Abundance of West Nile Virus Mosquito Vectors in Relation to Climate and Landscape Factors Surrounding Richmond, Virginia Jayne Deichmeister Center for Environmental Studies Virginia Commonwealth University December 2008
Municipal Surveillance Programs Aim to reduce disease risk by Source reduction Larvacide treatment Population monitoring WNV testing Public outreach GIS mapping helps locate and prioritize surveillance sites
Hypotheses Abundance increases arbovirus activity Urbanization increases vector abundance Precipitation increases vector abundance
My Study To examine the effect of climate variables Temperature Precipitation And landscape variables Canopy cover Building Footprint Drainage Infrastructure On the abundance of local vector species Culex pipiens Culex restuans Aedes albopictus
Methodology Temperature and precipitation data from the National Climate Data Center Larval surveillance Henrico County, VA Adult trapping and species identification Study Site: LEGEND Landscape factors mapped through GIS Trap Site with 200 m buffer Stormwater Structures Buildings N 2005, 2006, 2007
CDC Light Baited Trap CDC Gravid Trap
Surveillance of Stormwater Drop Inlets
Methodology Data Analysis Landscape Is there a difference in WNV results between urban and suburban neighborhoods? Chi-square Analysis Is vector abundance correlated with positive WNV testing? Logistic Regression Climate Does temperature, precipitation or vector abundance vary significantly from year to year? One-way ANOVA Is there a difference in environment between urban and suburban neighborhoods? Paired T-Tests Are certain environmental factors correlated with higher vector abundance? Linear Regression Is temperature or precipitation correlated with vector abundance? Linear Regression
Vector Abundance WNV Test Result 1.00 0.75 0.50 0.25 0.00 1 0 0 10 20 30 40 50 60 70 80 Ave mosquitoes caught Vector abundance by WNV test result highly significant N=73 Chi-sq = 14.36 p = 0.0002
Larval Surveillance of Stormwater Structures 1.0 0.8 0.6 0.4 0.2 0.0 Juvenile Observation: Both Species Early Instars Late Instars Pupae 6/25/2008 7/3/2008 7/11/2008 7/18/2008 7/25/2008 8/1/2008 8/8/2008 8/15/2008 8/22/2008 9/5/2008 9/12/2008 9/19/2008 9/29/2008 Average P ro p o rtio n o f D ro p In le ts w ith M o sq u ito es P re s en t 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0.0 6/25/2008 7/2/2008 7/9/2008 7/16/2008 7/23/2008 7/30/2008 8/6/2008 8/13/2008 8/20/2008 8/27/2008 9/3/2008 9/10/2008 9/17/2008 9/24/2008 Proportion of Drop Inlets with Mosquito Adults Present Adult Observation Cx spp. Aedes albopictus
Temperature and Precipitation 2005 Precipitation cm) 10 8 6 4 2 0 a 25 30 35 40 Week 150 125 100 75 50 25 0 Abundance # mosquitoes) Temperature ο C) Precipitation Vector Abundance Temperature
Temperature and Precipitation 2006 20 15 10 5 0 b 100 Precipitation cm) 80 60 40 20 0 25 30 35 40 Abundance # mosquitoes) Temperature ο C) Week Precipitation Vector Abundance Temperature
Temperature and Precipitation 2007 10 8 6 4 2 0 c Precipitation cm) 150 125 100 75 50 25 0 Abundance # mosquitoes) Temperature ο C) 25 30 35 40 Week Precipitation Vector Abundance Temperature
All Years Precipitation cm) 3.5 3.0 2.5 2.0 1.5 60 d 40 20 0 Abundance # mosquitoes) Temperature ο C) 2007 2006 2005 Precipitation Vector Abundance Temperature
Landscape Results Urban Suburban P-value Stormwater Structures 89.3 56.8 0.0058 Building Footprint ) 31.2 23.2 0.0037 Canopy Cover ) 80.3 62.4 0.0911 Avg Cx. pipiens Abundance 40.9 21.3 0.0029 Avg Ae. Albopictus Abundance 11.1 24.18 0.1779 Urban Suburban P-value West Nile Virus Positive ) 3.9 1.4.0094
Culex spp. Ave pipiens 80 70 60 50 40 30 20 10 0 0 50 100 150 200 Number of Stormwater Structures Cx. pipiens, Cx. restuans and stormwater drop inlets r² = 0.21 p= 0.023 Ave pipiens 80 70 60 50 40 30 20 10 0 10 15 20 25 30 35 40 45 50 Percent Building Coverage Cx. pipiens, Cx. restuans and building coverage r² = 0.09 p= 0.078
Discussion Individual roles of temperature and precipitation are somewhat unclear Suggested correlation with drought Possible confounding factor: larvacide application
Discussion Cont. Urbanization correlated with: higher Culex spp. abundance More WNV positive mosquitoes Sampling in stormwater drains provides evidence that mosquitoes are using them as a habitat all season long
Acknowledgements Henrico County Public Works Department Lane Carr Randy Buchannan Aparna Telang Peter defur Jeff Sullard Michelle Fults John Frey Jon Swanson Jennifer Jones Kevin Caillouet Frank Deichmeister Elizabeth Macklin