# Presentation: 321585

## West Nile Virus Surveillance and Control in the  SYMVCD

- David Brown1, Dia-Eldin Elnaeim1, and Ryan Carney2
- 1Sacramento-Yolo Mosquito and Vector Control District
- 2California Department of Health Services

**Notes:**
Challenges of mosquito control Districts to use control strategies that minimize impacts to wildlife resources
My name is David Brown, Manager of the Sacramento-yolo Mosquito and Vector Control District.

## Slide 2

## District Developed WNV Response Plan  

- Updated plan with Board of Directors  January-March 2005
- Utilized California Mosquito-Borne Virus Surveillance and  Response Plan and CDC Guidelines
- Five Levels of Control
- Level 1  - Basic Level
- Level 2  - Mosquito Pool/dead bird
- Level 3  - Animal/Chicken
- Level 4  - Human case
- Level 5  - Epidemic conditions

## Basic Level of Mosquito Management Measures

- Thresholds are
- 100 mosquitoes in MMT/ EVS per trap night    or
- 25 mosquitoes in Light /Gravid per trap night
- Source Reduction/ Water Management
- Biological Control
- Larvicide (immature mosquito) control
- Adulticide (mature mosquito) control in Rural/Agricultural/open space areas
- Education

## When Response Plan Triggered  

- Mosquito Abundance Thresholds are Lowered  and District Response Increases
- Lab staff determines scope of infections
- Control operations maximize larval control
- Immediate treatment of all larval sources
- Localized Treatment for adult control
- Immediate Press Releases to inform public

## WNV Mosquitoes of Concern 

-  2 species very efficient
*Culex tarsalis*
- Agriculture
- Natural Sources
- Urban
*Culex pipiens*
- Urban sources
- Dairy/Rural

*Cx. pipiens* ~1 mile
*Cx. tarsalis* ~ 5 miles

- Flight Range

## 2005 Sequence of Events

- By February, already at level 2 (Dead Birds)
- Above Average Rainfall (Through June)
- Followed by Above Average Temperatures  (record July )

## Precipitation Records: Sacramento-Yolo Counties 2000-2005

## Temperature Records: Sacramento-Yolo Counties 2000-2005

## Enhanced Larval Control in Entire Area

- Performed when dip counts exceed 0.1 larvae
- Bti / Bs
- Insect growth regulators
- Light film oils
-  60,000+ treatments to date in District
- 10 additional Technicians  (Swat Team) hired to perform control

## 2005 Sequence of Events, Cont.

**June 29th infected mosquito pools**
**July 15****th**** infected Sentinel Chickens**
**July 21st report of human infection in Sacramento County **
**Media Announcements made at each event**
**July 27****th**** CCC hired to go door-to-door to inform residents of localized adult control**

## The 2005 Sac-Yolo Counties Monthly Dead Birds Reports

**46% (78/168) of**
** ****submitted dead birds**
**were WNV +ve**

##  WNV positive and and negative mosquito pools in June 2005: 4 +ve and 109 -ve 

** ****WNV positive and and negative mosquito pools in June 2005: 4 +ve and 109 -ve**** **

##  WNV positive and negative mosquito pools in July 2005: 70 +ve and 310 -ve 

** ****WNV positive and negative mosquito pools in July 2005: 70 +ve and 310 -ve**** **

##  WNV positive and and negative mosquito pools in August 2005: 53+ve and 503 -ve 

** ****WNV positive and and negative mosquito pools in August 2005: 53+ve and 503 -ve**** **

## Sacramento Mosquito Minimum Infection Rates 

- Sacramento Mosquito Minimum Infection Rates
- (Late July- Early August)

## Aerial Adult Mosquito Control initiated

- Decision made August 4 to treat 50,000 acres North of American River August 8 (3x)
- 70,000 acres south to follow August 11 (3x)*
- 21, 22, 23
- Pyrethrin/PBO product selected at 0.66 oz. per acre
- 330,000 acres=$666,000

## Aerial Spraying zones in North and South Sacramento

## Slide 19

## Held Town Hall Meetings

- Ranging from mild protest.....

