Wetlands and West Nile

Transcription

1 Wetlands and West Nile Virus: Facts and Fiction - Thilaka Krishnaraj ih

2 Overview of presentation Importance of West Nile Virus (WNV) WNV and TRCA initiatives Importance of vector larval monitoring Results and conclusions

3 West Nile Virus: to date WNV appeared in 2001 in Canada As of 2009 WNV is present in eight Canadian provinces Seasonal epidemic during summer months 12 species of mosquitoes have potential to transmit the disease Humans are incidental and dead-end hosts

4 West Nile Virus and TRCA In Ontario mosquito control efforts to date have focused on two key enzootic vectors of WNV: Culex pipiens and Culex restuans Wetlands as potential WNV vector habitats Due diligence and request from Regional Health Units of Peel, Durham, York and Toronto

5 WNV and TRCA Public education and outreach Collaborations with regional health units Vector larval mosquito surveillance and monitoring

6 Monitoring objectives Species distribution of mosquitoes across TRCA jurisdiction Larval density of vector mosquitoes in various wetlands and selected stormwater management ponds Level of risk that natural wetlands pose to the public

7 Larval Monitoring wetland sites monitored Marshes, bogs, fens and ponds Complaint sites 9 SWMPs were monitored Residential / commercial areas Complaint sites / high # of larvae present

8 Sites Monitored

9 Sampling Method

10 Sampling Method: Know What You re Looking For Trumpeter Swan Mosquito larvae

11 Sampling Method (contd.) Emergent and floating vegetation Debris and margins Standard mosquito dipper was used to collect larvae Use eyedroppers to carefully remove mosquito larvae The number of larvae from each dip was recorded

12 Sampling Method (contd.) Mosquito larvae transported back to lab, reared to fourth instar and identified to species. Average number of larvae for each vector species used to determine level of risk for each site.

13 Risk Ranking System Based on Wada Nil if no larvae per 10 dips Low if between 1-2 per 10 dips Moderate if between 2-30 per 10 dips High if greater than 31 per 10 dips

14 Data Management and Statistical Analyses Abundance: total t number of larvae identified d Species richness: number of species identified Number of vector & non-vector larvae/year One-way ANOVA: total vector in wetlands and SWMPs Data from 30 ponds over 5 years Larvae number averaged/ pond/ year

15 What We Found Non-WNV Carriers WNV Carriers 1. Culex territans 1. Culex pipiens 2. Anopheles earlei 2. Culex restuans 3. Culiseta impatiens 3. Culex salinarius 4. Culiseta morsitans 4. Culex tarsalis 5. Culiseta inornata 5. Aedes vexans 6. Ochlerotatus flavescens 6. Anopheles punctipennis 7. Anopheles 7. Ochlerotatus implicatus quadrimaculatus 8. Anopheles walkeri 8. Psorophora ferox 9. Ohl Ochlerotatus trivittatus i

16 What We Found Wetlands dentified no. of larvae i Total Wetlands Non-vector Wetlands Vector 46.3% 73.5% 71% 53.7% 38.6% 61.4% 81.9% 26.5% 29% 18.1% larvae were identified in 5 years Proportion of non- vectors higher except for % (2006) to 82% (2007) non-vectors Sampling Year No. inside each bar indicates percentage of larvae identified

17 What We Found Wetlands * indicates non-vector species Cx. territans a Ae. vexans (7.7%) non- 7%) vector : 59.1% An. punctipennis (9.5%) An. quadrimaculatus (1.9%) Cx. pipiens (17.8%) Cx. restuans (3.2%) Cx. territans (59.1%)* Key vectors : Cx. pipiens and Cx. restuans 17.8% and 3.2% respectively

18 What We Found SWMPs no.of larvae id dentified Total SWMP Non-vector SWMP Vector 4883 larvae ae were identified in 5 years % Proportion of 13.8% 84.3% 86.2% vectors higher 96% 68.2% than wetlands Sampling Year No. inside each bar indicate percentage of larvae 68.2% (2008) to identified 99% (2007) vectors

19 What We Found SWMPs An. punctipennis (2.7%) Cx. pipiens (84.8%) Cx. restuans (3.5%) Cx. territans (8.1%)* The key vectors: Cx. pipiens and Cx. restuans represent 84.8% and 3.5% respectively. * indicates non-vector species Cx. territans 8.1% 81%

20 ANOVA - Results One-way ANOVA for total vector counts for 30 ponds. Site Type N Mean larvae S.E F ratio P SWMP * Wetlands Mean number of larvae in SWMP were higher than wetlands Mean no. of larvae significantly different b/w SWMP and Wetlands Mean no. of larvae significant different b/w SWMP and wetlands only for Cx. pipiens and Cx. territans

21 Conclusions Facts Wetlands have high species richness and abundance of mosquitoes, however mostly non-vectors SWMPs have a lower richness and abundance & majority are vectors of WNV Abundance of vector species in wetlands is low compared to SWMPs

22 Conclusions Facts (Contd.) Since both wetlands and SWMPs contain occasional isolated pockets of high densities of larvae continuous monitoring is warranted Overall number of high risk sites associated with both wetlands and SWMPs is low

23 Myths Fiction All mosquitoes are carriers of WNV Presence of large number of mosquitoes is always a serious concern for WNV Wetlands pose significantly higher risks than SWMPs

24 Thank You Thilaka Krishnaraj, M.Sc. Toronto & Region Conservation Authority 5 Shoreham Drive Downsview, Ontario M3N 1S4 Phone: ext tkrishnaraj@trca.on.ca Funding Partners