Meddleton Equine Hospital

Equine Herpesvirus (EHV-1 or Rhinopneumonitis) 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) and is a sporadic paralytic disease (myeloencephalopathy) secondary to vasculitis of the spinal cord and brain.

Thick Nasal Discharge

Signs of Neurological EHV-1 infection:

• Incoordination
• rear end weakness
• "Dog-Sitting"
• urinary/fecal incontinence

Transmission of EHV-1

• Aerosolized secretions from infected coughing horses
• direct and indirect (fomite) contact with nasal secretions.
• EHV-1 is not transmissible to humans
• Like herpesviruses in other species, these viruses establish latent infection in the majority of horses, which do not show clinical signs but may experience reactivation of infection and shedding of the virus when stressed. Those epidemiologic factors seriously compromise efforts to control these diseases and explain why outbreaks of EHV-1 can occur in closed populations of horses.

Treatment:

Viral infection not responsive to antibiotics, Anti-inflammatory drugs (Banamine), Supportive therapy: IV Fluids, DMSO, sling, Anti-Viral: Valacyclovir (Valtrex) Give when first have signs of infection or before for prevention. Ganciclovir Better once showing clinical signs. Acyclovir – not absorbed well orally

Prognosis:

Poor if unable to stand, Fair to Good if able to stand

Prevention:

• No vaccine labeled for prevention of neurological form. Vaccines have some cross-over protectivity
• Immune Boosters: Equimune, Eqstim, L-Lysine oral supplement

Vaccines:

• Calvenza (Boehringer Ingelheim) IM or IN, Prodigy (Intervet) IM, Rhinomune (Pfizer) IM, Fluvac (Fort Dodge)

Outbreak Mitigation:

• Isolate diseased (28 days past clinical signs) and incoming horses (21 days)
• Vaccination in the face of an outbreak is recommended
• In the face of an outbreak, horses at high risk of exposure may be revaccinated
• Administration of a booster vaccination is likely to be of some value if there is a history of vaccination
• Simple approach: vaccinate all horses in the exposure area—independent of their vaccination history
• If horses are known to be unvaccinated, the single dose may still produce some protection
• Disinfection of premises, equipment, grooming tools, hands, shoes/boots, waterers, feeders, etc 10% Bleach, Roccal-D, etc. Hand Sanitizer
• Restrict Travel. Check State travel restrictions. Up-Do-Date information sources:

OUTBREAK!

National Cutting Horse Association’s (NCHA) Western National Championships at the Golden Spike Event Center in Ogden April 29, 2001 to May 8, 2011

Over 500 horses at the show

• Cases of EHV-1 and EHM were identified 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 notified State Animal Health Officials of horses from their states that were entered in the event and may have been exposed to the virus
• Many horses were at the show for training or sale and were not actually entered into the show. There is no record of those horses
• State Animal Health Officials contacted the owners of potentially exposed horses
• All Suspect and confirmed and exposed horses cases were put under voluntary or state quarantine
• 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

The outbreak was very quickly contained and did not spread to other circles like hunter/jumper or race horses perhaps because the news spread quickly. Everyone shut barns down and stopped public events. Many, many horse events were cancelled in New Mexico

As of June 23, 2011 The USDA reported:

• There are no new cases and no new premises affected.
• Disease spread in connection with this incident has been contained.

EHV-1 Outbreak Summary Information

• A total of 90 confirmed EHV-1 or EHM cases were reported in 10 states (AZ, CA, CO, ID, NM, NV, OK, OR, UT, WA).
• Of the 90 confirmed EHV/EHM cases, 54 cases were horses that were at the Ogden, Utah event.
• There are 13 horses associated with this incident that are dead or have been euthanized.

New Mexico:

New Mexico had two confirmed cases of EHV-1/ EHM that survived and two other confirmed horses that were euthanized (one horse was sent to West TX for Treatment and euthanized there).

• All New Mexico cases were in horses that were at the NCHA event in UT, or stabled with horses at that event.
• Thirteen horses from New Mexico had known exposure.
• New Mexico had 4 premises out of 242 with exposure to horses with EHV-1.
• New Mexico had 13 Primary Exposed Horses (attended Ogden) out of 421. 2 confirmed EHV-1, 1 confirmed EHM, and 1 dead.
• New Mexico had 26 out of 1685 Secondary and Tertiary Exposed Horses, with 1 confirmed EHM and one dead.