## ....to overall acceptance

**...****.to overall acceptance**

## Even Spent a day in Court!

- Started to treat August 8th,
- Sued on August 9th  for
- Alleged violations of the
- Clean Water Act
- Restraining order denied

## Results 

- Significant reduction in Mosquitoes and WNV Infection in North Sacramento County
- Post trap counts showed a dramatic reduction of mosquito population and elimination of WNV  infection

## American Light Trap collection of Culex pipiens in Sacramento-Yolo Counties, 2000-2005

## Effects of aerial spraying of pyrethrin insecticide on numbers of Culex mosquitoes and their infection rates with WNV, in North Sacramento (June – Oct 2005)

**After Spraying**

**Before Spraying**

**Effects of aerial spraying of pyrethrin insecticide on numbers of *****Culex *****mosquitoes and their infection rates with WNV, in North Sacramento (June – Oct 2005)**

## WNV infection rates in Culex mosquitoes collected in North Sacramento before and after aerial spraying with pyrethrin insecticide

**WNV infection rates in *****Culex *****mosquitoes collected in North Sacramento before and after aerial spraying with pyrethrin insecticide**

**After Spraying**

**Before Spraying**

## Fluctuations of mosquito densities and their infection rates with WNV in Non-Sprayed areas in Sacramento and Yolo Counties, during June-Oct 2005

**Fluctuations of mosquito densities and their infection rates with WNV in Non-Sprayed areas in Sacramento and Yolo Counties, during June-Oct 2005**

## Slide 28

## Utilizing the spatiotemporal DYCAST system to predict human West Nile virus cases in California and to evaluate the efficacy of aerial adulticiding within Sacramento County, 2005

**Utilizing the spatiotemporal DYCAST system to predict human West Nile virus cases in California and to evaluate the efficacy of aerial adulticiding within Sacramento County, 2005**

**Ryan M. Carney***WNV Dead Bird Surveillance**Program Coordinator* **California Dept. of Health Services****rcarney@dhs.ca.gov****510 412-6254 phone****510 412-6263 fax**_*HOTLINE:*_* 1-877-WNV-BIRD*_*WEBSITE:*_* westnile.ca.gov*

**62:**

## DHS Analysis of Spray Efficacy on Human WNV Case Reduction

- Contiguous non-sprayed (“control”) areas were defined around the spray zones that were similar demographically and epidemiologically:
- Census 2000 data layer: Housing Density Classes 9-10
- Both sprayed and non-sprayed areas had to have a similar number of human cases *before* the spraying took place
- Epidemiological congruency was further tested through analysis of localized D.Y.C.A.S.T. risk profiles

## Aerial Spray versus “Control” Zones

**SPRAY**

**CONTROL**

_**Spray vs Control Zones**_
**2.5 X  population**
**2.0 X  area**

## WNV Incidence (per 100,000) within Sac Co Study Areas, 2005

- 24       25       26       27      28       29       30       31       32       33       34       35       36      37       38       39       40       41      42       43       44

**DISEASE WEEK**

**NORTH SPRAY****      ****SOUTH SPRAY**

## WNV Incidence (per 100,000) within Sac Co Study Areas, 2005

- 24       25       26       27      28       29       30       31       32       33       34       35       36      37       38       39       40       41      42       43       44

**DISEASE WEEK**

**NORTH SPRAY****      ****SOUTH SPRAY**

## WNV Incidence (per 100,000) within Sac Co Study Areas, 2005

- 24       25       26       27      28       29       30       31       32       33       34       35       36      37       38       39       40       41      42       43       44

**DISEASE WEEK**

**NORTH SPRAY****      ****SOUTH SPRAY**

## WNV Incidence (per 100,000) within Sac Co Study Areas, 2005

- 24       25       26       27      28       29       30       31       32       33       34       35       36      37       38       39       40       41      42       43       44

**DISEASE WEEK**

**NORTH SPRAY****      ****SOUTH SPRAY**

***NO NEW HUMAN CASES***
***WITHIN THE SPRAY ZONES***

## WNV Incidence (per 100,000) within Sac Co Study Areas, 2005

- 24       25       26       27      28       29       30       31       32       33       34       35       36      37       38       39       40       41      42       43       44

**DISEASE WEEK**

**NORTH SPRAY****      ****SOUTH SPRAY**

## Treatments Were Successful, but There Are Issues To Address	

_**CURE WORSE THAN DISEASE**_
- PBO listed as “possible cancer causing agent”
- WNV _not that serious of a disease_
- “Disease affects only those over 50....they do not reproduce nor are they long for the world anyway”

## Further Information	

- _[www.fightthebite.net](http://www.fightthebite.net/)_
- 1-800-429-1022