Equine Herpesvirus-1 Myeloencephalopathy

Guidelines for management of the neurological form of EHV-1

• Questions may be directed to Curtis Colwell, NC State Veterinary Hospital (VH) 919-513-6615
• The primary objective of the policy guidelines is to raise the level of awareness and thus reduce the risk of interrupting equine service delivery at the VH, the Equine Health Center (EHC) at Southern Pines, and the Reedy Creek Farm (RCF) through quarantine resulting from admission, or development of a positive EHV-1 neurological case.
• Upon taking a call for an appointment or emergency, the receptionist or house officer should:
  • Ask the owner/agent or referring veterinarian whether the horse has been at home or at a property within the past 30 days and has suffered from, or been in contact with another horse or horses exhibiting fever >101 Fahrenheit (>38.88 Celsius) with NSAIDS or 101.5 Fahrenheit without NSAIDs, plus signs of nasal discharge, coughing, and/or evidence of neurological dysfunction.
  • Advise the owner/agent that on arrival at the facility the horse must remain on the trailer.
• The likelihood is that the horse with suspected exposure will be an otherwise healthy animal that is referred to the orthopedic, podiatry, outpatient radiology, elective soft tissue surgery, theriogenology, or ophthalmology services.
• Although many medical cases are healthy, the probability is that there will be a more in depth history relating to the presenting problem, including the presence of fever and neurological dysfunction.
• All horses presented to the VH, the EHC, or the RCF will have their temperature checked in the trailer before being unloaded, and subsequently will be walked in hand in a straight line and tight circled to assess the degree of coordination.
  • The owner/agent will be advised to take and record the horse’s temperature prior to loading the animal for transport to one of our facilities, in case heat related stress occurs during transport in hot humid weather. The clinician will take this factor into account when deciding the horse’s disposition at the facility.
• Horses with high fevers and/or signs of coughing or mild nasal discharge, with or without neurological deficits should be tested for EHV-1 by PCR diagnostics if there are no other explanations for the signs of disease. Detection of a positive PCR for EHV-1 in such instances should warrant isolation and limited movement of exposed horses.

Medical cases

• A medical case with a fever and prior or current clinical signs or in contact history and any evidence of neurological disease must be examined by a clinician outside the hospital buildings prior to a decision on whether to admit the horse to restriction or isolation. Presence of these clinical signs may provide supportive evidence of exposure to or reactivation of EHV-1 virus with ensuing neurological signs.
• If the horse is ambulant with signs suggestive of EHV-1, it will be admitted directly to isolation stall 7.  Isolation stalls 5 & 6 are backup options. Horses already in isolation stalls 5, 6, or 7 should be moved to isolation stalls 1-4.
• Other horses with clinical signs suggestive of the neurological form of EHV-1 must be housed in isolation stalls 5 through 7. If these stalls are fully occupied by EHV-1 suspect or positive animals stalls 1-4 should be used.
• If a case is EHV-1 positive on viral testing, quarantine for 21 days and retest using the same system. The isolation facility will be quarantined.
• Length of quarantine is 21 days after the last clinical sign, which is usually temperature, and the horse is EHV-1 test negative (negative for EHV-1 shedding from nasal cavity and NO virus detected in blood).

Diagnostic tests and sample submission

• The VH Micro lab will run PCRs Monday through Friday (8:00 AM to 5:00 PM) and Saturday/Sunday (8:00 AM to 12:00 PM).
  • No special action is needed for weekday sample submissions. Testing will begin when Micro opens M-F if samples are present in the lab and ordered.
  • Samples submitted from Friday 5:00 PM through Sunday, please contact Megan Jacob (307-630-1440) or Melissa Byrd (252-723-0715) to ensure they call in staff to run the samples on Saturday or Sunday.
  • Request types can be:
    • Two nasal or nasal-pharyngeal synthetic swabs without wooden handle submitted in red tube.
      • Swab samples should be stored in the red top tube without additives or liquid.
    • 10mL EDTA blood, extract processed buffy coat.
  • Both sample types can be submitted as one request, priced for up to two samples, as long as they are submitted for processing at the same time.
    • If samples are submitted at different times, they will be processed as two separate samples and thus need two different requests.
  • Samples can be placed in the brown refrigerator across from Cytology, or handed to Micro lab staff directly.
  • All reasonable attempts will be made to finalize the PCR within 24 hours of acknowledged notification.

Use of isolation

• All standard isolation protocols apply with the below modifications
  • Any individual that enters the stall or comes into contact with the patient will not re-enter the EFAVC main facility, until after a shower and complete garment change. This must occur off campus or in a campus building other than the EFAVC, such as the Research Building.
  • Treatment plans should be developed around the above standard to facilitate major treatment times at shift change, so technical staff can leave immediately following treatments.
  • Any breach of protocol should be immediately reported to the attending clinician, the EFAVC Operations Manager, and the EFAVC Epidemiologist; quarantine of the potentially contaminated facility shall be implemented.

Quarantine – confirmed cases

• Once a positive horse is identified either voluntary or state quarantine should be imposed
• Length of quarantine – 21 days after LAST clinical sign which is usually temperature
• Expect quarantine to last 28 to 35 days
• Discharge test requirements – negative for EHV-1 shedding from nasal cavity and NO virus detected in blood
• The owner/agent of the EHV-1 suspect should receive advance notice that they will be required to sign a waiver at admission agreeing to their liability for all additional charges incurred at the VH (or EHC) if the facility is put under voluntary or state quarantine in the event that their horse is a positive EHV-1 neurological case. Quarantine for the admitted case can be expected to last 28 to 35 days. Charges will include required diagnostic testing.
• The owners of other horses in isolation at the time that a suspect animal is confirmed to be EHV-1 positive will not be liable for the additional hospitalization charges incurred through the imposition of quarantine. However, they will be liable for the medical, supportive and level of care charges that would be incurred in the normal management of the problem necessitating admission to isolation.

Quarantine of the main hospital facility

• The entire EFAVC facility will be quarantined in cases where a breach in isolation protocol is observed, the patient enters the main facility, or the state veterinarian suggests/institutes quarantine.
• Quarantine time for all hospitalized patients is 14 days, following the last breach.
• Attending clinicians are responsible for contacting owners to discuss the quarantine.
  • All communications should be recorded in the client communication log.
• All patients in the quarantined facility will be handled with boots and gloves as standard ppe.

NOTE

• Real-time PCR results indicate the presence or absence of viral DNA in the specimens tested, but do not predict clinical outcome.
• Molecular assays to differentiate between neurogenic and non-neurogenic strains have been developed and used for research purposes only. Additional validation will be necessary before use of these assays for diagnosis.
• The interpretation of PCR viral detection for EHV-1 should be done only in the context of the presenting clinical signs for disease in the horse being tested.
• The significance of a positive PCR in an asymptomatic horse is unknown.