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United States Department of Agriculture

Agricultural Research Service


Location: Mosquito and Fly Research Unit

2011 Annual Report

1a.Objectives (from AD-416)
1. Determine components of behavior leading to resource location by Aedes albopictus and Culex pipiens group species/hybrids. Resources to be studied are: resting sites, sugar sources, mates, blood-meal hosts, and oviposition sites. 2. Determine chemical and other cues associated with regulation and orientation of specific behaviors by Aedes albopictus, Culex pipiens group species/hybrids, and Ixodes scapularis that can be applied to the solution of operational surveillance and control problems.

3. Discover and characterize environmental predictors of the distribution of mosquitoes in order to assess the risk of invasive species and pathogen transmission. Apply to the development of methods and techniques to accurately assess mosquito population density, to deploy vector surveillance systems, and to detect exotic invasive species. Discover the current, and estimate the future (with changing climate) of spatial and temporal distribution of the mosquito vectors of vector-borne diseases in the United States.

1b.Approach (from AD-416)
1. Conduct laboratory studies to describe and characterize behavioral steps involved in resource finding by mosquitoes that may facilitate discovery of new approaches for surveillance and control. 2. Determine factors that result in positive resting site selection responses by adult mosquitoes as a basis for optimizing use of natural and artificial shelters for surveillance of mosquitoes. Determine volatile chemical cues associated with mate location through behavioral and chemical studies. Determine cues used for location and utilization of sugar and nectar sources. Using behavioral, chemical and electrophysiological methods, plant-derived compounds that attract mosquitoes will be identified and then evaluated in the field for surveillance. Determine factors that influence host-finding behavior with emphasis on the discovery of new chemical attractants based on host odors. Visual, thermal, and other non-chemical cues enhance host-finding behavioral responses to olfactory cues and these will be evaluated to enhance trap efficiency. Devise strategies for mosquito surveillance that utilize cues from oviposition sites. Using behavioral and chemical analysis, new chemical attractants will be identified and evaluated in the field. Determine cues that regulate behaviors in ticks with specific focus on the role of host odor compounds that may provide attractants for surveillance. Evaluate the effect of toxicant exposure on arthropod behavior through detailed behavioral analysis to better target toxicant impact.

3. Develop methods and techniques to accurately assess mosquito population density through comparison of trapping, resting, and landing collections. Characterize environmental predictors of mosquito distribution in time and space through field sampling and spatio-temporal models to provide strategies for accurate assessment of mosquito populations. Discover and develop ecologic and climatic factors to assess population densities of actual and potential vector mosquitoes in the US, and using Rift Valley fever (RVF) as a model disease system, evaluate the risk of exotic species and disease introduction into the U.S. 4. Identify and evaluate attractants for larval mosquitoes that can be developed and tested in the field to provide new strategies for larval surveillance.

3.Progress Report
The ultimate goal of this research was to discover, evaluate and incorporate aspects of the sensory ecology of blood-seeking arthropods into useful tools and deployment strategies for surveillance and control. Rift Valley fever (RVF) virus is an emerging mosquito-borne pathogen with the potential for severe impact on veterinary and public heath in the U.S. ARS scientists with interagency collaboration predicted a 2010 RVF outbreak in South Africa based on extensive climatic and vegetative factors. This research contributes to national and international efforts by researchers to predict and conduct preventative measures for future RVF outbreaks. A better understanding of the biology and behavior of mosquitoes can drive refinement and optimization of traps and their placement which, in turn, enhances disease and population surveillance. New attractants can enhance efficacy of traps. New volatile mosquito-produced mating attractants for Aedes aegypti were discovered through chemical identification and laboratory olfactometer studies. Several flowering plants highly attractive to both male and female Asian Tiger mosquitoes have also been discovered and these will provide the foundation for determination of new chemical attractants. Efficacy of traps for collection of different target species of biting flies differs with trap color, orientation and the blend of attractants. These factors have been optimized for different targets, thereby enhancing surveillance capabilities. Resting boxes are an essential tool for sampling Culex mosquitoes and factors that enhance collection of mosquitoes from these boxes have been developed. Results from larval mosquito sampling are used to guide mosquito control decisions, yet traps are not used for this life stage. Lights of different colors evaluated in the laboratory attracted larvae of different species of mosquitoes and can provide the basis for development of a standardized larval surveillance method. Correct placement of traps is essential for enhanced collection of mosquitoes. The discovery of enhanced oviposition by the Asian Tiger mosquito in the presence of a species of flowering plant should lead to the development of more efficient surveillance and control strategies for this mosquito species. Environmental predictors of mosquito distribution were used to optimize placement of traps to enhance mosquito collection. Use of one type of traps may not accurately assess actual mosquito populations and trapping studies conducted provide the basis for correction factors between trapping methods.

