Equine Infectious Anaemia
Learn what the condition is, how it may be detected early, how it is treated or managed, and which breeds or species are linked to it.
Condition snapshot
A concise guide to the condition’s pattern, detection, management and urgency.
Limit spread while seeking adviceSeparate affected animals when practical and obtain veterinary guidance on contacts, cleaning and normal mixing.
This snapshot is a general guide, not a diagnosis or treatment plan. New, severe or worsening signs require veterinary assessment.
About the condition
Equine infectious anaemia, or EIA, is a lifelong blood-borne lentivirus infection of horses, ponies, donkeys and mules. Virus is transferred mechanically when large biting flies carry infected blood between nearby equids. It also spreads through reused needles, syringes, intravenous sets, blood-contaminated dental or surgical equipment and untested blood products. It is not known to infect people.
Clinical expression ranges from no visible illness to recurring fever, depression, weakness, weight loss and reduced performance. During active episodes, platelet numbers can fall and red cells are destroyed or production is suppressed, causing petechiae, nosebleeds, pale or yellow mucous membranes, anaemia and dependent swelling of the legs or abdomen. Rare acute cases collapse and die. Many infected horses eventually appear normal but retain integrated virus for life.
Periods without fever do not mean the infection has cleared. Viral load fluctuates, rising during febrile episodes, and an inapparent carrier remains a potential source for flies or blood-contaminated procedures. No vaccine or curative antiviral treatment is available. This biology is why EIA testing is required for horse movement in many countries and why a confirmed result has permanent consequences.
Signs alone cannot distinguish EIA from piroplasmosis, immune-mediated blood disease, purpura or other causes of fever and anaemia. Geographic prevalence and regulations differ, but internationally EIA is controlled as a listed disease. Prevention depends on identifying carriers, using one sterile needle and fluid set per horse, testing blood donors and reducing blood-feeding insects rather than relying on clinical appearance.
Equine infectious anaemia virus persists for life in blood cells. Biting flies and contaminated needles transfer infected blood; transmission is not eliminated when fever subsides. Horses may suffer recurrent fever, thrombocytopenia, anaemia, oedema and weight loss or remain inapparent reservoirs. Stress or immune suppression can increase viraemia, so outward health cannot establish freedom from infection.
Screening & Early Detection
Screening uses serology for antibody to EIA virus. The agar gel immunodiffusion test, commonly called the Coggins test, is the internationally recognised confirmatory method. Approved ELISAs provide faster screening but reactive results require official confirmation. Tests can be negative early after infection before antibodies develop, so recent exposure may require quarantine and repeat sampling at the interval directed by authorities.
Testing frequency follows law, travel, competition, breeding and local risk. New arrivals should have documented current negative status or remain separated while testing is resolved. Blood donors require rigorous repeated screening. A febrile horse with anaemia, low platelets, jaundice or oedema is isolated from blood-sharing risks and reported promptly for diagnostic testing.
Positive results are handled through the regulatory process, including confirmatory samples and identification of exposed equids. PCR is not the routine carrier test because low virus levels and genetic variability can reduce sensitivity. A normal blood count does not exclude infection. Owners should verify certificates rather than relying on a seller’s verbal history, especially for imported horses or animals moved through high-prevalence regions.
Treatment & Management
There is no treatment that eliminates EIA virus. A confirmed horse remains infected for life, regardless of health or later absence of fever. Management options are dictated by jurisdiction and generally consist of humane euthanasia or permanent, officially supervised isolation at a prescribed distance from other equids with stringent vector protection. Moving or privately rehoming a positive horse is not an acceptable cure or control measure.
Supportive treatment might temporarily relieve anaemia or fever, but it does not remove the reservoir and can expose other horses through blood, equipment or flies. Regulatory veterinarians direct identification, movement restrictions, contact testing and any retesting. Needles, syringes, intravenous tubing and multidose-vial practices are reviewed immediately; blood-contaminated instruments are cleaned and disinfected correctly, and donors or products are traced.
Prevention includes current negative tests for incoming horses, sterile single-use injection equipment, approved blood products and effective biting-fly management. Open wounds are covered where practical, and equipment capable of carrying blood is never shared without validated decontamination. During a confirmed incident, testing schedules and release decisions come from animal-health authorities. There is no vaccine, supplement or insecticide programme that makes a known carrier safe to mix with uninfected equids.
Breeds or species affected
Akhal-Teke
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Anglo-Arabian
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Arabian
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Barb
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Caspian
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Kathiawari
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Marwari
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Shagya Arabian
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Thoroughbred
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American Quarter Horse
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American Paint Horse
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Appaloosa
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Australian Stock Horse
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Brumby
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Waler
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Morgan
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Standardbred
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American Saddlebred
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Tennessee Walking Horse
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Missouri Fox Trotter
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Rocky Mountain Horse
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Peruvian Paso
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Criollo
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Mustang
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Canadian Horse
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Andalusian
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Lusitano
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Lipizzaner
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Friesian
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Dutch Warmblood
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Hanoverian
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Holsteiner
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Oldenburg
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Westphalian
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Trakehner
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Selle Français
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Belgian Warmblood
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Danish Warmblood
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Swedish Warmblood
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Swiss Warmblood
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Australian Warmblood
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Irish Sport Horse
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Cleveland Bay
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Württemberger
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Zangersheide
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Knabstrupper
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Orlov Trotter
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Camargue
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Icelandic Horse
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Pony of the Americas
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Quarter Pony
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Miniature Horse
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Clydesdale
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Shire
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Percheron
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Belgian Draft
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Suffolk Punch
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American Cream Draft
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Ardennes
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Breton
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Boulonnais
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Comtois
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Dutch Draft
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North Swedish Horse
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Norwegian Fjord
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Haflinger
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Gypsy Cob
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Irish Draught
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Welsh Pony and Cob
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Connemara Pony
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New Forest Pony
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Dartmoor Pony
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Exmoor Pony
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Shetland Pony
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Highland Pony
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Fell Pony
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Dales Pony
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Australian Pony
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Finnhorse
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Black Forest Horse
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