# Presentation: 628827

## Equine West Nile Encephalitis:The 2002 U.S. Epizootic

**Eileen N. Ostlund, DVM, PhD**
**USDA / APHIS/ VS**
**National Veterinary Services Laboratories**

## Acknowledgments

-    **Data on equine cases of West Nile virus (WNV) infection were acquired through the efforts of private veterinary practitioners, clinicians, field investigators, laboratory diagnosticians, animal health and public health officials in all the States where suspect equine cases have been investigated to date.  **
**	**
**	****	**

## Topics

**2002 equine epizootic**
**WNV laboratory tests veterinary species**
**Update equine vaccine issues**
**Predictions for 2003**

## West Nile encephalitis2002 equine epizootic  

## West Nile Virus 2001 – equine

**MASSACHUSETTS**

**NEW JERSEY**

**CONNECTICUT**

**NEW**** ****HAMPSHIRE**

**FLORIDA**

- MISSISSIPPI

- WEST

- VIRGINIA

- WASHINGTON

- OREGON

- IDAHO

- MONTANA

- WYOMING

- NORTH

- DAKOTA

- SOUTH

- DAKOTA

- NEBRASKA

- IOWA

- MINNESOTA

- WISCONSIN

- ILLINOIS

- INDIANA

- OHIO

- MISSOURI

- KANSAS

- COLORADO

- UTAH

- NEVADA

- CALIFORNIA

- ARIZONA

- NEW MEXICO

- OKLAHOMA

- ARKANSAS

- KENTUCKY

- VIRGINIA

- TEXAS

- GEORGIA

- ALABAMA

- SOUTH

- CAROLINA

- NORTH CAROLINA

- TENNESSEE

- PENNSYLVANIA

**MARYLAND**

- NEW YORK

**VERMONT**

- MAINE

**DELAWARE**

- LOUISIANA

**MICHIGAN**

**West Nile Virus 2001 – equine**

## West Nile Virus 2001all species

**MASSACHUSETTS**

**NEW JERSEY**

**CONNECTICUT**

**NEW**** ****HAMPSHIRE**

**FLORIDA**

- MISSISSIPPI

- WEST

- VIRGINIA

- WASHINGTON

- OREGON

- IDAHO

- MONTANA

- WYOMING

- NORTH

- DAKOTA

- SOUTH

- DAKOTA

- NEBRASKA

- IOWA

- MINNESOTA

- WISCONSIN

- ILLINOIS

- INDIANA

- OHIO

- MISSOURI

- KANSAS

- COLORADO

- UTAH

- NEVADA

- CALIFORNIA

- ARIZONA

- NEW MEXICO

- OKLAHOMA

- ARKANSAS

- KENTUCKY

- VIRGINIA

- TEXAS

- GEORGIA

- ALABAMA

- SOUTH

- CAROLINA

- NORTH CAROLINA

- TENNESSEE

- PENNSYLVANIA

**MARYLAND**

- NEW YORK

**VERMONT**

- MAINE

**DELAWARE**

- LOUISIANA

**MICHIGAN**

**West Nile Virus 2001****all species**

## West Nile Virus Emergency Management Warnings 2002

**MASSACHUSETTS**

**NEW JERSEY**

**CONNECTICUT**

**NEW**** ****HAMPSHIRE**

**FLORIDA**

- MISSISSIPPI

- WEST

- VIRGINIA

- WASHINGTON

- OREGON

- IDAHO

- MONTANA

- WYOMING

- NORTH

- DAKOTA

- SOUTH

- DAKOTA

- NEBRASKA

- IOWA

- MINNESOTA

- WISCONSIN

- ILLINOIS

- INDIANA

- OHIO

- MISSOURI

- KANSAS

- COLORADO

- UTAH

- NEVADA

- CALIFORNIA

- ARIZONA

- NEW MEXICO

- OKLAHOMA

- ARKANSAS

- KENTUCKY

- VIRGINIA

- TEXAS

- GEORGIA

- ALABAMA

- SOUTH

- CAROLINA

