DWFP Toxicology Research to Develop Insecticides for Vector Control

Julia W. Pridgeon, PhDToxicologist/Molecular Biologist

02-14-07

Mosquito and Fly Research UnitCenter for Medical, Agricultural, and

Veterinary EntomologyUSDA-ARS, 1600 SW 23rd Drive

Gainesville, FL 32608

Research Objective

To discover and develop effective

chemical and molecular

insecticides for vector control

Military Relevance

♣ In military units, arthropod-borne diseases continue to be serious threats to deployed troops

♣ Chemical pesticides are the most effective way to control disease vectors, however, few products are available for military use

♣ Due to the nature of military operations, pesticides that can quickly and effectively eliminate arthropod vectors are highly desirable

Approach for the Development of Effective Chemical Insecticides

Registered Pesticides

Natural PlantChemicals

Plant ExtractsDesigner

Chemicals

USDA-ARS-NPURU

USDA-ARS-MFRU

NPURU & UF IRAC

High-Throughput Screen to find highly toxic chemical(Topical application; Aedes aegypti model)

Small Chamber Test and Field Evaluation

Topical Application

EasyAccurate

Small Amount Fast

Results of Studies on Chemical Insecticides

Registered Pesticides

Natural PlantChemicals

Plant Extracts

33

DesignerChemicals

USDA-ARS-NPURU

USDA-ARS-MFRU NPURU & UF IRAC

Pesticide LD50 (ug)

Fipronil 1.3 10-6

Permethrin 1.4 10-4

Spinosad 2.5 10-3

Bifenzate 4.25

19 26

AT-05-27-2(LD50 0.3ug)

123-1(LD50 = 0.4ug)

Bacopa monnieri (Water hyssop)Methanol Extract

LD50 125ug

33

LD50 =0.8ug

LD50 =2.1ug

LD50 =14.72ug

Summary on Studies of Chemical Insecticides

1)Screened 19 registered pesticides; several showed high insecticidal activity against Aedes aegypti

2)Screened 26 different natural plant chemicals (NPURU); two had relatively high toxicities

3) Screened 33 different plant extracts (MFRU), some had higher toxicity against mosquitoes than others

4) Screened 33 piperidines with different structures (UF and NPURU), 2-ethyl piperidines showed the highest toxicities against mosquito (in press in Journal of Medical Entomology)

Summary on Studies of Chemical Insecticides

Future Studies on Chemical Pesticides

1)Evaluate the toxicities of registered pesticides against different species of mosquitoes and other disease vectors

2)Select the best pesticide candidates for further evaluation in small chamber tests and field studies

3)Manipulate the structures of plant chemicals and evaluate their toxicities

4) Studies on toxicity of plant extracts will be continued (additional information by Dr. Quinn)

5) For structure-activity analysis, different classes of chemicals will be evaluated and the best ones chosen for further structure manipulation

Future Studies on Chemical Pesticides

Approach for the Developmentof Molecular Pesticides

(Aedes aegypti model)

Target Essential Target Essential PathwaysPathways Programmed Cell Death,

Mitochondria Pathway, etc

Molecular Cloning(DNA, RNA, PCR)

Vector, Carrier, Formulation

(Aedes aegypti model)

Bioassays

Molecular Pesticide Construction

Control Molecular Pesticide 1

Molecular Pesticide 2 Molecular Pesticide 3

Cell Assay

Evaluation of Molecular Pesticides

Adult Assay

Evaluation of Molecular Pesticides

Control Molecular Pesticides

1)Cell and adult assays have demonstrated that critical pathways can be targeted to develop molecular pesticides

2)Using Aedes aegypti as a model organism, molecular pesticides are effective and fast-killing (within 6 hours)

SummaryDevelopment of Molecular Pesticides

1)Identify new critical pathways to target

2)Produce additional molecular pesticides and evaluate their efficacy

3)Select best molecular pesticides and evaluate production and application methods (formulation, carriers, etc)

Future StudiesDevelopment of Molecular Pesticides

Overall Summary

1)Screened known registered pesticides; several showed high insecticidal activity

2)Screened different natural plant chemicals (NPURU), two had relatively high toxicities against mosquitoes

Overall Summary (Cont’d)

3) Screened 33 piperidines (UF & NPURU) with different structures, 2-ethyl piperidine showed the highest toxicity (in press in JME)

4) Cell and adult assays have demonstrated that critical pathways can be targeted to develop molecular pesticides (patent pending)

5) Using Aedes aegypti as a model organism, molecular pesticides are effective and fast-killing (within 6 hours)

AcknowledgmentsDr. James J. BecnelDr. Gary G. ClarkDr. Sandra AllanDr. Dan KlineDr. Ulrich Bernier

Dr. Brian QuinnDr. Chris GedenDr. Roberto PereiraDr. Jerry HogsetteDr. Ken Linthicum

Dr. Liming ZhaoHeather FurlongGreg AllenNathan NewlonJoyce Urban

Mosquito and Fly Research Unit, USDA-ARS-CMAVE

Dr. Kumudini Meepagala

Natural Products Utilization Research Unit, USDA-ARS

Dr. Alan Katritzky Department of Chemistry, University of Florida

Dr. Daniel Strickman

National Program Leader, Program 104, USDA-ARS

Dr. Graham WhiteDepartment of Entomology, University of Florida

Deployed War-Fighter Protection Research Program