Latest Research On Spatial Repellency for Disease Control

1. Latest Research On Spatial Repellency for Disease Control Nicole L. Achee Department Preventive Medicine & Biometrics Uniformed Services University of the Health Sciences 10 February 2010 Pest Management Workshop

2. Current Global Strategies Vector makes contact with a chemical source, absorbs insecticide and is killed = “mortality centric” Uniformed Services University of the Health Sciences

3. Other Strategies Available Behavioral Responses for Breaking Man/Vector Contact Uniformed Services University of the Health Sciences

4. Why Spatial Repellency? The current vector control dogma is: “the only good mosquito is a dead mosquito”. So what is the advantage to the public health community to repel vectors without killing? Immediate impact: minimize potential for insecticide resistance . Long-term benefit: exploitation of yet undescribed events vectors engage in outside the home pre-, during and post-host seeking to further enhance vector control. Such a paradigm shift from toxic to non-toxic strategies will require clear evidence to the scientific community that: 1) Spatial repellency exists as an action separate from irritancy and toxicity 2) A vector control approach using spatial repellency will impact disease Uniformed Services University of the Health Sciences

5. Acquiring Evidence : Identifying Chemical Actions Does spatial repellency exist as an action separate from contact irritancy and toxicity? Dose Responses Uniformed Services University of the Health Sciences

6. Chemical Actions & Vector Responses Uniformed Services University of the Health Sciences

7. Outdoor Trap “PULL” Trap Trap Push-Pull Concept Overview Use minimal dose and targeted coverage (portals of entry/resting sites) to make a house unacceptable Focal Treatment = Contact Irritant “PUSH” Spatial Repellent “PUSH”

8. Behavioral Thresholds in the Field THAILAND • Treated netting placed upon interior walls of experimental huts • Evaluate using mark-release study design with local vector populations • Interception traps capture entering mosquitoes • Time and density of mosquito entry recorded as compared to control hut Uniformed Services University of the Health Sciences

9. Window Behavioral Thresholds in Field THAILAND • Calculate total indoor surface area of hut: • Use 100,75, 50, 25% coverage ratios of treated material at varying doses • Application begins at portal of entry (window) and coverage increases towards center of hut Uniformed Services University of the Health Sciences

10. 3 Repetitions (300 ♀) Total Control = 115 Total Treatment = 63 45% Reduction Spatial Repellency Behavioral Thresholds in Field THAILAND Treatment: 100% surface area of X at ½ FAR Control Hut Treatment Hut Uniformed Services University of the Health Sciences

11. Behavioral Thresholds in Field THAILAND Dose refers to material treatment. No measure of chemical dose in air space – is it a SR effect or KD? Uniformed Services University of the Health Sciences

12. A.I. in Air Column & Behavior THAILAND What is the chemical concentration in air space over distance? Protection range Does this dose elicit SR or KD? Indoors Door Window Window OR Air Sampling Points Uniformed Services University of the Health Sciences

13. Acquiring Evidence: Impact on Disease Will a vector control approach using spatial repellency reduce disease? **Must have entomological correlates** Diversion to Untreated Human-Host Locations Incidence of Malaria Uniformed Services University of the Health Sciences

14. Diversion to Untreated Areas THAILAND Field Station 45 m 45 m Will a SR treated structure cause vectors to move to untreated areas? Shift rather than reduce disease transmission? Hut A Hut D ? Treat Here 45 m 45 m ? Hut B Hut C 45 m ? Uniformed Services University of the Health Sciences

15. Diversion to Untreated Areas THAILAND Baseline Studies Chemical Studies • Total diversion ranged from 3 - 5% during baseline studies (no chemical) . • Post-treatment, percent moving from treated to control was 4.7% - within the range of random movement without chemical. Uniformed Services University of the Health Sciences

16. Diversion to Untreated Areas Hut B Hut A Hut C Hut D Hut E Treat with Repellent Uniformed Services University of the Health Sciences

17. Disease Impact of SRSUMBA ISLAND, INDONESIA Uniformed Services University of the Health Sciences

18. Malaria DynamicsSUMBA ISLAND, INDONESIA Malaria prevalence as high as 40% and 65% among children <5 years Species distribution: 75% P. falciparum, 22% P. vivax, 3% P. malariae Uniformed Services University of the Health Sciences

19. Traditional HomeSUMBA ISLAND, INDONESIA Uniformed Services University of the Health Sciences

20. Malaria VectorsSUMBA ISLAND, INDONESIA Species: An. sundaicus* An. subpictus An. maculatus An. barbirostris An. vagus Challenge I: Low vector densities; difficult to measure behavioral effects Uniformed Services University of the Health Sciences

21. Ambigous Indoor/Outdoor Spaces “Outside” Porch “Inside” Room Challenge II: Open housing structures so must consider 1) site of vector entry and placement of SR product; 2) fluid dynamics on A.I. concentration; 3) entomological collection methodologies Uniformed Services University of the Health Sciences

22. Summary Statements • A clear understanding of vector ecology is essential to the development of novel vector control tools – this includes house entry and exit behavior patterns. • Spatial repellency can serve to prevent vectors from entering a specified space occupied by a human host . Quantifying diversion vital component to strategy implementation and success • Spatial repellency occurs at non-toxic doses and minimal surface area coverage. Chemical gradients over space must be defined to clearly separate SR from Tox • Targeting spatial repellent products at key entry points may increase efficacy. Cost-effective application strategies for development • Defining correlates of vector densities inside a given space with disease transmission must be performed to understand impact factor of a spatial repellent. Evidence of reduced case incidence required to shift a vector control paradigm Uniformed Services University of the Health Sciences

23. Final Words: We Need Additional Tools Uniformed Services University of the Health Sciences

24. Final Words: We Must Consider All Options Goal is to PREVENT disease transmission – she is one of the fortunate ones. He is one of too many who are not. Uniformed Services University of the Health Sciences

25. Acknowledgements • USUHS Lab Team: • HortanceManda • LuanaArce • Pankhil Shah • Tarra Tolbert • Cecilia Coscoran • Jennifer Eckhaus • Thailand Field Team: • TheeraphapChareonviriyaphap • SuppaluckPolsomboon • KranjanaTaichum • SungsitSungvornyothin • MonthathipKongmee • Peru Field Team: • Kirk Mundal - NMRCD • Fanny Castro - NMRCD • Tom Scott - UCDavis • Amy Morrison - UCDavis • Greg Devine – Rothamsted Research • SumbaTeam: • Din Syafruddin – EijmanInsititute • Kevin Baird – Alertasia Foundation • Claus Bogh - Sumba Foundation • Michael Bangs – International SOS • John Grieco -USUHS • Dan Lawson / Maude Meier - SCJ Funding supported by grants from: NIH: “Behavior-Modifying Compounds for Disease Control” Bill & Melinda Gates Foundation: “A push-pull strategy for Ae. aegypti Control” Uniformed Services University of the Health Sciences

26. THANK YOU FOR YOUR ATTENTION Keep updated: http://www.usuhs.mil/pmb/gsvc