- NORTH CAROLINA

- TENNESSEE

- PENNSYLVANIA

**MARYLAND**

- NEW YORK

**VERMONT**

- MAINE

**DELAWARE**

- LOUISIANA

**MICHIGAN**

**West Nile Virus Emergency Management Warnings 2002**

**June 19**

## West Nile Virus Emergency Management Warnings 2002

**MASSACHUSETTS**

**NEW JERSEY**

**CONNECTICUT**

**NEW**** ****HAMPSHIRE**

**FLORIDA**

- MISSISSIPPI

- WEST

- VIRGINIA

- WASHINGTON

- OREGON

- IDAHO

- MONTANA

- WYOMING

- NORTH

- DAKOTA

- SOUTH

- DAKOTA

- NEBRASKA

- IOWA

- MINNESOTA

- WISCONSIN

- ILLINOIS

- INDIANA

- OHIO

- MISSOURI

- KANSAS

- COLORADO

- UTAH

- NEVADA

- CALIFORNIA

- ARIZONA

- NEW MEXICO

- OKLAHOMA

- ARKANSAS

- KENTUCKY

- VIRGINIA

- TEXAS

- GEORGIA

- ALABAMA

- SOUTH

- CAROLINA

- NORTH CAROLINA

- TENNESSEE

- PENNSYLVANIA

**MARYLAND**

- NEW YORK

**VERMONT**

- MAINE

**DELAWARE**

- LOUISIANA

**MICHIGAN**

**West Nile Virus Emergency Management Warnings 2002**

**July 11**

## West Nile Virus Emergency Management Warnings 2002

**MASSACHUSETTS**

**NEW JERSEY**

**CONNECTICUT**

**NEW**** ****HAMPSHIRE**

**FLORIDA**

- MISSISSIPPI

- WEST

- VIRGINIA

- WASHINGTON

- OREGON

- IDAHO

- MONTANA

- WYOMING

- NORTH

- DAKOTA

- SOUTH

- DAKOTA

- NEBRASKA

- IOWA

- MINNESOTA

- WISCONSIN

- ILLINOIS

- INDIANA

- OHIO

- MISSOURI

- KANSAS

- COLORADO

- UTAH

- NEVADA

- CALIFORNIA

- ARIZONA

- NEW MEXICO

- OKLAHOMA

- ARKANSAS

- KENTUCKY

- VIRGINIA

- TEXAS

- GEORGIA

- ALABAMA

- SOUTH

- CAROLINA

- NORTH CAROLINA

- TENNESSEE

- PENNSYLVANIA

**MARYLAND**

- NEW YORK

**VERMONT**

- MAINE

**DELAWARE**

- LOUISIANA

**MICHIGAN**

**West Nile Virus Emergency Management Warnings 2002**

**July 18**

## West Nile Virus Emergency Management Warnings 2002

**MASSACHUSETTS**

**NEW JERSEY**

**CONNECTICUT**

**NEW**** ****HAMPSHIRE**

**FLORIDA**

- MISSISSIPPI

- WEST

- VIRGINIA

- WASHINGTON

- OREGON

- IDAHO

- MONTANA

- WYOMING

- NORTH

- DAKOTA

- SOUTH

- DAKOTA

- NEBRASKA

- IOWA

- MINNESOTA

- WISCONSIN

- ILLINOIS

- INDIANA

- OHIO

- MISSOURI

- KANSAS

- COLORADO

- UTAH

- NEVADA

- CALIFORNIA

- ARIZONA

- NEW MEXICO

- OKLAHOMA

- ARKANSAS

- KENTUCKY

- VIRGINIA

- TEXAS

- GEORGIA

- ALABAMA

- SOUTH

- CAROLINA

- NORTH CAROLINA

- TENNESSEE

- PENNSYLVANIA

**MARYLAND**

- NEW YORK

**VERMONT**

- MAINE

**DELAWARE**

- LOUISIANA

**MICHIGAN**

**West Nile Virus Emergency Management Warnings 2002**

**July 24**

## West Nile Virus Emergency Management Warnings 2002

**MASSACHUSETTS**

**NEW JERSEY**

**CONNECTICUT**

**NEW**** ****HAMPSHIRE**

**FLORIDA**

- MISSISSIPPI

- WEST

- VIRGINIA

- WASHINGTON

- OREGON

- IDAHO

- MONTANA

- WYOMING

