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EHV-1 Outbreak in Minnesota

EHV-1 Outbreak in Minnesota affects barrel horses

EHV-1, or equine herpesvirus 1, is currently a hot topic here in Minnesota. In March 2014, several horses in Minnesota and western Wisconsin have shown neurologic signs of the disease, and some have been euthanized.  This outbreak of the disease has roots in the barrel racing scene, at a competition in Winona, MN in early March.  Cases have appeared in Hennepin, Chisago, Dakota, and Wright County in MN, as well as Burnett and Polk County in WI. Information is still emerging, but several of the horses who have been euthanized have connections to the barrel horse world. 

On Wednesday, March 26, the University of Minnesota Equine Center hosted a free seminar and Q&A session on EHV-1 presented by Dr. Carrie Finno and Dr. Christine Ward. It was well attended with at least 50 people at the Nutrena Conference Center and over 200 attendees online.  The talk went on for about two hours, and covered everything from the history of the disease to how to properly disinfect and quarantine horses who are displaying neurologic symptoms. “We need to respect this disease,” Dr. Finno told the group. That was one of the most memorable takeaways – respecting the severity of EHV-1 and containing it is our responsibility as horse owners and professionals. 

EHV-1 facts to know

In the talk, veterinarians from the University outlined several key facts to keep in mind about EHV-1. These include:

  • EHV-1 has 4 clinical presentations:
1) Neurological disease – also known as equine              herpesvirus myoencephalopathy (EHM) 
--Neuropathic (N-type) 
--Non-neuropathic (D-type)
2) Respiratory disease
3) Neonatal death
4) Abortion in pregnant mares
  • Both the N & D type can cause neurologic symptoms 
  • Like human influenza, EHV-1 has a “season,” typically during spring and fall
  • EHV-1 is highly contagious, and spreads by:
1) Horse-to-horse contact
2) Contact with physical objects contaminated with the         virus (brushes, buckets, stall walls, people’s hands and     clothing)
3) Inhalation

What are “neurologic symptoms”?

According to Dr. Finno, when EHV-1 progresses to EHM (the neurological form of the disease), there are several symptoms you could notice in your horse.  If your horse is displaying any of these symptoms, call your veterinarian immediately:

  • Hind-end weakness, or “puppy sitting”
  • Incoordination – may appear “drunk” and stumbling
  • Urine dribbling in mares, or inability to contract penis in geldings or stallions
  • Inability to stand

Before any of these symptoms appear, horses almost always have a fever, respiratory disease, coughing, and/or thick nasal discharge. Fevers may spike in horses 4-6 days after exposure – though incubation periods as short as 24 hours can occur. 7-12 days after a fever, these neurological symptoms typically present.  

How do I know if my horse has EHV-1 or EHM?

Surprisingly, many horses carry EHV-1 in a latent state and live healthy lives without ever showing signs of the disease.  According to some studies cited by Dr. Finno, 63-75% of horses carry EHV-1 in their systems, and up to 30% of horses already have antibodies that can defend them against it (i.e. these horses have been exposed at some point to it and their immune systems fought it off). “We don’t recommend taking nasal swabs on horses that don’t have symptoms and haven’t been exposed,” Finno told attendees – because in the end, horses can be positive for EHV-1 and not need treatment.

EHM can develop in times of stress, when EHV-1 becomes active. Horses with compromised immune systems, especially older horses and pregnant mares, can be the most susceptible. Stressful events can include competitions, races, and shows.  

Dr. Finno stressed in her talk that proper testing of animals showing signs of the disease is crucial. Both nasal swab testing and blood testing are used to determine the stage of the virus. 

Can it be treated?

“It is incredibly treatable, but you've got to recognize it, and you've got to get on top of it early,” Finno told the group. Both Dr. Finno and Dr. Ward stressed that getting the horse isolated and off the property is the best course of action if severe neurological symptoms are present. If a horse is affected by the neurological strain, antiviral drugs can help with  recovery in some cases. Having access to a sling and other supportive nursing care can also speed the healing of a horse with EHM – a clinic setting with around-the-clock care is ideal. 

