Wisconsin Equine Herpes Cases:
State of the State

Follow-Up Questions

These answers were provided on Apr 12, 2024, with the information available at that time.

Questions were submitted to the WVMA and answered by the following:

  • Julie Ann McGwin, DVM, Dept of Agriculture, Trade and Consumer Protection
  • Heather Roney, DVM, Dept of Agriculture, Trade and Consumer Protection
  • Simon F. Peek, BVSc, PhD, DACVIM, UW School of Veterinary Medicine
  • Keith Poulsen, DVM, PhD, DACVIM, Wisconsin Veterinary Diagnostic Laboratory

Additional questions may be directed to:
Heather Roney, DVM
Program Veterinarian, DATCP
(608) 590-5997

Keith Poulsen, DVM, PhD, DACVIM
Executive Director, WVDL

Simon Peek, BVSc, PhD, DACVIM, MRCVS
Department of Medical Sciences, UW School of Veterinary Medicine

Q: If a veterinarian is suspicious that an equine has EHV, but the client is not willing to test, what are our options: to test, to quarantine? Who should be informed, and what will they do about it?
A: The veterinarian should contact the Division of Animal Health regarding their suspicions. Ideally, the premises should adopt a voluntary quarantine with instructions from their veterinarian, although the state veterinary office has the authority and reserves the option of issuing a formal quarantine.

Q: What does the quarantine of these facilities mean? Who is initiating, enforcing, and releasing them? Are onsite visits from DATCP anticipated and utilized?
A: A quarantine for EHM generally means that no equines may enter or leave the quarantined premises, usually for a minimum of 21 days. All equines on the premises should have their temperatures taken twice daily (AM and PM). Any rectal temperature above 101.0˚F or any signs of EHV-1 (including EHM, fever, respiratory signs, or abortions) should be reported. The State Animal Health Official (inspectors and veterinarians from DATCP) initiates, monitors, and enforces the quarantine. Onsite visits from DATCP must be permitted.

Q: If the quarantine is in place until the resolution of symptoms; is that just fever, respiratory symptoms, or does it include neurologic symptoms? How many days after the resolution of symptoms are the facilities and animals released?
A: Symptoms of EHV-1 include fever, respiratory signs, abortions, or neurologic (EHM) symptoms. In general, the quarantine is in effect for 21 days after the last exposure to the EHM animal or 21 days after the last equine begins showing any signs of EHV-1.

Q: How many of the current cases are connected either by horse movement or human movement?
A: We don’t have all the answers to this question. Remember, EHV-1 can recrudesce spontaneously without any new exposure to contagious equines.

At this point, we have four horses that MAY have connections to two different sales, one sale in Wisconsin and one out-of-state. Another case may be associated indirectly (fomite/human transfer) with a sale.

Remember, a horse may be an inapparent or intermittent shedder and show no symptoms. They can be contagious and never break with symptoms themselves, or they can show symptoms well after the sale.

Q: How complete is the traceback of equines that may have been exposed to any of the positive animals? What is the likelihood there are more animals that have not been reported or identified from the known existing reported animals and locations?
A: We are doing our best to conduct tracebacks. As you can imagine, it is not easy. There is always the possibility, even likely, that all cases are not being reported. Accredited veterinarians are required to report diseases listed in Appendix A and Appendix B of ATCP Chapter 10. Still, sadly, not everyone calls their veterinarian or reports when they have an issue.

Q: Based on the initial slide from DATCP: If we as veterinarians suspect an animal has a reportable disease, should we allow that animal to move from its current location, or how do we manage it regarding movement, testing, and reporting and what is the recommended timing of those actions?
A: No animal should be moved if there is ANY suspicion that it has a reportable disease (See Chapter 10 Appendices A & B). DATCP should be notified, and options should be discussed. The animal should be tested and ideally isolated from the other animals. An animal is prohibited from movement while awaiting test results (ATCP 10.18).
Also, see ATCP 10.08:
ATCP 10.08  Moving diseased animals.

(1)  GENERAL. No person may, in connection with the import, sale, movement, or exhibition of any animal, do any of the following:
(a) Knowingly conceal that the animal has been infected with or exposed to any contagious or infectious disease.
(b) Knowingly misrepresent that the animal has not been exposed to or infected with any contagious or infectious disease.
(c) Knowingly permit an animal that has been exposed to or infected with a contagious or infectious disease to commingle with other animals under conditions that may cause the disease to spread to an animal owned by another person.

Q: If the most recent case in Columbia County is unrelated to previous Wisconsin cases, do we know where it came from, and since it was at a sale facility, how many animals have been exposed and moved to new facilities prior to diagnosis, how complete is that tracing and are all of those facilities under quarantine or will be placed under quarantine?
A: We are investigating the Columbia County case and do not have these answers yet.

Q: How long do you typically treat with anti-viral medications?
A: If used (and it is typically financially dictated), they are most effective in the first week following exposure/infection— practically that means at the onset of observed fever. Their role is to reduce viremia, which will diminish the likelihood of neurologic disease—but this is most effective if the drugs are on board coincident with the high fever spike and perhaps the 2-3 days after that. By the time the horse has neuro disease their effectiveness is far less. For very valuable horses or clients willing to spend the money, we can continue valacyclovir to about day 10 (sometimes dropping dose frequency to twice daily and 20 mg/kg on days 7-10), but more often limit their use to the first 3-5 days of fever when cost curtails duration.

Q: Is it actually recommended to vaccinate for EHV four times annually?
A: We need to be careful which EHV, and what form of EHV you are talking about here—if you want to protect against abortion due to EHV-1 then a brood-mare should be vaccinated three times in gestation—at 5,7 and 9 months, specifically with a product that claims protection against abortion. With respect to EHV-1-associated respiratory disease—veterinarians should have a conversation with clients as to whether vaccination is appropriate given the risks and management/housing facility and use of the horse; and then realize that for effective protection, boosters every 90-120 days will be needed (these might be timed to coincide with higher risk periods—show season for example). A single EHV-1 vaccine given once a year for a horse with high risk will not be protective. Unfortunately, there is no vaccine protection against the neurologic form. EHV-4 is a slightly different herpes virus for which vaccines are available that is only associated with respiratory disease—the same comments/advice regarding EHV-1 and vaccinal protection versus respiratory disease really apply to EHV-4, too.

Q: How important is it to use virus transport media versus saline for recovery rates or accurate testing?
A: Sterile saline is acceptable if the WVDL can get the sample within 24 hours. All of the WVDL shipping UPS ground is overnight, anywhere in Wisconsin, for $12.50. The WVDL will receive the sample by 9 am. Do not send a sample that is dry. Remember not to use cotton or wood stick swabs because the bleach destroys nucleic acid. If you have any questions, call the WVDL at (608) 262-5432.

Q: A vaccine manufacturer has recommended a 3rd booster with Rhino vaccine. Would you agree with this recommendation in most horses?
A: The WVDL has not seen any published data that supports this claim. This should be a question for the veterinarian to make a plan for each horse based on exposure risk, age, and other health conditions.