Duane J. Gubler, ScD Professor and Founding Director, Signature Research Program in Emerging Infectious Diseases, Duke-NUS Medical School, Singapore

Transcription

1 Duane J. Gubler, ScD Professor and Founding Director, Signature Research Program in Emerging Infectious Diseases, Duke-NUS Medical School, Singapore AGENDA Other arboviruses with the potential for urban emergence Known and potential urban vectors; distribution, ecology, behavior, vectorial capacity, competition Potential for mosquito transmission within the U.S. including by alternate vectors Vector control: history, traditional and new approaches, prospects for the short and long terms 30 30

2 Arboviral Diseases Known to be Transmitted by Aedes (Stegomyia) Species Mosquitoes Dengue Yellow Fever Zika Chikungunya Epidemic Polyarthritis 31 31

3 Severity Other Arboviruses with Potential for Urban Emergence Yellow fever O nyong nyong Spondweni Rift Valley Ross River Japanese encephalitis Bwamba Mayaro Sindbis Probability of occurring Flavivirus Alphavirus Bunyaviridae Intermediate host required 32 32

4 Urban Mosquito Vectors Principal Vector: Aedes aegypti Biology: Day biting Preferentially bites man Highly domesticated Breeds in domestic water containers 33 33

5 Urban Mosquito Vectors Secondary Vector: Aedes albopictus Biology: Day biting Catholic blood feeder Peridomestic-feral Breeds in natural and domestic water containers 34 34

6 Potential Urban/Peridomestic Mosquito Vectors of Zika Virus Pacific and Asia Aedes polynesiensis Aedes hensilii Aedes malayensis Other Aedes scutellaris species Other potential vectors in US Aedes triseriatus 35 35

7 Other Potential Mosquito Vectors 0f Zika Virus? Zika virus isolated in Africa from: Aedes- 20 spp Culex spp Anopheles spp Mansonia spp Eretmapodites spp 36 36

8 Traditional Methods that have Failed to Control Aedes aegypti Space spraying Perifocal control around cases Targeted source reduction Integrated vector management Larval control Community participation Bio-control? Genetic control? Quality control, commitment, approach 37 37

9 SPACE SPRAY Cost: 1.3; Safety: 1.7; Application logistics: 1.7; Speed of application: 1.5; Retreatment interval: 2.9; Availability: 2.5 and to domestic market:

10 Control of Aedes aegypti Past Successes Brazil Global malaria eradication Aedes aegypti hemispheric eradication Singapore Cuba USA & Europe 39 39

11 Aedes aegypti Distribution in the Americas 1930's Adapted from Gubler,

12 Control of Aedes aegypti Reasons for Success Top down, paramilitary programs Dedicated, disciplined and well trained staff Smaller cities and cooperative populations Detailed mapping and control of larval habitats Few automobiles, used tires, plastic containers Economic development Adequate funding Use of good residual insecticide (DDT) 41 41

13 Lessons Learned from Dengue Control Success breeds failure The major drivers of the 20 th century dengue pandemic include: Urban growth in tropical developing countries Lack of effective mosquito control in those cities Globalization Outdoor space spraying of insecticides has little or no impact on transmission Community-based control programs are not effective when used alone 42 42

14 Lessons Learned from Dengue Control Vertically structured programs (Top Down) are effective, but not sustainable Residual insecticides like DDT can be effective in controlling adults emerging from hidden breeding sites Countries with Ae. aegypti must invest in infrastructure to control mosquitoes Emergency response plans must have built-in triggers Sustainability requires government-community partnership Integration of all available tools and technology in a Top Down-Bottom up approach is required for sustainable success Control programs must be regional 43 43

15 Promising New Tools in Mosquito Control Pipeline Lethal Ovitraps New Residual Insecticides Uncertainties Spatial Repellants Sterile Male Release Must be used properly by trained personnel Surveillance for resistance Important to realize that none of these will likely control dengue if used alone IT curtains/screens Wolbachia Viral Interference 44 44

16 Harbourage spraying with residual pyrethroid insecticide Horn Island 45 45

17 Entering a New Era that will Allow Us to Control Arboviral Diseases Using New Tools in the Pipeline Integration Clinical management/ therapeutics Community engagement Vector Control Vaccination Control program Improved Surveillance International mobilization of resources Build public health capacity Fund program implementation Fund research 46 46

18 Critical issues 1. What will be the respective contributions of Aedes aegypti and A. albopictus to ZIKV transmission in the Americas? 2. Will other mosquito vectors play a significant role in ZIKV transmission? 3. Could ZIKV adaptation for more efficient transmission by A. aegypti or other vectors explain its recent emergence? 4. What is the magnitude of risk for mosquito-borne transmission in the U.S.? What regions are at high or low risk? 5. What are the prospects for reducing ZIKV transmission and spread through vector control? Are there new approaches that could be implemented in time to impact this outbreak? 6. What is the role of asymptomatically infected people as amplifying hosts for mosquito transmission? 7. What is the contribution to various potential modes of human-to-human transmission in the current epidemic or in future sites of potential spread (e.g. the U.S.)? 8. What is the potential for ZIKV to establish an enzootic cycle in primates or other vertebrates in the Americas? If enzootic ZIKV circulation becomes established, what will be the long-term impact on human disease? 9. Why is the epidemiological and clinical picture different in the Americas versus endemic and/or enzootic areas of Africa and Asia? 10. What are the priorities for (and limitations) of experimental virus-vector studies? 11. What is the potential importance of vertical transmission by mosquitoes? 12. What are the key vector- and host- related factors determining R 0 that should be subject to priority research? 13. What are the other arboviruses with the potential to emerge into an urban transmission cycle could surprise us in the future, and what should be done to prepare (instead of continuing to respond only after outbreaks are out of control)?