# Presentation: 498321

## 2004 West Nile Virus Response

**in Mesa County, Colorado**
- Steven L. DeFeyter
- Director of Environmental Health
- Mesa County Health Department

- Grand Mesa
- Mesa County, Colorado

## 2002

**2002**

## SLC

- UT

- CO

- AZ

- NM

- DEN

- ALB

## INDEPENDENCE ROCK

- Colorado National Monument

## Gunnison River

- MESA CO SENTINEL
- Mosquito Trapping Site
- ME3

- Colorado River

## CITY OF GRAND JUNCTION

## 2003

- 19 Cases
- 2 Deaths

- N = 2,947

## 2004

- N = 292

- 127 CASES
- 3 DEATHS

## 2004 WNV Plan

- WNV Surveillance
- Public Education/“Fight The Bite”
- Biological Mosquito Control
- Backyard Larviciding Campaign
- Storm Sewer Catch Basin Treatments
- MC Mosquito Control Team Hot Zone – Bti
- Grand River MCD - $65K Bti/Methoprene

## Grand Junction

- Fruita

- Palisade

- Whitewater

- Grand River Mosquito Control District

- 2003 Annexation (Funding Available in 2005)
- 28,169 Acres

## 2004 MCHD WNV Surveillance Data

- Culex
- Mosquito
- Totals

- Mosquito Trap Results
- ME1 – ME6

- Situation on July 22nd

- + C
- 7/1

-  + M
-  6/16

- + H Case 7/13

- Public Health  Emergency  Declared on 7/22

- Week #

- Program Begins May 1st

## PLAN  “B”

## Dynamic Aviation, Bridgewater, VA

- King Air 90 Twin PT6A-20 Turbine Aircraft
- Night Vision Gear/Agnav DGPS
- Naled/Dibrom @ .75 oz/acre
- Approx. 35,000 Acres/night

## Slide 14

## Slide 15

## Slide 16

## A1 = 62,505 Acres

**A1 = 62,505 Acres**

## A2 = 73,905 Acres

**A2 = 73,905 Acres**

## A3 = 74,506 Acres

**A3 = 74,506 Acres**

## Spray Effectiveness Indicators

- Massive reduction in mosquito populations
- Significant Culex mosquito vector kill
- 95% + bio-assay cage kill after 24 hours
- Decline in WNV + Culex pools
-       “       “  Culex WNV MIR
-       “       “  Human WNV case reports
-       “       “  WNV NID cases
-       “       “  WNV + blood donations

## GRMCD AREA CULEX TRAP AVERAGES

- 8 Geographic Areas/57 CDC Light Traps

- GRMCD
- AREAS

- A1

- A2

- A3

- Area Cx.
- Averages
- Stacked

- 2004 Week #

**Notes:**
Week 30 (7/18) = 25 Cx./Trap Area Average
Week 32 (8/08 = 2.2 Cx./Trap Area Average

## 113 WNV+ CULEX POOLS

- A1

- A2

- A3

- 100 WNV + Pools Prior to A1/A2

- 10 WNV + Pools After A1/A2

- Total pools submitted  = 500

- 9/17 + POOL CONSISTED OF SPECIMENS COLLECTED IN AND & OUT OF SPRAY AREA.

- ME3

- A1

- A2

- A3

**Notes:**

The state’s hot spot in 2004. Note the steady increase over 5 weeks in the IR for C tarsalis. The early C. pipens spike was based on 6 mosquitoes, tested in 3 pools (2 each) with 2 pools being positive. The 7/11 peak of the C tarsalis IR was based on 338 mosquitoes tested in 9 pools, eight were positive.  This pattern and the increasing numbers of human cases resulted in the aerial mosquito spraying that was done at the end of July. Note drop both in mosquito numbers, which did rebound, and more significantly the IR which did not rebound after the first 2 applications.  Mesa County had the highest total number (43% of the state cases and all 3 deaths) and case rate in 2004 although very few cases occurred after the pesticide applications in July. 

## 2004 WNV Surveillance & Human Cases

- 2004Human/Culex12.27.04.ppt

- W/Human Case Onset Date/Week

- ME1 – ME6
- Reference
- Trap Sites
- Culex
- Totals

- 2004 Week #

- Mesa Co.
- Human Case
- ONSET
- By Week

- A1

- A2

- A3

- 6/1

- 7/1

- 8/1

- 9/1

## 2004 WNV Surveillance & Human Cases

- 2004Human/Culex12.27.04.ppt

- Assumption: WNV Incubation Period = 1 Week

- Reference
- Trap Site
- Culex
- Totals

- 2004 Week #

- Mesa Co.
- Human Case
- INFECTION
- By Week

- A1

- A2

- A3

- ‘03

## WNV+ BLOOD DONATIONS& NEUROINVASIVE DISEASE CASES

- WNV NID CASES
- N = 20

- WNV +
- BD’S
- N = 17

- A1

- A2

- A3

- WNV+ BLOOD DONATIONS& NEUROINVASIVE DISEASE CASES

- 2004 WEEK

## 2004 WNV Summary

- 127 Human Cases/3 Deaths
- 113 WNV + Culex Pools/500 Tested (22.6%)
- Three Aerial Dibrom Applications
- Total Treated Area = 210,916 Acres
- Aerial Adulticiding Cost = $330,940
- Direct Program Cost = $509,780
- CDC ELC/WNV Funds = $116,000

## THE END