Urgent Notice: Equine Clients

Written by Administrator on . Posted in RVVS Blog

Attention Horse Owners: 4/3/14 EHV1 Update from Dr. Viren:

As of 4/3/14 there are nine confirmed positive cases.

  • 3/8/14 Chisago County (MN) 2 horses, 1 was euthanized
  • 3/18/14 Dakota County (MN) 1 horse euthanized
  • 3/20/14 Polk County (WI) 1 horse
  • 3/21/14 Hennepin County (MN) 1 horse
  • (Pending) Burnett (WI) 1 horse euthanized
  • 3/26/14 Freeborn County (MN) 1 horse
  • 3/26/14 Iowa - traveled in from Freeborn and Hennepin Counties
  • to the Cedar Rapids area 1 horse
  • 4/3/14 Wright County (MN) 1 horse


Currently the equine veterinary community is requesting that horses NOT be transported unless absolutely necessary. Hopefully, in a week or two we will have a better understanding of what is happening with the EHV1 situation and return to our normal equine activities. The best way to stop the virus is to practice strict biosecurity measures and to not stress our horses with travel. Biosecurity is the process of taking measures to protect humans and animals from diseases or harmful biologic agents. Biosecurity means doing everything you can to reduce the chance of an infectious disease being carried from farm to farm by people, animals, equipment or vehicles. Isolation and quarantine measures are very effective in stopping the EHV1 virus.

If anyone has questions about the EHV1 outbreak, please call Dr. Viren and he will be happy to answer your questions. Also, feel free to post questions here and we will do our best to get you answers. Here are some facts about EHV1:

  • EHV1 virus is a normal occurring virus found in the equine population. In other words, the large majority of the world wide horse population has been exposed and carry the virus in a latent form (dormant state). An estimated 20% of these horses carry the mutant form of EHV1 (G2254/D752) that causes myeloencephalopathy (neurologic disease).
  • The current cases are confirmed to be the non-neuropathogenic strain. This is a good thing because the neuropathogenic strain (G2254/D752) is particularly nasty, producing 10 to 100 times more viral shedding, making it extremely contagious and infectious.
  • The current cases are the non-neuropathogenic strain (A2254/N752) and yet some of these cases had to be euthanized because of neurologic signs. This current strain has proven that it can still produce neurologic disease in some individual horses. The reason that the non-neuropathogenic strain of EHV1 causes neurologic signs in some horses is not understood. Researchers are still trying to understand the factors that determine why both of these strains cause varying clinical signs.
  • The EHV1 virus can survive in the environment for up to 30 days in perfect conditions, but usually survives only 7 days. The virus does not like dry environments. The virus likes wet and cold environments.
  • The most simple way to monitor your horse for EHV1 is by taking the temperature twice a day. Make sure to keep a written log of the temperatures.
  • The veterinary community does not know why EHV1 re-activates in some horses, thus causing clinical disease. Perhaps stress is a primary cause such as travel and showing that suppresses the immune system. These same EHV1 latent viruses can be traced back to the 1950's with the same genetic "fingerprint". There are also possible epigenetic factors that influence the expression of the virus. The re-activation of the EHV1 virus is similar to herpes simplex or shingles in humans.
  • In 2007, EHV1 neuropathogenic strain was classified as a reportable disease (the state and feds became involved). The reason is because the neuropathogenic strain of EHV1 is classified as an emerging disease (becoming more common).
  • No vaccine is licensed to prevent neurologic disease. However, current EHV1 vaccines are effective at stimulating high titers of virus neutralizing antibody that bind infectious viral particles. This will reduce the amount and length of time of virus shedding. The goal is to reduce the total viral numbers in a group of horses.

Dr. Viren believes that vaccination will help achieve that goal. Please remember that vaccination is no substitute for enforcement of strict biosecurity measures, At RVVS we have been vaccinating hoses that travel and show frequently with an EHV1 specific product since 2006.