Equine herpes virus update: April 4, 2008

The equine ward at the WCVM's Veterinary Teaching Hospital. Photo: Debra Marshall.

Veterinarians at the Western College of Veterinary Medicine suspect that the neurologic form of equine herpes virus type 1 (EHV-1) has affected four more horses at a Saskatoon-area farm.

Testing is underway to verify a diagnosis in one of the farm’s horses that was euthanized due to severe neurologic signs. Three of its herdmates are showing milder clinical signs of the disease and are also being tested for EHV-1. The farm’s owners have restricted horse traffic on and off their property.

According to the farm’s owners, horses from the newly-affected farm may have had contact with infected horses before clinical disease was evident. This suggests that these newly-suspected cases are still linked to the initial outbreak of EHV-1.

WCVM suspended non-emergency equine clinical services at its Large Animal Clinic in mid-March following admission of two local horses that proved to be suffering from EHV-1 infection. These horses were discharged last week and returned to the local riding stable where the first cases of the viral infection originated.

No new clinical cases of EHV-1 have been confirmed at WCVM’s Large Animal Clinic in the past week, but the veterinary college’s equine admissions are still restricted. Regular equine clinical services at the Large Animal Clinic will resume once diagnostic testing determines that in-clinic horses pose no risk of virus shedding and once the hospital facilities have been thoroughly cleaned and disinfected.

All other activities and services provided by the Veterinary Teaching Hospital and the Western College of Veterinary Medicine — including the ambulatory field service — are operating as usual.

No new cases of EHV-1 have been identified at the riding stable where more than a dozen horses were diagnosed with EHV-1 infection. WCVM field service veterinarians report that 15 affected horses at the stable are recovering. The stable’s owners have kept their facility quarantined since the beginning of the outbreak to control the potential spread of EHV-1 to other farms.

The EHV-1 virus, which is contagious through contact and through aerosols, can be controlled by restricting contact and with stringent decontamination of facilities. EHV-1 can not be transmitted to humans or to other animal species and is not a reportable disease in Canada.

Horse owners are urged to contact their local veterinarian for further information about EHV-1, or if they suspect disease in their own horses. For general information about EHV-1, they can also contact Dr. Katharina Lohmann at the Western College of Veterinary Medicine (306-966-7157 or 306-966-7178).

For more information about the clinical signs, treatment and control of EHV-1, please click on the following links to download fact sheets about the virus.

EQUINE HERPES VIRUS FACT SHEETS
• Information from the American Association of Equine Practitioners (AAEP) with additional input from Dr. Katharina Lohmann: Equine Herpes Virus Fact Sheet.
• Special on line supplement from The Horse (five parts):

• 1. Herpes by the Numbers
• 2. Neurologic Herpesvirus
• 3. Herpesvirus Vaccination
• 4. EHV Latency
• 5. Herpesvirus Management Basics

• Information from the Merck Veterinary Manual.

• “Infectious Disease Control.” By Dr. Katharina Lohmann.