1. Predicted Rift Valley fever activity in Africa. Built upon 2006-2010 foundation of strategic inter-agency partnerships and synthesis of research programs to protect the U.S. against Rift Valley fever (RVF). Rift Valley fever virus (RVFV) is a potential emerging mosquito-borne viral threat that could lead to severe impacts on the economy and public and veterinary health should it emerge in the U.S. Mosquito and Fly Research Unit (MFRU) scientists were part of a team that predicted the ongoing RVF outbreak in South Africa, leading to early detection. Predicted an outbreak of RVF for the years 2008-2011 for Southern Africa. The outbreak in 2011 was more widespread than in the previous outbreaks of 2008, 2009 and 2010 including the Cape region of South Africa and parts of Namibia. MFRU staff continued to maintain the organization of key researchers and administrators from federal and state agencies and universities into the RFV Working Group (RVFWG). The RVFWG continues to have a measurable positive impact on RVF research directions and outcomes and sets a trajectory that will significantly strengthen and protect the U.S. against the possible arrival of RVFV, as well as other mosquito-borne viruses currently or potentially impacting the U.S. economy and public and veterinary health. MFRU staff participated in international RVF meetings in the U.S. and Nairobi, Kenya, and published a landmark article in the American Journal of Tropical Medicine and Hygiene on the successful prediction of the 2006-2008 RVF outbreaks in Africa.

2. Identification of flowering plants attractive to host seeking Asian Tiger mosquitoes. Identification of plant odors that alert mosquitoes to the location of sugar and nectar meals, required for adult mosquito activities such as flight. In laboratory bioassay studies, ARS researchers at Gainesville, FL, identified two plants whose intact flowers and solvent washes of these flowers were very attractive to both male and female mosquitoes. This discovery should result in the development of novel surveillance and control strategies.

3. Identification of mosquito-produced mating attractants for Aedes aegypti. Surveillance of adult Aedes aegypti is limited by the lack of effective and specific attractants for use in traps. In olfactometer studies at the Mosquito and Fly Research Unit (MFRU), evidence of volatile mosquito-produced attractants for this species was discovered. Subsequent extracts and chemical analyses revealed several compounds that affect behavior of males and females. These chemicals will provide the basis for optimization of a lure that could be used in surveillance for this species in national and international public health and nuisance insect programs.

4. Optimization has been achieved for several target species. Trap color, orientation and odor blend affects host-finding behavior of mosquitoes and other biting flies. ARS researchers at Gainesville, FL, have found that “one size does not fit all,” when it comes to trapping mosquitoes and other biting flies. Aedes aegypti and Ae. albopictus showed a definite preference for trap color. Whereas Ae. aegypti oriented to blue traps, Ae. albopictus demonstrated a definite preference for black and red traps. The currently used best commercial trap for these two species is white, which in our studies caught the fewest adult females. Not all species respond to the same combination of visual, physical and chemical cues. Species composition and relative abundance will change with trap shape, orientation, color and whether host odors are present or not. This knowledge may enhance development of effective traps which will be useful in the early detection and monitoring of invasive species.

5. Determine factors influencing in resting site selection by Culex. A complex of natural and artificial structures in a north Florida swamp was inspected for resting adult mosquitoes. Mosquitoes collected comprised six species in four genera with the composition and density of collections highly variable within and between resting structure types. Additional methods-development is underway in the study venue to standardize conventional battery/gas-powered mechanical aspiration equipment for use as a sampling tool for resting adult mosquito populations. In screened cage studies using 5 cm cubic "red boxes," resting mosquito populations manifested cyclical entry and exit responses that correlated respectively with increasing light intensity and resting surface temperature. Other predictors of entry/exit activity were moisture content of the resting site substrate and compass orientation of the box opening. This knowledge will result in new and improved detection and trapping systems for exotic, invasive, and indigenous mosquito species that transmit disease agents to domestic livestock, humans, and wildlife.

