Pilot Study for Assessment of Tires as Breeding Sites in Fairfax County Fairfax County Health Department Brent O Dea O M.S. John Vander Voort Jorge Arias, PhD.
Reasons for Study To determine production capacity of discarded tires Tires are a favored breeding site of the Asian tiger mosquito (Aedes Aedes albopictus) Fairfax County s s number one nuisance mosquito WNV vector Utilize data for public outreach Limited tire site studies in Virginia Image courtesy of CDC
Hypotheses Tires will produce significant numbers of mosquitoes Ae. albopictus will be the dominant species In contrast to tire studies in MD, WV where Oc. japonicus most numerous species
Reasoning Container survey (Jennifer Armistead, 2006) Ae. albopictus made up 55.5% of the larvae detected in tires Other 2006 tire sampling Ae. albopictus larvae 68% Decrease in Oc. japonicus in routine surveillance
Oc. japonicus Decrease in Fairfax Surveillance Efforts Routine Trapping Gravid 2005 Gravid 2006 Gravid 2007 Average Per Trap Night 0.6 0.27 0.23 CDC 2005 CDC 2006 CDC 2007 0.2 0.06 0.11
The Study May 4 th to November 11 th 2007 10 SUV tires - 10 meters apart Behind Fairfax County Health Department
Location of Tires Image courtesy of Fairfax City
Materials and Methods Tires tied in upright position for stability 3 liters of water Dried pin oak leaves
Each week tire contents removed Sampling Third & fourth instars and pupae removed Water, debris, and younger instars returned to tires
Data Collection Larvae and Pupae transferred to breeding chambers Toxoryinchites rutilus removed (n=118) Upon emergence adults killed and identified to male, female and by species
Results Species Composition 2007 (Males and Females n=5585) Oc. triseriatus 11% Ae. albopictus 17% Cx. restuans 18% Oc. japonicus 29% Cx. pipiens 25%
Species Composition 2007 ( Females n=3119) Oc. triseriatus 14% Ae. albopictus 16% Cx. restuans 15% Cx. pipiens 22% Oc. japonicus 33%
Comparison of Cx. pipiens and Cx. restuans Emergence (Female) Avg # of Mosquitoes per week - 10 Tires 10 8 6 4 2 0 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 May June July August EPI Week Sept Cx. pipiens Cx. restuans Oct Nov
Comparison of Ae. albopictus, Oc. triseriatus, and Oc. japonicus Emergence by Week (Female) Avg # of Mosquitoes per week - 10 Tires 20 15 10 5 0 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 May June July August Sept Oct Nov EPI Week Oc. japonicus Ae. albopictus Oc. triseriatus
Comparable to Other Studies Oviposition Study Frederick, MD Oc. japonicus 43% Ae. albopictus 7% (Sardelis & Turell 2001) Abandoned Tire Collection Study WV Oc. japonicus dominant species represented in collections. (Joy & Sullivan 2005)
Possible Importance of Findings Oc. japonicus shown to be a highly efficient vector of West Nile virus (WNV) & La Crosse encephalitis (LAC) in laboratory trials. (Sardelis and Turrel 2001) Breed in catch basins More cold tolerant than Ae. albopictus Over winter & larger range Photo Courtesy H.J. Harlan, AFPMB
Possible Importance of Findings Oc. japonicus range expanding since discovered in 1998 Detected in 27 states
Spread of Oc. japonicus 1998
Spread of Oc. japonicus 1999
Spread of Oc. japonicus 2000
Spread of Oc. japonicus 2001
Spread of Oc. japonicus 2002
Spread of Oc. japonicus 2003
Spread of Oc. japonicus 2004
Spread of Oc. japonicus 2005
Spread of Oc. japonicus 2006
Where are the adult Oc. japonicus? Surveillance Decrease? Lack of an effective surveillance tool Low numbers from Adult surveillance Routine Weekly CDC and Gravid Trap Study
CDC and Gravid Location Image courtesy of Fairfax City
Trap Species Average Per Trap Night CDC (24 Trap nights) Ae. albopictus (n=42) Oc. japonicus (n=5) 1.8 0.2 Gravid (24 Trap nights) Ae. albopictus (n=10) Oc. japonicus (n=10) 0.4 0.4
Four Trap Study (BG, Zumba, CDC, Faye-Prince Collective) Trap Species Average Per Trap Night Trap Study (224 Trap nights) Ae. albopictus (n= 2241) 10.00 Oc. japonicus (n=29) 0.13
Conclusions Tires produced significant number of mosquito larvae Tires produced large number of Oc. japonicus instead of predicted Ae. albopictus Oc. japonicus may be more prevalent than recognized in trapping surveillance Possible concern as could play important role in future arbovirus disease transmission
Considerations What really is going on with Oc. japonicus numbers? Is this a site specific artifact Could the expanded range of Oc. japonicus have future implications on mosquito control? Should larval surveys for Oc. japonicus be a part of local mosquito surveillance?
Further Direction Study to be repeated in 2008 Expanded to second site Utilize other containers
Questions or Comments
Acknowledgements Thanks to: Joshua Smith - assistance in collection and ID Adrian Joye - GIS Maps