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Equine Infectious Anemia & Coggins Tests

Equine Infectious Anemia (EIA), also known as “swamp fever,” is a disease that threatens the world’s horse, donkey, and mule populations.  More than 500 new cases are identified each year in the United States and there is no cure for this federally reportable disease.  While most infected horses show no outward symptoms, they remain contagious for life and endanger the health of other horses.  Due to this fact, horses testing positive must be euthanized or under strict lifelong quarantine.


Equine Infectious Anemia virus reproduces in white blood cells that circulate throughout the body.  A horse’s immune system may attack and destroy red blood cells leading to anemia.  Inflammation associated with viral infection may result in damage vital organs (bone marrow, liver, heart, and kidney).  Secondary infections may occur due to subsequent immunosupression.


Equine Infectious Anemia is transmitted by blood or passage across the placenta directly to the foal.  Blood transmission can occur via bloodsucking insects (horse flies, deer flies, mosquitoes), blood transfusion, or by blood-contaminated needles and instruments.


Equine Infectious Anemia may be difficult to diagnose because the clinical signs are non-specific.  Clinical signs of EIA may include one or more of the following:

   • Fever

   • Depression

   • Small hemorrhages on mucous


   • Swelling of legs, lower chest, abdomen


   • Decreased appetite

   • Fatigue, reduced stamina, weakness

   • Rapid breathing

   • Sweating

   • Rapid weight loss

   • Nasal bleeding (epistaxis)

   • Colic

   • Abortion

   • Irregular heartbeat and/or weak pulse


The only accurate way to determine whether a horse is infected with EIA is by identifying antibodies in the blood.  The Coggins test, an agar gel immunodiffusion (AGID), is considered to be the “gold standard.”

   • A negative Coggins test means there are no detectable antibodies at the time of testing.

   • A positive Coggins test indicates the horse is infected and is a carrier of the virus


There are management and geographic factors that increase the risk of a horse contracting EIA:

   • Close proximity to where EIA outbreaks have been identified

   • Steady influx of new horses (especially if negative Coggins tests are NOT required)

   • Exposure to horses at shows, sales, or events

   • Pasturing in swampy areas and areas where all horses are not regularly tested for EIA


There is no effective treatment for Equine Infectious Anemia.  There is no vaccine to prevent it and there is no cure.  However, good management can reduce the potential of infection.

   • Test all horses for EIA at least annually

   • Test horses at the time of purchase examination

   • Require current negative Coggins certificate for all horses entering premises

   • Quarantine new horses for 45 days and observe for any signs of illness before introducing

     them into the herd

   • Keep all stable areas clean, dry, and waste-free

   • Remove manure from pasture and provide adequate drainage to discourage breeding

     sites for pests

   • Horses at greater risk should be tested more frequently (every 4-6 months)


If your horses tests positive for Equine Infectious Anemia, the options you have are extremely limited due to the fact that it is a federally reportable disease.  Euthanasia is recommended as the most prudent, albeit emotionally difficult, option.  Alternatively, EIA positive horses are required by law to be permanently identified via branding or tattooing and quarantined for life in a screened stall.


Stopping the spread of Equine Infectious Anemia is everyone’s responsibility.  Owner compliance with EIA testing has aided in a significant decline in cases of the last 20 years.  By having your horse tested, you will be doing yourself, your animal, and the entire equine industry a favor.  The cost is minimal and the price is well worth the peace of mind.

Education | Equine Infectious Anemia & Coggins Tests

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