- NORTH

- DAKOTA

- SOUTH

- DAKOTA

- NEBRASKA

- IOWA

- MINNESOTA

- WISCONSIN

- ILLINOIS

- INDIANA

- OHIO

- MISSOURI

- KANSAS

- COLORADO

- UTAH

- NEVADA

- CALIFORNIA

- ARIZONA

- NEW MEXICO

- OKLAHOMA

- ARKANSAS

- KENTUCKY

- VIRGINIA

- TEXAS

- GEORGIA

- ALABAMA

- SOUTH

- CAROLINA

- NORTH CAROLINA

- TENNESSEE

- PENNSYLVANIA

**MARYLAND**

- NEW YORK

**VERMONT**

- MAINE

**DELAWARE**

- LOUISIANA

**MICHIGAN**

**West Nile Virus Emergency Management Warnings 2002**

**August 2**

## West Nile Virus Emergency Management Warnings 2002

**MASSACHUSETTS**

**NEW JERSEY**

**CONNECTICUT**

**NEW**** ****HAMPSHIRE**

**FLORIDA**

- MISSISSIPPI

- WEST

- VIRGINIA

- WASHINGTON

- OREGON

- IDAHO

- MONTANA

- WYOMING

- NORTH

- DAKOTA

- SOUTH

- DAKOTA

- NEBRASKA

- IOWA

- MINNESOTA

- WISCONSIN

- ILLINOIS

- INDIANA

- OHIO

- MISSOURI

- KANSAS

- COLORADO

- UTAH

- NEVADA

- CALIFORNIA

- ARIZONA

- NEW MEXICO

- OKLAHOMA

- ARKANSAS

- KENTUCKY

- VIRGINIA

- TEXAS

- GEORGIA

- ALABAMA

- SOUTH

- CAROLINA

- NORTH CAROLINA

- TENNESSEE

- PENNSYLVANIA

**MARYLAND**

- NEW YORK

**VERMONT**

- MAINE

**DELAWARE**

- LOUISIANA

**MICHIGAN**

**West Nile Virus Emergency Management Warnings 2002**

**August 8**

## West Nile Virus Emergency Management Warnings 2002

**MASSACHUSETTS**

**NEW JERSEY**

**CONNECTICUT**

**NEW**** ****HAMPSHIRE**

**FLORIDA**

- MISSISSIPPI

- WEST

- VIRGINIA

- WASHINGTON

- OREGON

- IDAHO

- MONTANA

- WYOMING

- NORTH

- DAKOTA

- SOUTH

- DAKOTA

- NEBRASKA

- IOWA

- MINNESOTA

- WISCONSIN

- ILLINOIS

- INDIANA

- OHIO

- MISSOURI

- KANSAS

- COLORADO

- UTAH

- NEVADA

- CALIFORNIA

- ARIZONA

- NEW MEXICO

- OKLAHOMA

- ARKANSAS

- KENTUCKY

- VIRGINIA

- TEXAS

- GEORGIA

- ALABAMA

- SOUTH

- CAROLINA

- NORTH CAROLINA

- TENNESSEE

- PENNSYLVANIA

**MARYLAND**

- NEW YORK

**VERMONT**

- MAINE

**DELAWARE**

- LOUISIANA

**MICHIGAN**

**West Nile Virus Emergency Management Warnings 2002**

**August 16**

## West Nile Virus Emergency Management Warnings 2002

**MASSACHUSETTS**

**NEW JERSEY**

**CONNECTICUT**

**NEW**** ****HAMPSHIRE**

**FLORIDA**

- MISSISSIPPI

- WEST

- VIRGINIA

- WASHINGTON

- OREGON

- IDAHO

- MONTANA

- WYOMING

- NORTH

- DAKOTA

- SOUTH

- DAKOTA

- NEBRASKA

- IOWA

- MINNESOTA

- WISCONSIN

- ILLINOIS

- INDIANA

- OHIO

- MISSOURI

- KANSAS

- COLORADO

- UTAH

- NEVADA

- CALIFORNIA

- ARIZONA

- NEW MEXICO

- OKLAHOMA

- ARKANSAS

- KENTUCKY

- VIRGINIA

- TEXAS

- GEORGIA

- ALABAMA

- SOUTH

- CAROLINA

- NORTH CAROLINA

- TENNESSEE

- PENNSYLVANIA

**MARYLAND**

- NEW YORK

**VERMONT**

- MAINE

**DELAWARE**

- LOUISIANA

