Evidence Based Considerations for Adult Mosquito Control

Transcription

1 Evidence Based Considerations for Adult Mosquito Control Curtis Russell Senior Program Consultant Enteric, Zoonotic, & Vector Borne Diseases

2 Outline Ontario Background WNV Background Development of Guide Adulticiding Window Discussion 2

3 3 recensement/2006/as sa/97 550/vignettes/img/map 2006 pop density ontario sz01 en.gif

4 Culex pipiens/restuans The primary vectors for WNV in Ontario

5 Mosquito Surveillance (Trapping) CDC Miniature Light Trap Attracts host seeking adult mosquitoes. Larval Dipping Looking for larvae in their aquatic habitat.

6 Location of West Nile Virus positive mosquito pools in Ontario, Cumulative Positive Pools Data source: PHO mosquito database, extracted [2013/02/21] 6

7 Geographic distribution of WNV cases by health unit of residence: Ontario, 2002, 2005, 2011, Data source: Ontario Ministry of Health and Long Term Care, iphis database, extracted by Public Health Ontario [2013/02/21].

8 Mosquito Control in Ontario There are three larvicides currently approved for WNV control in Ontario: 1. Bacillus thuringiensis israelensis (Bti) 2. Bacillus sphaericus (B. sphaericus) 3. Methoprene The only adulticide product currently approved for use in Ontario is malathion.

9 2010

10 What is Adulticiding?? 10

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12 WNV Activity in Ontario 12 Data source: Ontario Ministry of Health and Long Term Care, iphis database, extracted by Public Health Ontario [2013/02/21]. PHO mosquito database, extracted [2013/02/21]

13 Google Trends Keywords: West Nile Virus, for Ontario 13

14 Development of Guide Conducted literature search focusing on triggers for mosquito control Comparison to other jurisdictions and Canada and USA Formed working group involving health units, the Ministry of Health and Long Term Care, and the Ministry of the Environment Sought input on local knowledge and experience Each health unit has their own perspective and level of activity for action 14

15 Ontario has never adulticided for WNV Working Group Discussion No specific indicators, or WNV activity levels, have been identified in Ontario that reliably indicates the need for adulticiding Human WNV cases may drive the decision to adulticide The decision to adulticide will be based on a variety of imperfect surveillance data sources The decision to adulticide can only prevent WNV transmission events that are anticipated to occur at least one week after a decision to adulticide is taken 15

16 Temperature Accumulated Degree Days (ADD) Effects of previous seasons Human Behaviour Testing/Reporting Prevention Other Mitigation Factors: Larviciding Source Reduction Public Education Factors Influencing WNV Seasonal Activity 16

17 Seasonal Measurements Mosquitoes and Seasonality Human WNV Cases Vector Index Accumulated Degree Days (ADD) 17

18 Mosquito Seasonality and Human Cases 18

19 WNV Human Cases: Ontario, Average Number vs & Data source: PHO mosquito database, extracted [2013/02/21]

20 Total Accumulated Degree Days 2012 Data source: PHO mosquito database, extracted [2013/02/21]

21 WNV Activity in Ontario 21

22 Average Accumulated Degree Days (southern ON) vs Data source: PHO mosquito database, extracted [2013/02/21] 22

23 Vector Index VI = Σ NiPi i=species N = average number of mosquitoes per trap, P = estimated infection rate The Vector Index is the estimate of the number of infected mosquitoes caught per night. The Vector Index is therefore an estimate of the number of infected mosquitoes to which humans or animals would be exposed per night, in a given week at a given site. Works better in years with higher activity and areas with more mosquito traps 23

24 Adulticiding Window Want to spray before the peak in human cases May take a week of preparations before able to spray Public notification May take more than one night to spray May need multiple treatments 24

25 Discussion Assessing WNV risk requires consideration of multiple factors Ontario has had few years with high WNV activity levels No current reliable and validated predictive model of WNV risk PHO working with York University to investigate potential models and their feasibility 25

26 Acknowledgements Ministry of Health and Long Term Care Ministry of the Environment City of Hamilton Public Health Services Durham Region Health Department Halton Region Public Health Middlesex London Health Unit Niagara Region Public Health Ottawa Public Health Peel Public Health Region of Waterloo, Public Health Simcoe Muskoka District Health Unit Toronto Public Health Windsor Essex County Health Unit York Region Public Health 26