6. Laboratory evaluation of lights for attraction of mosquito larvae. Sampling for mosquito larvae is primarily based on dipping which is confounded by larval response to disturbance. Development of an effective passive surveillance method would greatly enhance accuracy of population estimates and ultimately enhance mosquito control efforts. Laboratory evaluation at the Mosquito and Fly Research Unit of light-emitting diodes (LEDs) of different wavelengths revealed differences in optimal wavelengths for Aedes aegypti, Culex quinquefasciatus and Anopheles quadrimaculatus larvae. LEDs that are most effective will be incorporated in a field comparison of sampling methods. Specific LED lights optimal to the attraction of mosquito larvae have been discovered and can provide the basis for development of an objective larval surveillance tool. This would enhance accurate forecasting of increased populations of pest and vector mosquitoes and guide pathogen surveillance and mosquito control efforts.

7. Flowering plants focus oviposition activity of Asian Tiger mosquitoes. Asian Tiger mosquitoes deposit few eggs in many containers and, as such, it is difficult to treat and control all of the containers that have eggs in them. ARS researchers in Gainesville, FL, have discovered that females will deposit the majority of their eggs into a single container that has a particular species of this flowering plant. This discovery should lead to the development of more efficient control strategies and can be utilized by mosquito abatement programs.

8. Characterize environmental predictors of mosquito distribution. Three study sites identified in a north Florida swamp comprise one 15 ha plot of irregular shape and two linear (500 m) transects. Global Positioning System (GPS) coordinates combined with aerial imagery and cartographic data have been used to depict the physical and biological features of each site. Additional methods development is underway to support the selection of trap location(s) within each plot/transect and will entail the evaluation of mosquito responses to the effects of trap placement, adjacent traps, microclimate, and CO2 source location. This knowledge will result in new and improved detection and trapping systems for exotic, invasive, and indigenous mosquito species that transmit disease agents to domestic livestock, humans, and wildlife.

9. Develop methods to assess mosquito population density. The number of female mosquitoes captured by suction traps and in portable light traps baited with CO2 in a north Florida swamp was compared with the number of mosquitoes captured when landing on a human subject. Among all three sampling methods, 19 species in 8 genera were collected although not all mosquito species were captured in light traps or in suction traps. For species that were collected by each trap type and when landing on a human subject apparent density depended in each case on the sampling method. Under-estimation of mosquito density in light trap samples, relative to the density of landing mosquitoes, ranged (depending on the species) from 43-97% and over-estimation from 80-85%. Corresponding values for suction trap samples were 28-88% and 17-87%. This knowledge will result in new systems for the deployment of adult mosquito traps in detection and surveillance systems for exotic, invasive, and indigenous mosquito species that transmit disease agents to domestic livestock, humans, and wildlife.

Review Publications
Kline, D.L., Hogsette, Jr, J.A., Muller, G.C. 2011. Evaluation of propane combustion traps for collection of Phlebotomus papatasi (Scopoli) in southern Israel. Journal of Vector Ecology. 36(1):S166-S171.

Zhao, L., Becnel, J.J., Clark, G.G., Linthicum, K., Chen, J., Jin, X. 2010. Identification and expression profile of multiple genes in response to magnesium exposure in Culex quinquefasciatus larvae. Journal of Medical Entomology. 47(6):1053-1061.

Zhao, L., Chen, J., Becnel, J.J., Kline, D.L., Clark, G.G., Linthicum, K. 2011. Identification and transcription profiling of Trypsin in Aedes taeniorhynchus (Diptera: Culicidae): Developmental regulation, blood feeding, and Permethrin exposure. Journal of Medical Entomology. 48(3):546-553.

Tabachnick, W.J., Harvey, W.R., Becnel, J.J., Clark, G.G., Connelly, C.R., Day, J.F., Linser, P.J., Linthicum, K. 2011. Countering a Bioterrorist Introduction of Pathogen-Infected Mosquitoes through Mosquito Control. Journal of the American Mosquito Control Association. 27(2):165-167.

Xue, R., Barnard, D.R. 2010. Effects of body size and nutritional regimen on survival in adult Aedes albopictus (Diptera: Culicidae). Journal of Medical Entomology. 47(5):778-782. DOI: 10/1603/ME09222.

Kamalalkannan, S., Murugan, K., Barnard, D.R. 2011. Toxicity of Acalypha indica (Euphorbiaceae) and Achyranthes aspera (Amaranthaceae) leaf extracts to Aedes aegypti (Diptera: Culicidae). Journal of Asia-Pacific Entomology. 14:41-45.

Allan, S.A. 2011. Susceptibility of mosquitoes to insecticides in a liquid sucrose bait. Journal of Vector Ecology. 36(1):59-67.