**MICHIGAN**

**West Nile Virus Emergency Management Warnings 2002**

**August 19**

## West Nile Virus Emergency Management Warnings 2002

**MASSACHUSETTS**

**NEW JERSEY**

**CONNECTICUT**

**NEW**** ****HAMPSHIRE**

**FLORIDA**

- MISSISSIPPI

- WEST

- VIRGINIA

- WASHINGTON

- OREGON

- IDAHO

- MONTANA

- WYOMING

- NORTH

- DAKOTA

- SOUTH

- DAKOTA

- NEBRASKA

- IOWA

- MINNESOTA

- WISCONSIN

- ILLINOIS

- INDIANA

- OHIO

- MISSOURI

- KANSAS

- COLORADO

- UTAH

- NEVADA

- CALIFORNIA

- ARIZONA

- NEW MEXICO

- OKLAHOMA

- ARKANSAS

- KENTUCKY

- VIRGINIA

- TEXAS

- GEORGIA

- ALABAMA

- SOUTH

- CAROLINA

- NORTH CAROLINA

- TENNESSEE

- PENNSYLVANIA

**MARYLAND**

- NEW YORK

**VERMONT**

- MAINE

**DELAWARE**

- LOUISIANA

**MICHIGAN**

**West Nile Virus Emergency Management Warnings 2002**

**August 21**

## West Nile Virus Emergency Management Warnings 2002

**MASSACHUSETTS**

**NEW JERSEY**

**CONNECTICUT**

**NEW**** ****HAMPSHIRE**

**FLORIDA**

- MISSISSIPPI

- WEST

- VIRGINIA

- WASHINGTON

- OREGON

- IDAHO

- MONTANA

- WYOMING

- NORTH

- DAKOTA

- SOUTH

- DAKOTA

- NEBRASKA

- IOWA

- MINNESOTA

- WISCONSIN

- ILLINOIS

- INDIANA

- OHIO

- MISSOURI

- KANSAS

- COLORADO

- UTAH

- NEVADA

- CALIFORNIA

- ARIZONA

- NEW MEXICO

- OKLAHOMA

- ARKANSAS

- KENTUCKY

- VIRGINIA

- TEXAS

- GEORGIA

- ALABAMA

- SOUTH

- CAROLINA

- NORTH CAROLINA

- TENNESSEE

- PENNSYLVANIA

**MARYLAND**

- NEW YORK

**VERMONT**

- MAINE

**DELAWARE**

- LOUISIANA

**MICHIGAN**

**West Nile Virus Emergency Management Warnings 2002**

**August 26**

## Slide 17

## August 23

**August 23, 2002**

**August 23**

## August 30

**August 30, 2002**

**August 30**

## September 6

**September 6, 2002**

**September 6**

## September 18

**September 18, 2002**

**September 18**

## September 23

**September 23, 2002**

**September 23**

## November  6

**November 5, 2002**

**November  6**

## Equine WNV Cases by County

**Total cases = 14,740**

**Equine WNV Cases by County**
**2002**

## Comparison of Equine WNV Cases by County

**Comparison of Equine WNV Cases by County**
**	**

**2002                                     2001**

## Slide 26

## Slide 27

## Clinical presentation of Equine WN encephalitis* 

**Weakness (94%)**
**Ataxia (72%)**
**Abnormal Mentation (67%)**
**Increased Body Temperature (65%)**
**Fasciculation (61%)**
**Anorexia (57%)**
**Cranial Nerve Deficits (44%)**
**Teeth Grinding (20%)**

*** data compiled by Maureen Long, DVM, PhD, U of FL**

## Weakness or Ataxia: 100%

| Asymmetrical | 39% |
| --- | --- |
| Front limbs | 15% |
| Hind limbs | 26% |
| Both limbs | 40% |
| Dysmetria | 39% |

