How to Tell if Your Horse has EIA

Three Parts:Checking for SymptomsCaring for a Horse with EIAPreventing EIA

Equine Infectious Anemia (EIA), also known as Swamp Fever, is a viral equine disease that is very contagious between horses, persists throughout the entire life of its victims, and can be fatal. Though the Coggins test does check horses' blood for the disease and there may be a second vaccine on the way (see note), there are no known cures[1].

The virus has three stages: The acute stage, chronic (or subacute) stage, and carrier (or unapparent) stage. The acute stage is the most dangerous and claims up to 30% of its victims' lives[2].

Though one can't do much once a horse has been infected, one can check their horse for symptoms of the acute and chronic stage (the carrier stage has no symptoms) to ensure the health of neighboring horses.

Note: The Chinese have used their 'Chinese Live Attenuated EIA vaccine' on horses since 1983 for preventing infection of EIA[3], and there is another vaccine underway in the US[4]. However, many health organizations do not accept either vaccine nor trust them as effective.


  1. 1
  2. 2
    Learn the stages:
    • Acute: This is a full onslaught of the disease and kills up to 30% of its victims[5]. If your horse has this but makes it past the first 14 days since infection he should be okay.
    • Chronic: Chronic EIA horses go through the same severity of acute EIA horses but seem to recover after a few weeks. The symptoms then go away for weeks or even months until the horse has a relapse of worsened intensity, usually as result of being worked hard. Chronic EIA horses also can have rough hair coats, lack stamina, and be anemic[6].
    • Carrier: Carriers of the EIA virus will seem to completely recover from the initial attack, yet still carry and can transmit the disease.[7]

Part 1
Checking for Symptoms

  1. Image titled Take a Horse's Temperature Step 3
    Take your horse's temperature. A healthy adult horse's temperature while resting varies from to 99-101°F (37.2 - 38.3°C), while fever associated with EIA can range from 105-108°F (40.5 - 42.2°C).
    • The fever of an EIA-infected horse can either be highly intermittent or continuous[8]. It may help to take your horse's temperature several times throughout the day.
  2. 2
    Check the heartbeat for irregularity. This can be checked by placing the hand under the horse's left elbow. Count the beats for 10 seconds then multiply the beats by 6 to get the heartbeat number per minute. A normal heart rate is 35-40 beats per minute.
    • Irregularity may be a sign of infection with EIA.
  3. 3
    Offer your horse food near his usual eating time and observe him. A healthy horse likes his food and while eat it nearly as soon as you offer it. A horse that refuses food or has a reduced appetite, however, may have EIA.
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    Weigh your horse to see if he's been losing weight recently. Don't be concerned unless there has been no change of diet and your horse has had rapid or chronic weight loss.
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    Exercise the horse and see if he is unusually lethargic, depressed, or weak. Tiredness and depression are also signs of EIA.
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    Check the chest, stomach, and legs for abnormal swelling. Swelling is another sign of the horse having EIA.
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    Research horse diseases with similar symptoms and see if any match your horse's symptoms better or as well as EIA. Similar diseases include Piroplasmosis, African Horse Sickness, Anthrax, Dourine, Equine Viral Arteritis, Japanese Encephalitis, Equine Influenza, Equine Herpes Virus, and Babesiosis[9].
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    Contact your vet if your horse has you worried. He should be able to give you advice and confirm your horse's symptoms.
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    Coggins test your horse. This test is fairly inexpensive and only requires a certified vet sending a sample of your horse's blood to a lab. Usually the process takes 3-5 days.
    • A negative Coggins/EIA test result means your horse is not a carrier of the disease. If your horse continues having symptoms, tell your vet; your horse may be sick with something else.
    • A positive Coggins/EIA test result means your horse is an EIA carrier. If you feel the test was a false positive you can ask your vet to retake the Coggins, though you will need to pay for the test again.

Part 2
Caring for a Horse with EIA

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    Realize that having a horse with EIA is a major threat to neighboring horses' lives, and there are no cures for the disease[10].
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    Advise horse owners within exposure area to have their horses Coggins tested. This will reduce the potential of EIA spreading throughout the area.
    • Some areas say area of exposure is within proximity of 200 yards (180 meters) of the infected horse, other areas say within proximity of 3 miles (4.8 kilometers)[11].
  3. 3
    Decide what to do with your EIA-infected horse. Legally you only have three choices: Keeping your horse at a quarantine facility for the rest of its life, having the horse euthanized, or selling the horse for immediate slaughter[12].
    • There aren't many quarantine facilities, but one of the largest ones, Florida Research Institute for Equine Nurturing, Development and Safety, is located in Southern Florida[13].

Part 3
Preventing EIA

  1. 1
    Reduce fly numbers around the barn. Large-mouthed flies such as deer-flies and horseflies will quickly spread the EIA virus by mechanically sharing an infected horse's blood with other horses.
    • Regularly clean and muck stalls/pens around the barn, depositing the manure a good distance away.
    • Eliminate any standing water; flies use these as breeding grounds.
    • Use fly-repelling sprays and fly traps around the barn.
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    Keep a horse's bridle bit to itself. Infected mouth germs will share the EIA disease just like blood.
  3. 3
    Use disposable needles when giving your horse shots or drawing blood. This will prevent an infected horse's blood from getting into other horses.
  4. 4
    Sterilize any surgical equipment and similar instruments. While this is a good practice anyway, the threat of EIA makes it an even better one.
  5. 5
    Keep your horse happy. While diseases can definitely be fatal, a horse is much less prone to becoming sick if he's happy and well cared for.


  • EIA is less commonly known as Mountain Fever, Slow Fever, Equine Malarial Fever, and Coggins Disease.[14]

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