Ohio State University Veterinary Hospital Management of Horses from University of Findlay EHV-1 Outbreak

Admission: Six horses were referred from the University of Findlay for emergency treatment. All horses had signs of neurological disease. One horse was dead on arrival on 19 January 03; this horse went directly to necropsy and was never admitted to the Hospital. Four horses were admitted 18-19 Jan 03. One horse was admitted 28 January 03. All horses were segregated in the old part of the Hospital.
Outcome: All horses admitted to the hospital died between 19 Jan and 1 Feb 03. 

Fever in horses hospitalized at The Ohio State University 18 Jan 03 to 11 Feb 03. (Note: these horses were not from the University of Findlay.) Could these horses have been infected with EHV-1?
Six horses developed fever during this time period. All were tested for EHV-1; preliminary results are as follows:
Acute Serology: 4 horses 1:80 (3); 1:160 (1).
                        2 horses: negative
Convalescent serology pending; as of 2/25/03.
Pharyngeal swab, buffy coat negative
Virus Isolation pending
All of these horses are currently isolated at The Ohio State University Veterinary Clinic.
Probable causes of fever

  • 2 horses: positive for Influenza virus (Directigen test);
  • 1 horse has pleuropnuemonia;
  • 1 horse improving on antimicrobial therapy for a respiratory infection;
  • 1 horse had a postoperative seroma;
  • 1 horse, fever is unexplained. 

Fever and incoordination in horses hospitalized at the Ohio State University Veterinary Hospital 18 Jan 03 to 11 Feb 03.

Four hospitalized horses displayed fever and incoordination during this time period:
One horse was febrile before and during hospitalization, and had a history of cellulites prior to admission to the Hospital. The horse had severe, rapidly progressive incoordination while in the Hospital, and was euthanized. The PCR on respiratory secretions was positive and EHV-1was isolated from central nervous system tissue.
One horse was febrile before admission, had a history of cellulites, and was acutely ataxic in the morning, prior to admission to the Hospital. Work up for incoordination here suggested cervical vertebral osteoarthritis as the cause of the horse’s incoordination. PCR tests were negative. The acute serology sample showed a titer of 1:80. Convalescent serology and virus isolation tests are pending. This horse is very unlikely to have had EHV-1 infection.
One horse became febrile 1 day after discharge, and was incoordinated 8 days after discharge. Incoordination progressed to recumbency, and the horse was euthanized. The PCR test in was positive in the buffy coat; virus isolation is pending. The acute serology sample was positive at a titer of 1:80. (This horse was in Van Wert County, Ohio.)
One horse developed fever and limb edema 1 day after discharge, and was moderately incoordinated 6 days after discharge. The PCR on buffy coat was negative and the acute serology sample was positive at a titer of 1:40; convalescent serology is pending. Virus isolation on blood is pending; a sample of nasal secretions was not obtained on this horse. (This horse is in Western Pennsylvania.) *The second and only other horse on this farm developed fever and neurological signs compatible with EHV-1 infection after contact with the horse discharged from The Ohio State University Veterinary Hospital. This second horse was euthanized at home. EHV-1 has been isolated from the blood of this horse. A necropsy was not obtained. 

Horses in the Ohio State University Veterinary Hospital between 7 January and 13 February 2003
146 horses were hospitalized or seen as outpatients during this period. As of Feb. 12, 2003, every effort was made to contact owners of all such horses. Owners have been told that there is a risk that their horses were exposed to EHV-1 while at the Hospital. We recommended that horses that were at our Hospital be isolated for 21 days. We further suggested that rectal temperatures be taken daily on all horses in contact with the possibly exposed horse. We asked owners to contact us if fever or signs of neurological were noted. All horses now known to have or have had fever or neurological disease are accounted for above.
Strategies for Reducing Risk of EHV-1 Transmission at The Ohio State University Teaching Hospital
No admissions to the Old Hospital have been allowed since 2/12/03.
10 currently hospitalized client horses are isolated in Ward 4 of the Old Hospital for 21 days. 21 Days is 3 times the average infectious period for EHV-1 (7 days).
At the conclusion of the 21-day isolation period for client horses in the Hospital and for research horses in a separate Ward, all horse will be discharged from the Old Hospital and it will be cleaned and disinfected.
Strategies for Reducing Risk of EHV-1 Transmission at The Ohio State University Teaching Hospital
Emergency cases admitted after 2/12/03 were housed in isolation stalls. These horses were never exposed to horses in the Old Hospital.
All horses have been removed from the Galbreath Equine Center and the facility has been cleaned and disinfected.
The Galbreath Equine Center has been functionally separated from the Old Hospital. No cross traffic of personnel, horses or equipment is allowed.
Continuing Service to the Equine Industry at The Ohio State University Veterinary Hospital
The Galbreath Equine Center opened on 2/20/03 for elective patients and emergencies. The Center will function as a stand-alone facility until all the horses have left the Old Hospital and it has been cleaned and disinfected (approximate date, March 24, 2003).

Continuing Surveillance for EHV-1 in the Eastern USA

Clinicians at The Ohio State University field multiple calls daily from concerned practitioners and horse owners. Recommendations for diagnosis and treatment of cases of EHV-1 are available. We will serve as a central repository for information about horses in our area with EHV-1 infection. Information about cases that have confirmed EHV-1 infection will be posted on our Web Site that can be accessed from The Ohio State University Veterinary College Home Page (www.vet.ohio-state.edu/). Select "For the Public" and follow the link to Animal Health Information.
An outbreak of respiratory and neurological disease has been reported during the last 2 weeks in horses at Penn National Racecourse outside of Philadelphia (Grantville), PA. EHV-1 has been isolated from at least one horse. Two horses had neurological signs and have died or were euthanized.
Recent outbreaks of EHV-1 neurological disease in the USA and Canada
Southwestern Virginia, March 1998: Friday et al. Ataxia and paresis with eqine herpesvirus type 1 infection in a herd of riding school horses. J Vet Intern Med 2000:14:197-201.
Johnson County Wyoming, July 2001: The Horse, September 2001;p22.
Northern Virginia, April 2002: TheHorse.com
Ontario Canada: October 2002: TheHorse.com
Canada: January 2003: TheHorse.com
Selected Bibliography
Edington et al. Experimental reactivation of equid herpesvirus 1 (EHV 1) following the administration of corticosteroids. Equine vet J 1985; 17(5);369-372.
Slayter JD, Bochers K, Thackray AM, Field HJ. The trigeminal ganglion is a location for equine herpesvirus 1 latency and reactivation in the horse. J Gen Virol 1994;75 (Pt8):2007-2016.
Van Maanen Equine herpesvirus 1 and 4 infections: an update. Veterinary Quarterly 2002; 24(2):58-78.


About the Author

Catherine Kohn, VMD

Catherine Kohn, VMD, currently at The Ohio State University College of Veterinary Medicine, serves as United States Equestrian Team veterinarian and was the FEI veterinary delegate at the U.S. Olympics in 1996 and at Rolex Kentucky in 1998.

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