The ~Texas~ Mustang Project's Blog

Working for better management options and cohabitation through compromise and communication for the American Wild Mustang

Equine Infectious Anemia Information from Utah, Re: Winter Ridge HA

Posted by Texas Mustang Project on August 9, 2010

As promised, the information below is in reference to the Equine infectious anemia disease occurrences within the Winter Ridge Herd Area. This information and the map below are from Mr. Gus Warr, Wild Horse & Burro Specialist / Utah Program Lead, BLM-Utah State Office.

I did try to reach the Ouray National Wildlife Refuge today, but to no avail. I left messages so hopefully someone in their office will call back to explain why their NWR’s horses are not being managed. The information I received today stated basically that because the wild horses were no longer a “cash crop” as they were once upon a time to the Ouray Indian Reservation that they’ve pretty much been left to their own devices. This lack of management has allowed them to travel across HA and HMA boundaries, as well as into the neighboring towns and pastures, thus infecting domesticated horses as well with EIA. They are infected with the EIA antibodies because – again – of a lack of management of both their herds and their habitats.

But before we go any further, here’s a little history and info about EIA itself:

The equine infectious anemia virus in horses is similar to the HIV virus in humans. Both the EIA virus and HIV are capable of producing their own DNA. The DNA then attaches itself to the cells within the body and begins to replicate. Once the cells of the virus have begun to reproduce, they begin to take over the normal cell structures of a horse’s body. Over time, this can lead to the systematic failure of all organs and an extremely depreciated immune system.

EIA is mainly carried by mosquitos and biting flies. While no, there are not near the amounts of mosquitos in the Northwestern part of the US  as there are in my neck of the woods, there are still a great deal of them when their numbers are left unchecked. For instance, we spray continually to keep down their breeding in order to make it “ok” just to walk outside and not get hit with a B-52 Bomber Mosquito. (I’m not joking… They really are big enough that when they land, you actually feel them on your skin!)

When EIA is left unchecked as well, you have a recipe for the perfect breeding ground: mosquitos breed and populate -> find “food” on the unchecked populations of wild horses -> one or two that have EIA -> find more food on other horses = a whole population of horses with EIA!

For those of you who have never seen what EIA does to a horse, count yourself lucky. For those of you who have been unfortunate enough to see the awful ravages of this disease on an Equine’s body and systems, I am so sorry. It is heart wrenching to see, let alone to deal with on an emotional level if the Equine is your own.

By the way: not all horses who are infected with EIA antibodies exhibit signs or symptoms. There are some horses who will never show any effects of the disease. However, because the Equine infectious anemia virus (EIAV) is categorized as a retrovirus, it contains genetic RNA material, which it uses to produce DNA. This DNA is then incorporated into the genetic makeup of infected cells.

It is often difficult to differentiate from other fever-producing diseases, including anthrax, influenza, and equine encephalitis. In the acute form of the disease the horse usually dies within days of the onset of contracting the virus. The horse runs a high fever (104 -108 degrees), exhibits severe depression, loses his appetite, and his physical condition deteriorates rapidly. There are heavy concentrations of the virus in the animal’s bloodstream. A sub acute form is similar to the acute, but less severe. Most horses recover after a week or two and remain well for several weeks or months. They become weak and unthrifty and anemic, especially when under stress. Then the virus reappears, causing death. In the chronic form the horse has reoccurring bouts of illness following an acute or sub acute stage. They also have a high concentration of the virus in their bloodstream.

The inapparent carrier is the center of the disagreement over the laws concerning EIA. In this form the horse carries the virus in his bloodstream, but is not sick. The virus count is very low, which can be determined by a test called the SID test. In addition, the inapparent carrier shows no signs of illness, whereas the chronic horse is unthrifty, showing loss of fat, and muscle mass. The inapparent carrier does not have a fever. Owners of those horses have their temperatures monitored regularly.

It has been estimated that 85% to 90% of horses infected with EIAV, present as sub clinical infections without ever having shown observable clinical signs of the disease. Furthermore, many of these horses have long productive lives and survive long periods without febrile episodes being induced by EIAV in spite of their being AGID (Coggins test) positive. Many horse owners have their horses tested as per state laws with little understanding of what the test is for, or the consequences of their horse testing positive. Some even think the Coggins is a vaccination. According to a 1998 survey done by the USDA’s National Animal Health Monitoring System 30.3% of horse operations had never heard of EIA, 16.3% recognized the name, but not much else, and 22.5% knew some basics. Only 30.9% were really knowledgeable about EIA.

