bite protection of US Marine Corps (USMC) Enhanced Fire-Resistant Combat Ensemble (EFRCE) were evaluated and found to provide excellent protection from mosquito bites. Etofenprox was explored as a new clothing treatment and found to perform superior at preventing mosquitoes from biting through the fabric, out to 75 wash cycles of the uniform fabrics. A completely passive device was developed to release chemicals for attracting and repelling mosquitoes and other biting flies. Testing of prototype air curtain units was completed and a report was sent to WHO asking for their recommendation of the air curtain system for use in commercial aircraft. A groundbreaking study was conducted; this study demonstrated efficacy of residual pesticides on two key US military field materials, HESCO blast wall geotextile and ULCANS radar-scattering camouflage netting, in a hot humid tropical environment in Thailand to reduce populations of medically important mosquitoes. A completely passive device was developed to release chemicals for attracting and repelling mosquitoes and other biting flies. Statistical algorithms were developed to adjust mosquito numbers in mechanical traps to the mosquito landing rate on a human subject. Data were used to develop a statistical model that explains environmental effects on mosquito responses to mechanical traps. Developed and conducted novel analyses to relate long-term dynamics of medically-important mosquito populations, including potential vectors of Rift Valley fever (RVF), in Georgia and Kansas to long-term weather and climate dynamics. These analyses led to the identification of seasonal signals in the environment that presage unusually large populations of important mosquito vectors, which could provide weeks to months of warning to target mosquito surveillance, disease surveillance, and mosquito control.
1. Next Generation Military Uniform Repellent. The Mosquito and Fly Research Unit collected data for a Good Laboratory Practice (GLP) study involving the evaluation of etofenprox-treated uniforms for the U.S. military. The study took place in the summer of 2015 and was completed by July 31. The data will be reported to the U.S. Environmental Protection Agency (EPA) in an October meeting and registration of this product for treatment of uniforms is expected in July, 2016. This product will likely be used in commercial garments and will eventually replace permethrin as the safer alternative. The protocol used for this study will be written into a guideline by U.S. EPA for the future registration of repellent-treated clothing.
2. Improved barrier treatment for the military. Conducted groundbreaking study demonstrating efficacy of residual pesticides on two key US military field materials, HESCO blast wall geotextile and ULCANS radar-scattering camouflage netting, in a hot humid tropical environment in Thailand to reduce populations of medically important mosquitoes including day-biting Aedes (dengue and chikungunya vector) mosquitoes and night-biting Anopheles (malaria vector) mosquitoes. Residual pesticide-treated materials were then synergistically enhanced with a misting system calibrated to dispense pesticide space spray synchronized with peak population activity of day- and night-biting mosquitoes, which further reduced biting populations as well as supplementing the long-term residual treatment on the material from deposition of mist. Conducted groundbreaking study of aerially applied pesticides against mosquitoes in a hot-arid desert environment in Southern California, demonstrating that a formulation of synergized prallethrin, sumithrin, and PBO can be effective in temperatures exceeding 100%F and <5% relative humidity. This study also provided additional evidence that existing models of spray deposition used to guide aerial applications of pesticide in the US do not adequately represent actual spray deposition, and may be improved to reduce pesticide use and better track the fate of sprayed pesticide droplets. These findings will be integrated into future versions of the Mobile Pesticide App (http://www.ars.usda.gov/Business/docs.htm?docid=24908).