Kline, D.L., Hogsette, Jr, J.A., Muller, G.C. 2011. Comparison of various configurations of CDC-type traps for the collection of Phlebotomus papatasi (Scopoli) in southern Israel. Journal of Vector Ecology. 36(1):S212-S218.

Allan, S.A. 2010. Chemical ecology of tick-host interactions. In: Takken, W., Knols, B. J.G., editors. Ecology and Control of Vector-borne Disease Volume 2. Olfaction in Vector-host Interactions. Wageningen, Netherlands:Wageningen Academic Press. p. 327-348.

Vrzal, E.M., Allan, S.A., Hahn, D.A. 2010. Amino acids in nectar enhance longevity of female Culex quinquefasciatus mosquitoes. Journal of Insect Physiology. 56(11):1659-1664.

Linthicum, K., Anyamba, A., Chretien, J., Small, J., Tucker, C.J., Britch, S.C. 2010. The Role of Global Climate Patterns in the Spatial and Temporal Distribution of Vector-Borne Disease. In: Atkinson, P.W., editor. Vector Biology, Ecology and Control. New York, NY: Springer. p. 3-13.

Linthicum, K. 2010. Controlling vector-borne disease and adapting to climate change with novel research on disease forecasting to target new vector control materials and technologies. In: M. Zaim, editor. Report of the Seventh Meeting of the Global Collaboration for Development of Pesticides for Public Health, World Health Organization, Geneva, Switzerland. p. 50-53.

Obenauer, P.J., Kaufman, P.E., Kline, D.L., Allan, S.A. 2010. Detection of and Monitoring for Aedes albopictus (Diptera: Culicidae) in Suburban and Sylvatic Habitats in North Central Florida using Four Sampling Techniques. Environmental Entomology. 39(5):1608-1616.

Linthicum, K. 2010. The Example of Eastern Africa: the dynamic of Rift Valley fever and tools for monitoring virus activity. In de La Rocque, S., Formenty, P. editors. Rift Valley fever Outbreaks Forecasting Models. Rome, Italy. p. 8-9.

Stafford Iii, K.C., Allan, S.A. 2010. Field Applications of Entomopathogenic Fungi Beauveria bassiana (Hypocreales: Clavicipitaceae) and Metarhizium anisopliae F52 (Hypocreales: Nectriaceae) for the Control of Ixodes scapularis (Acari: Ixodidae). Journal of Medical Entomology. 47(6):1107-1115.

Cooperband, M.F., Golden, F.V., Clark, G.G., Jany, W., Allan, S.A. 2010. Prallethrin-induced excitation increases contact between sprayed ultra-low-volume droplets and flying mosquitoes (Diptera: Culicidae) in a wind tunnel. Journal of Medical Entomology. 47(6):1099-1106.

Obenauer, P.J., Allan, S.A., Kaufman, P.E. 2010. Aedes albopictus (Diptera: Culicidae) Oviposition Response to Organic Infusions from Common Flora of Suburban Florida. Journal of the American Mosquito Control Association. 25(4):517-520.

Mccann, S., Day, J.F., Allan, S.A., Lord, C.C. 2009. Age modifies effect of body size on fecundity in Culex quinquefasciatus Say (Diptera: Culicidae). Journal of Vector Ecology. 34(2):174-181.

Clark, G.G., Bernier, U.R., Allan, S.A., Kline, D.L., Golden, F.V. 2011. Changes in host-seeking behavior of Puerto Rican Aedes aegypti (L.) following colonization. Journal of Medical Entomology. 48(4):533-537. DOI: 10.1603/ME10207

Xue, R., Qualls, W.A., Kline, D.L., Zhao, T. 2010. Evaluation of lurex 3tm, octenol, and CO2 Sachet as baits in mosquito magnet pro traps against floodwater mosquitoes. Journal of the American Mosquito Control Association. 26(3):344-345.

Junnila, A., Kline, D.L., Mueller, G.C. 2011. Comparative efficacy of small commercial traps for the capture of adult Phlebotomus papatasi. Journal of Vector Ecology. 36(1):172-178.

Allan, S.A., Bernier, U.R., Kline, D.L. 2010. Laboratory evaluation of human-associated odors on attraction of Culex spp. (Diptera:Culicidae). Journal of Vector Ecology. 35:318-324.

Barnard, D.R., Knue, G.J., Dickerson, C.Z., Bernier, U.R., Kline, D.L. 2011. Relationship between mosquito (Diptera: Culicidae) landing rates on a human subject and numbers captured using CO2-baited light traps. Bulletin of Entomological Research. 101:277-285.

Last Modified: 4/20/2014
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