Equine Herpesvirus (EHV-1) Situation Report
May 26, 2011
Background
Equine Herpesvirus (EHV-1) infection in horses can cause respiratory disease, abortion in mares, neonatal foal death, and/or neurologic disease. The neurologic form of EHV-1 is called Equine Herpesvirus Myeloencephalopathy (EHM). While EHV-1 and EHM are only officially listed as reportable diseases in some states, private veterinary practitioners are encouraged to notify their State Animal Health Officials of any suspected or confirmed cases, regardless of current official state reporting requirements.
Cases of EHV-1 and EHM have been identified recently in horses that attended the National Cutting Horse Association (NCHA) Western National Championship event in Ogden, Utah held from April 29 to May 8, 2011. The NCHA has notified State Animal Health Officials of horses from their states that were entered in the event and may have been exposed to the virus. State Animal Health Officials have contacted the owners of potentially exposed horses. Standardized recommendations were developed by state and federal officials and are being followed to isolate exposed horses, monitor them for clinical signs of EHV-1, and work with private veterinary practitioners to test and treat horses affected with the disease. Biosecurity procedures have been recommended for premises with suspect and confirmed cases to mitigate further disease spread.
Definitions for This Report
Primary Exposed Horses: Horses that attended the Ogden, Utah event from April 29 to May 8.
Secondary Exposed Horses: Horses that subsequently came into direct contact with horses that attended the Ogden, Utah event.
Tertiary Exposed Horses: Horses with three degrees or more separation from direct contact with a horse that attended the Ogden, Utah event.
Exposed Premises: Premises with exposed horses.
Suspect EHV-1 case: A horse exposed to EHV-1 that develops fever (rectal temperature above 101.5 oF), but has no neurologic signs at this time.
Confirmed EHV-1 case: A suspect EHV-1 case with laboratory confirmation of EHV-1 infection, but has no neurologic signs at this time.
Suspect EHM case: A horse exposed to EHV-1 that develops neurologic signs. (Posterior incoordination, weakness, recumbency with inability to rise, and/or bladder atony are most commonly seen in EHM cases.)
Confirmed EHM case: A suspect EHM case with laboratory confirmation of EHV-1 infection.
Summary Information on Current Situation
- Owners of horses known to have been exposed in this incident have been contacted by State Animal Health Officials.
- Suspect and confirmed cases are reported to be under voluntary or state quarantine.
- Known exposed horses are reported to be under either voluntary or state quarantine.
- A total of 75 confirmed EHV-1 or EHM cases have been reported in 9 states (AZ, CA, CO, ID, NM, NV, OR, UT, WA)
- Of the 75 confirmed EHV/EHM cases, 58 cases are horses that were at the Ogden, Utah event.
- There are 11 horses associated with this incident that are dead or have been euthanized.
- There are 15 newly identified premises with suspect or confirmed cases identified this reporting period.
Detailed Current Information (as of close of business 5/25/2011)
States not included in the tables below have reported there are no known exposed horses related to this incident currently within their state.
Horse Information:
Horses categorized in EHV-1 or EHM suspect categories or as EHV-1 confirmed in previous reports may change categories based on test results or development of additional clinical signs.
Table 1. Cumulative Total of Confirmed Cases and Fatalities as of close of business 5/25/11
| # EHV-1 Confirmed Cases | # EHM Confirmed Cases | # Dead or Euthanized Suspect or Confirmed Cases | |
| Primary Exposed Horses (at Ogden, UT event) |
33 |
25 |
9 |
| Secondary and Tertiary Exposed Horses |
14 |
3 |
2 |
| Total: |
47 |
28 |
11 |
Table 2. Status of Primary Exposed Horses (attended Ogden, UT event)
| State |
# Primary Exposed Horses (at Ogden, UT) |
# EHV-1 Suspect Cases |
# EHV-1 Confirmed Cases |
# EHM Suspect Cases |
# EHM Confirmed Cases |
# Dead or Euthanized Suspect or Confirmed Cases |
| Arizona |
33 |
3 |
2 |
2 |
1 |
1 |
| California |
59 |
3 |
9 |
0 |
6 |
1 |
| Colorado |
38 |
22 |
9 |
0 |
6 |
2 |
| Idaho |
40 |
7 |
1 |
2 |
3 |
2 |
| Illinois |
1 |
0 |
0 |
0 |
0 |
0 |
| Iowa |
5 |
0 |
0 |
0 |
0 |
0 |
| Minnesota |
18 |
0 |
0 |
0 |
0 |
0 |
| Missouri |
3 |
0 |
0 |
0 |
0 |
0 |
| Montana |
17 |
0 |
0 |
0 |
0 |
0 |
| Nebraska |
7 |
0 |
0 |
0 |
0 |
0 |
| Nevada |
7 |
0 |
1 |
0 |
0 |
0 |
| New Mexico |
13 |
1 |
2 |
1 |
1 |
1 |
| Oklahoma |
1 |
0 |
0 |
1 |
0 |
0 |
| Oregon |
20 |
1 |
4 |
0 |
1 |
1 |
| South Dakota |
4 |
0 |
0 |
0 |
0 |
0 |
| Texas |
26 |
0 |
0 |
0 |
0**
|
0 |
| Utah |
51 |
4 |
1 |
1 |
4 |
1 |
| Washington |
35 |
0 |
4 |
0 |
3 |
0 |
| Wyoming |
37 |
1 |
0 |
0 |
0 |
0 |
| Total |
415 |
42 |
33 |
7 |
25 |
9 |
*Information not available
**One confirmed EHM case previously reported was moved back to its home state of New Mexico and is currently reflected in the New Mexico case report.