If horses do not have severe neurological symptoms but are testing positive for EHV-1, the University recommends isolating them from other horses and treating with anti-inflammatory drugs and other supportive care methods. Regular veterinary care, regular flu/rhino boosters every six months, and management of stress can all aid your horse’s immune system when faced with disease. 
What is “biosecurity,” and why is it needed?

Biosecurity measures can help keep this EHV-1 outbreak contained. In general, the best biosecurity is simply limiting the movement of horses until the outbreak is contained, and preventing exposed horses from interacting with herd mates. Both Dr. Finno and Dr. Ward confirmed that it may not be a good time to trailer over to a heated arena, go to a clinic, or to attend an event for a few weeks. In addition, quarantining new arrivals to your barn and any horses that have been to an event where EHV-1 has been confirmed present is paramount. 

People are carriers, too – touching noses of infected horses or handling feed and water buckets can spread the disease. Handwashing, disinfecting equipment, and changing clothing and footwear before going to a different barn can help contain the spread of EHV-1. Footbaths may also be effective against the spread of EHV-1 on the bottom of boots.

What do veterinarians recommend?

Right now, the University of Minnesota veterinarians are warning horse owners to limit transport of horses between facilities, and to quarantine any horses showing signs of the disease. Horses showing neurologic symptoms shed millions of copies of the disease, which can pass to other horses, people, equipment, and even the air around them.  

The handout Dr. Finno provided the group (available on the University of MN Equine Center facebook page) outlined protocol for horses returning from events where EHV-1 cases have been confirmed. These precautions include:

  1. Isolation from any other horses at the stable
  2. Checking rectal temperatures 2x/day – contact your vet if the temp is 102 or above
  3. Observing closely for neurologic signs, respiratory disease, and fevers for 3 weeks post-event
  4. Clean all equipment with dilute bleach or other common disinfectants (a great tutorial is available from The Horse website
  5. If you’re handling affected horses, change clothes, footwear, and gloves and/or consider showering before handling other horses
  6. If a horse shows acute neurologic symptoms, moving the animal to a biosecure facility with a sling can help with recovery

If there is no confirmed case of EHV-1 at an event your horses have been to recently, the University still recommends monitoring for fever and symptoms for at least 2 weeks after the event.
How is Animal Connections helping?

As an equine health professional and a horse owner, Dr. Kyla is taking extra precautions during this outbreak to help keep horses safe. She’ll be changing clothes and shoes between visits, washing her hands between treatment of horses, disinfecting her blocks, as well as limiting the number of barns visited per day until the outbreak has been contained.  

For further information and resources, the handout from Dr. Finno’s talk is available by visiting the University of Minnesota Equine Center’s facebook page.

4 Comments to EHV-1 Outbreak in Minnesota:

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Janee Dehler on Sunday, March 30, 2014 10:12 AM
Do we know if the horses who have presented the symptoms of EHV or EHM were previously vaccinated?
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Animal Connections on Sunday, March 30, 2014 10:43 PM
Hi Janeee, I don't think that information is readily available at this time. There is more on this EHV-1 outbreak available at the University of MN Equine Center's facebook page. There are a few links in this post you can use to get there.
Reply to comment

Denice Porterfield on Wednesday, April 9, 2014 1:37 AM
I live just a few miles from the most resent confirmed case of EHV-1. I have 3 horses. We rarely leave the property with them. Is there any chance of my horses being exposed to this virus? Such as from insects or such? Do I need to worry?
Reply to comment
Animal Conenctions on Wednesday, April 9, 2014 10:45 AM
Hi Denise - I'm not sure about insect transmission - but there are a bunch of great resources for you in a later blog post: In general, if you have concerns, it's important to reach out to your veterinarian for the most current recommendations and precautions.

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