## Flaccid Paralysis

| Recumbent | 30% |
| --- | --- |
| Mortality | 65% |

**Can be intermittent**

## Mentation/Behavior Change: 67%

**Nonresponsiveness  Somnolence                          Low numbers of seizures         Persistent or intermittent**

**Not always recumbent **

## WNV Equine Case Fatality Rate
2002

**2002**

**Specific data available from only 10 states; estimate from 1 additional**
**Overall CFR for 10 states was 28.2 percent**
*** ******324 deaths/euthanasias out of 1148 cases ***
*** ******CFR by state ranged from 0 to 53 percent***
**Estimated CFR for 1 state was 33.3 percent**
*** ******About 214 deaths/euthanasias out of 644 cases***
**Combining all data gives estimate of 30.0 percent CFR for 11 states (538/1792)**
*** ******Likely that actual CFR was higher, probably about 33 percent (based on previous years’ experiences)***

## West Nile laboratory tests for veterinary species  

## WNV Diagnostic tests - NVSL	

**Antibody detection**
**MAC ELISA**
**PRNT**

## WNV Diagnostic tests - NVSL	

**Agent detection**
**RT-nested PCR**
**virus isolation**** **

## TaqMan and RT-nested PCR testing of equine brain tissues

|  | TaqMan Positive | TaqMan Negative | Total |
| --- | --- | --- | --- |
| RT-nPCR positive | 5 | 7 | 12 |
| RT-nPCR negative  | 0 | 4 | 4 |
| Total |  |  | 16 |

## WNV / EEE  RT–nested PCRAmplified Regions of Genomes

**WNV**

**EEE**

**248 bp**

**140 bp**

## Tissue Samples Tested byRT-PCR and mRT-PCR

## West Nile virus equine vaccine(s)  

## WNV equine vaccine 

**Killed virus product given conditional license by APHIS / VS / CVB on 1 August  2001, renewed 2002**
**Full license February 2003**
**Over 6 million doses distributed**
**Administration: 2 doses IM 3-6 weeks apart; one annual booster**

## WNV equine vaccinepost-vaccination responses

**WNV specific IgM**
**No IgM response @ 1:400 detected after 1****st**** dose **
**No IgM response @ 1: 400 detected after 2****nd**** dose**
**Neutralizing Antibody**
**Low or undetectable neutralizing Ab titers after 1****st**** dose  **
**Neutralizing Ab after 2****nd**** dose detected in many vaccinates**

## WNV Cases in “Vaccinated” Horses
2002

**2002**

**Given a reported vaccine efficacy of 94 percent in properly vaccinated horses:**
*** ******On average, ~100,000 horses in a State***
*** ******If 20 percent are vaccinated (20,000) and if clinical attack rate is about 4 per 1000, then:***
***80 vaccinated horses should have become ill, but 94 percent (75) would be protected;***
***thus, 5 vaccinated horses would still become clinically ill (vaccine “failures”) in an “average” State in 2002.     ***
**The more vaccinated horses, or the higher the attack rate, the more potential vaccine failures.**

## WNV Cases in “Vaccinated” Horses
2002

**2002**

**Data available from only 8 states**
**71 cases of possible vaccine failure**
*** ******WNV illness onset 21 days or more after proper***
***    ******vaccination protocol ***
*** ******5 states with at least one possible failure:          ***
***    ******FL (44), KY (17), NJ (3), PA (4), VA (3)***
**- 1,201 total equine cases reported**
*** ******3 states reported no vaccinated equine cases: ***
***    ******CT, ID, WA*****	**
**	****	****- only 7 total equine cases reported**

## WNV DNA equine vaccine  

***E. coli ***** plasmid containing the WNV prM and E genes**** **
**Field trials planned **
**CA, KS, KY, MD, OH, OK**** **
**Environmental assessment**

## West Nile virus predictions:   veterinary impact in 2003  

## Slide 46

## WNV Clinical infections per year

## WNV Clinical infections per year

**?**

## What should we expect in the future?

**Areas that have had WNV in horses, will have it again (although in different horses).**
**Additional areas/states will have WNV cases in horses (i.e., the West Coast).**
**Detecting equine cases of WNV will help define areas of WNV activity.**
**Equine illness may be an early indicator in western areas with numerous and efficient bridge vectors (*****Culex tarsalis*****?). **

## What should we expect in the future?

**An increased number of horses will receive WNV vaccine.**** **
**Expansion of facilities for WNV testing will influence number of horses (and other veterinary species) tested.**** **
**Expansion of facilities for WNV testing will impact data collection.**** **
**Additional species will be identified as susceptible to rare clinical illness from WNV infection.**

## Questions?