Table 3. Status of Secondary and Tertiary Exposed Horses
| State |
# Secondary and Tertiary Exposed Horses |
# EHV-1 Suspect Cases |
# EHV-1 Confirmed Cases |
# EHM Suspect Cases |
# EHM Confirmed Cases |
# Dead or Euthanized Suspect or Confirmed Cases |
| Arizona |
60 |
0 |
8 |
1 |
0 |
0 |
| California |
628 |
0 |
1 |
0 |
0 |
0 |
| Colorado |
78 |
0 |
1 |
0 |
0 |
0 |
| Idaho |
108 |
17 |
2 |
0 |
0 |
0 |
| Illinois |
9 |
0 |
0 |
0 |
0 |
0 |
| Iowa |
53 |
0 |
0 |
0 |
0 |
0 |
| Minnesota |
* |
0 |
0 |
0 |
0 |
0 |
| Missouri |
* |
0 |
0 |
0 |
0 |
0 |
| Montana |
* |
0 |
0 |
0 |
0 |
0 |
| Nebraska |
0 |
0 |
0 |
0 |
0 |
0 |
| Nevada |
20 |
0 |
0 |
0 |
2 |
0 |
| New Mexico |
26 |
1 |
0 |
1 |
1 |
1 |
| Oklahoma |
32 |
0 |
0 |
0 |
0 |
0 |
| Oregon |
120 |
0 |
0 |
0 |
0 |
0 |
| South Dakota |
* |
0 |
0 |
0 |
0 |
0 |
| Texas |
323 |
0 |
0 |
1 |
0 |
0 |
| Utah |
162 |
2 |
2 |
1 |
0 |
1 |
| Washington |
* |
0 |
0 |
0 |
0 |
0 |
| Wyoming |
16 |
0 |
0 |
0 |
0 |
0 |
| Total |
1635 |
20 |
14 |
4 |
3 |
2 |
*Information not available
Premises Information:
Table 4. Exposed Premises Information
| State |
# Exposed Premises |
# Exposed premises with suspect or confirmed EHV/EHM cases (# New premises this reporting period) |
# Exposed premises with no suspect or confirmed cases |
| Arizona |
13 |
5 (1) |
8 |
| California |
34 |
17 (8) |
17 |
| Colorado |
12 |
7 (0) |
5 |
| Idaho |
26 |
8 (1) |
18 |
| Illinois |
1 |
0 (0) |
1 |
| Iowa |
2 |
0 (0) |
2 |
| Minnesota |
6 |
0 (0) |
6 |
| Missouri |
1 |
0 (0) |
1 |
| Montana |
* |
0 (0) |
* |
| Nebraska |
3 |
0 (0) |
3 |
| Nevada |
7 |
2 (0) |
5 |
| New Mexico
|
4 |
3 (1) |
1 |
| Oklahoma |
1 |
1(0) |
0 |
| Oregon |
16 |
3 (0) |
13 |
| South Dakota |
2 |
0 (0) |
2 |
| Texas |
16 |
2 (0) |
14 |
| Utah |
29 |
6 (2) |
23 |
| Washington |
26 |
6 (2) |
20 |
| Wyoming |
45 |
1(0) |
44 |
| Total |
244 |
61 (15) |
183 |
* Information not available
Related articles
- BLM Statement on Outbreak of Equine Herpes Virus (EHV-1) (rtfitch.wordpress.com)
- “NM horse dies from equine herpes virus” and related posts (thewesterner.blogspot.com)
- Stick horses used in contest amid equine outbreak (seattletimes.nwsource.com)
- Horse virus cases double to 75; at least 11 deaths (seattletimes.nwsource.com)
- Horse herpes outbreak forces rodeo queens to ride stick ponies ()
- Equine herpes virus outbreak spooks horse owners (latimesblogs.latimes.com)
- Local horse has equine herpes virus (bendbulletin.com)
- More horse herpes detected in Utah, elsewhere ()
