High throughput testing for toxic and behavior modifying chemicals against Phlebotomine sand flies.

1
High throughput testing for toxic and behavior
modifying chemicals against Phlebotomine sand
flies.

• Edgar D. Rowton, John P. Grieco, Russell E.
  Coleman
• WRAIR, Silver Spring, MD USUHS, Bethesda,
  MD

DoD Tri-Service Pest Mgmt Workshop, 13 Feb 2007
2
Background

• Leishmaniasis in Old World is vectored by sand
  flies (Diptera Phlebotominae, Phlebotomus spp.)

Photo courtesy Ed Rowton
Photo courtesy LTC Russ Coleman

• Iraq PPMs, residual spraying not effective.

Photo courtesy COL Peter Weina
3
Objective

• Screen compounds for toxicity, contact irritancy
  (excito-repellency) and/or spatial repellency
  against sand flies.
• Existing compounds with known effect vs.
  mosquitoes
• DDT
• Permethrin
• a-cypermethrin
• Novel compounds
• SS220
• DH220
• DH5
• Cmpd1
• Cmpd2
• Acetone (control)

SS220 derivatives
USDA proprietary plant derivatives
4
Methods

• Design assay chamber
• Prepare test compounds
• Conduct assays
• Toxicity assay
• Contact irritancy (exito-repellency) assay
• Spatial repellency assay

5
Modified assay chamber

• Grieco High Throughput modular assay chamber
  for mosquitoes.

Chamber re-designed for sand flies to eliminate
hiding places and secure test screen.
Grieco et al., J Am Mosq Control Assoc. 2005,
Vol. 21.
6
Prepare test screens
Insert with treated screen
25 nM/cm2 test compound applied to nylon organdy
material.
Place insert into metal chamber for assay.
7
Assay 1 Toxicity
X ?
Treated screen

• Sand flies exposed for 1 hour.

• Mortality determined at 1 24 hours.

8
Toxicity Assay
9
Assay 2 Contact Irritancy
X ?
Treated screen

• Sand flies exposed for 1 min.
• Butterfly door open for 10 min.

10
Contact Irritancy Assay
11
Assay 3 Spatial Repellency
???
?
Treated screen
Untreated screen

• Choice assay.
• Sand flies released into middle unit, butterfly
  doors opened.
• After 10 min, count number and knockdown in
  each unit.

12
Spatial Repellency Assay
(1) Sand fly movement
(acetone only)
13
Spatial Repellency Assay
(2) Sand fly knockdown
(acetone only)
14
Summary

• Re-designed assay chambers offer a useful tool
  for rapid screening of compounds for toxic,
  contact irritant and spatial repellent properties
  against sand flies.
• Toxic / behavioral responses of sand flies were
  similar to mosquitoes.
• Sand fly mortality was demonstrated for most of
  the compounds tested, e.g. permethrin,
  a-cypermethrin gtgt DDT.
• All compounds demonstrated strong contact
  irritancy (excito-repellency).
• Most compounds tested greatly deterred sand flies
  from entering the treated chamber.

• SS220 and USDA plant derivatives not only
  repellent, but also cause mortality within 24
  hours. Ongoing research to develop repellents
  with this property that may also reduce
  population of biting insects.
• Future studies to determine repellency when
  attractant is present.

15
Acknowledgements

• Dr. Nicole Achée, USUHS
• Dr. Kamal Chauhan, USDA
• Elizabeth Broussard, WRAIR
• Mark Brown, USAMMDA
• Deployed War Fighter Protection (DWFP) Program

16
Questions?

• Disclaimer Material has been reviewed by the
  Walter Reed Army Institute of Research. There is
  no objection to its presentation and/or
  publication. The opinions or assertions
  contained herein are the private views of the
  author, and are not to be construed as official,
  or as reflecting true views of the Department of
  the Army or the Department of Defense.