So if the horse can live full and productive lives without any problems, what’s the point in euthanizing the horse at all? Well, for most that answer is very clear: Because they are carriers, and because their disease is not always asymptomatic. Mosquitos that bite and infected horse and then bite a non-infected horse transmit the disease. The chance alone is enough to make even the most devoutly loving owner opt to euthanize his horse, that is, if he is in a state that will allow a choice. Most states, including my own – Texas – and the state of Utah will not allow the choice of euthanization or quarantine because the risk of further infection is simply too high.

Unfortunately, there is no immediate cure or vaccination available for this illness. While there are vaccinations that have been tested, they have not been found to be safe for use in horses; even stacked up against the odds of fatality caused by the equine infectious anemia virus. The best thing that horse owners can do is to try to eliminate the possibility of infection and reduce the spread of the infection when it is apparent. Regular and clean stable maintenance is a crucial aspect of keeping the transmission of this virus down. Keeping manure picked up and stalls clean will help reduce the amount of flies and mosquitoes circling around fresh manure; essentially decreasing the chances of an infected insect making contact with a horse.

SO! Now that you’ve got a somewhat muddy to clear idea of what this disease really is, here are the statistics promised! As an added “bonus” of sorts, please also see the attached pdf file from Tuscarora and how horses without a negative Coggins test were transported across state lines: UT State Vet Shipping OK – end 022811 


BLM / State of Utah / Uintah & Ouray Indian Reservation wild horse gather & EIA testing cooperative effort (see attached map below).

  • Bonanza East – 99 tested, 0 positive
  • East Bench (outside HA) & West Bonanza – 111 tested, 59 positive
  • Agency Draw – 51 tested, 0 positive
  • Tabyago – 172 tested, 0 positive


Bonanza HA gather – 216 captured & tested, 31 positive


Bonanza HA gather – 92 captured & tested, 0 positive (all wild horses located within the HA were removed).


Hill Creek HMA gather – 253 captured & tested, 6 positive


Hill Creek HMA & Winter Ridge HA gathers:

  • Hill Creek – 152 captured & tested, 0 positive
  • Winter Ridge – 41 captured & tested, 0 positive


Hill Creek HMA (Outside) – 16 captured, 2 positive

Map of 1998 BLM/State of Utah/Uintah & Ouray Indian Reservation Wild Horse Gathers & EIA Testing:

  • Bonanza East –  99 tested, 0 positive
  • East Bench (outside HA) & West Bonanza 111 tested, 59 positive
  • Agency Draw –  51 tested, 0 positive
  • Tabyago –  172 tested, 0 positive


4 Responses to “Equine Infectious Anemia Information from Utah, Re: Winter Ridge HA”

  1. reveil said

    Since they are wild, how do we know that they are carrying the virus?
    Wild horses are often blamed for diseases which originated with domesticated animals, such as sheep and cows. Wild horses are typically blamed for everything under the sun.

    • LOL well… when they are gathered and tested and those tests reveal positive results, that would mean that they are carrying the virus.
      No, it didn’t originate with the wild horse populations. It actually came from France – go figure… how’s that for irony!
      But anyway! The point is this: this is not about the blaming game on wild horses or domesticated horses. This is about the extreme lack of management occurring in this Herd Area and it’s surrounding areas. No, I’m not talking about BLM lack of management. As much as this leaves a nasty taste in my mouth to say, I gotta say what I know to be fact at this point in time: the lack of management is from the Ouray Indian Reservation. Just because the wild horses no longer make them a profit, they are no longer considered to be worth the time of day. The main focus now is on wildlife in the Ouray National Wildlife Refuge.

      • reveil said

        When it’s not due to the wild horses, blame it on France!
        I understand the issue here, but i think that the disease is endemic to the US, Europe, the Middle East, Russia, Africa, pretty much the entire globe.
        I think not long ago there was a study linking a virus to domesticated cattle. May be it had to do with bison, I don’t remember.

  2. Karl Jobst said

    Karl Jobst

    Equine Infectious Anemia Information from Utah, Re: Winter Ridge HA « The ~Texas~ Mustang Project’s Blog

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