By Terri Rocovich
Rocking Horse Ranch
I have a VERY serious subject to my blog today. As I am sure many of you have already heard, there has been a major outbreak of the EHV-1 in the western Unites States. EHV-1 is a strain of the Equine Herpes Virus that commonly affects horses around the world. There are actually 5 strains of the Equine Herpes Virus but the most common are EHV-1 and EHV-4. Both of these strains generally manifest themselves as upper respiratory tract infections and/or can cause abortions in pregnant mares.
What is unusual about the recent outbreak of EHV-1 is the number of cases that have resulted in EHM - Equine Herpesvirus Myeloencephalopathy which is a neurologic mutation of the virus that affects the horse's brain and spinal cord and can lead to paralysis and death.
All of the current reported cases relate initially to a Cutting Horse Championship Show in Ogden, Utah that took place 4/29 - 5/8. The suspected first case exhibited neurologic signs at the show and was taken to a nearby equine hospital where it was later euthanized. So far all of the confirmed cases of EHM are in horses that attended the Utah show or a subsequent Cutting Horse Show in Bakersfield, California. No secondary or unrelated cases of EHM have been reported to date.
As of today, there are nearly 50 confirmed cases in 9 western states plus Canada. There are also over 20 unconfirmed cases. California is one of the hardest hit states with 18 confirmed cases in over 12 counties. Other States affected are Texas, Idaho, New Mexico, Oregon, Utah, Washington, Colorado, and Arizona.
Precautions to Take
EHV-1 is EXTREMELY contagious and can be spread by either direct or indirect contact (nasal secretions) or infected aerosolized droplets ( i.e. sneeze or cough). People can easily transmit the virus on our hands, shoes or clothing or it can live on other items like tack, grooming equipment, manure forks, buckets, feed tubs, water sources, or even the tires of your vehicle. Therefore good barn hygiene like frequently cleaning water buckets and feed tubs with a 10% bleach solution or other disinfectants like chlorhexidine and biosecurity measures such as not sharing or disinfecting brushes, tack or other commonly shared items. Infected or suspected horses should be isolated at least 60 feet away and extreme sterile protocol should be used when around that horse.
Horses can be latently infected, and potentially infect other horses without ever displaying symptoms themselves. Incubation period of EHV-1 is typically 1 to 14 days. EHM generally appears 8 - 12 days after primary infection. Horses can shed the virus for up to 21 days after they stop showing clinical signs. EHV-1 and EHM are designated as "reportable diseases" which means that a veterinarian is mandated to report any case to the state in which the case is identified and the horses must be quarantined.
Clinical Signs to watch our for.
Fever and/or a nasal discharge are usually the first signs of the disease. Fevers of 102 or greater are of concern and a vet should be consulted. Other clinical signs include: Inappetance, ataxia (stumbling/incoordination), paralysis, lower leg swelling, inability to urinate or pass manure, urine dribble (incontinence), reduced tail tone.
How to stop it.
Most vets agree that the best way to stop any virus is to simply stay at home limiting the mixture/exposure of horse populations. This is the approach I am taking with my facility. Even though no cases have in reported in San Diego county where my farm is and I don't have any clients or known horses near me that were at that Cutting Horse show, I have seen any number of diseases spread like wildfire over the years and no horse show is worth putting any of my horses at any degree of risk. Wisely, several shows in my area have already been cancelled but many others have not including a Rodeo with participants from all over the western U.S. that took place in my area this past weekend. As a result, I have placed my facility on a 21 day quarantine (no horses in or out) from today just in case it could have been brought into the area by horses co mingled at the rodeo. I may be cautious to the extreme, but to me it is worth the peace of mind and luckily all of my clients are in agreement.
There is no vaccine for EHM and vets are in disagreement as to whether horse owners should booster with the vaccines known to protect against EHV-1 and EHV-4. From what I have read it is important NOT to booster your horse if you suspect any level of exposure. For example, the weekend prior to the announcement of the EHV-1 outbreak, I had been at a Eventing Horse Trials with a few of my students of which one of the horses lives at my barn. After hearing of the outbreak the next day I chose to have my vet nasal swab this horse and send it to UC Davis to test for EHV-1 exposure. After getting a negative test result, we boostered every horse on my facility with Rhinomune a strong modified live vaccine (a killed vaccine like Pneumabort -K should be used on pregnant mares or breeding stock). A few of the horses had mild reactions (not uncommon) to the vaccine but everyone was back to normal within a day. My decision to vaccinate was based on the fact that boostering can reduce virus shedding within farm populations and enhance protection against EHV-1 even though it won't protect against the EHM neuropathogenic mutation.
Not to be taken lightly.
This is clearly a serious situation that every horse owner needs to pay attention to whether you show or not. Many horse owners today keep there horses at stables with large populations and any travel in/out while this outbreak is prevalent can put your horse at increased risk.
The most up to date information that I have been able to find is on the following web sites:
I hope that this danger passes by quickly and that every one's horses remain happy, healthy and sound!