3. Conducted genomic and functional studies on mosquito pathogens. Microbial pathogens have developed strategies to successfully infect, evade or debilitate host defense systems and kill mosquitoes. Microsporidian parasites are known to infect many mosquitoes worldwide, but fundamental knowledge on the genomes of mosquito microsporidia and host-pathogen interactions are poorly known. Genomic and deep sequencing investigations and analysis on the genomes of two species of microsporidia (Edhazardia aedis and Vavraia culicis) and the mosquito immune response to infection was conducted. Genomic analysis and deep RNA-Seq across infection time courses reveal fundamental differences between these pathogens. E. aedis retains enhanced cell surface modification and signaling capacity, upregulating protein trafficking and secretion dynamically during infection. V. culicis is less dependent on its host for basic metabolites and retains a subset of spliceosomal components, with a transcriptome broadly focused on growth and replication. Transcriptional profiling of mosquito immune responses reveals that response to infection by E. aedis differs dramatically depending on the mode of infection, and that antimicrobial defensins may play a general role in mosquito defense against Microsporidia. This analysis illuminates fundamentally different evolutionary paths and host interplay of specialist and generalist pathogens. The new information obtained here contributes to our basic understanding on the organization of the genomes of these parasites and will be incorporated into the Eukaryotic Pathogen Database Resource EupathDB (http://eupathdb.org/eupathdb/) and specifically the Microsporidia Genome Resource MicrosporidiaDB (http://microsporidiadb.org/micro/). Plans are also in place to incorporate the mosquito responses of Aedes aegypti and Anopheles quadrimaculatus to challenge by microsporidia into VectorBase, the Bioinformatics Resource for Invertebrate Vectors of Human Pathogen.
4. Improved military uniform treatment process. The Walter Reed Army Institute of Research (WRAIR) requested that we examine a plasma application process for impregnation of permethrin repellent in U.S. Army Fire-Resistant Army Combat Uniforms (FRACUs) and 50/50 nylon cotton Army Combat Uniforms (ACU). We discovered that even though the application process treated the garments at about 33% the initial allowed application rate (US EPA regulation), there was superior protection and permethrin retention after 20 and 50 washings. The FRACU bite protection of volunteers was in the 90-100% range through 20 wash cycles, and above 80% protection at 50 wash cycles. The ACU was nearly 100% protective against mosquito bites through 50 wash cycles. These results are very promising for an improved factory treatment process that the US military and civilians can use to protect themselves from ticks and from mosquito bites through clothing.
5. Developed and conducted novel analyses to relate long-term dynamics of medically-important mosquito populations, including potential vectors of Rift Valley fever (RVF), in Georgia and Kansas to long-term weather and climate dynamics. These analyses led to the identification of seasonal signals in the environment that presage unusually large populations of important mosquito vectors, which could provide weeks to months of warning to target mosquito surveillance, disease surveillance, and mosquito control. The ongoing products of such population-environment analyses will be coordinated with monitoring of RVF activity in endemic African regions conducted by the joint USDA-ARS-CMAVE and NASA-GSFC effort, and funded in part by the DoD Armed Forces Health Surveillance Center (http://www.ars.usda.gov/Business/Docs.htm?docid=23464), to enhance awareness in US public health agencies and vector control districts of risk of arrival of RVF in the US.
6. Discovery of novel insecticides. Approximately 52 novel compounds based on the fipronil backbone structure. One third of these resulted in 80% mortality of adult Aedes aegypti at 100 µmol. Several of the complexes of these compounds were more toxic than fipronil and an invention disclosure will be filed to cover the discovery of these compound.
7. New devices for the release of spatial repellents. A completely passive device was developed to release chemicals for attracting and repelling mosquitoes and other biting flies. The device releases an active ingredient agnostically. Until activated, the device can be stored or handled without exposing people or livestock to the active ingredient. The device can be used by public health professionals for the development of both novel surveillance and population management strategies.
8. Improved trap deployment strategies for surveillance. Statistical algorithms were developed to adjust mosquito numbers in mechanical traps to the mosquito landing rate on a human subject. Data were used to develop a statistical model that explains environmental effects on mosquito responses to mechanical traps. The impact of this research is that these sampling algorithms and the statistical model enable quantitative understanding of mosquito responses to mechanical traps and are a critical first step in the development of science-based trap deployment strategies for mosquito vector detection and surveillance systems.
9. Potential new mosquito repellent actives and products. In the past year, a total of 88 compounds from 6 different collaborating groups were examined. Many of these were follow-up studies from lead compounds already identified with the collaborators. A total of 53 of these 88 demonstrated some repellency at the 1.5 mg/cm2 level, and 33 of these were repellent at concentrations of less than 0.100 mg/cm2. For comparative purposes, DEET repels typically at surface concentrations of 0.050-0.090 mg/ cm2. Dose-Response studies were conducted to evaluate adjuvants to improve the efficacy of DEET. The data generated indicate there are two binary compositions that are superior to DEET alone. This study may be repeated under GLP conditions, to generate data in support of US EPA registration of a new repellent product.
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