Share On

Jump To

Jump To Section

Share On

Jump to
    Add a header to begin generating the table of contents

    Jump To

    Jump To Section

    Equine Infectious Anemia: Protecting Your Equine Residents

    A cartoon tan horses wearing a bridle stands in front of a grey fence while a veterinarian wearing a blue coat uses a stethoscope to check their heart rate. A person wearing a dark ball cap and green sweater holds the horses lead rope.
    vet review seal

    Veterinary Review Initiative
    This resource has been reviewed for accuracy and clarity by a qualified Doctor of Veterinary Medicine as of September 2023. Check out more information on our Veterinary Review Initiative here!

    Legal/Vet Advice/Reportable Diseases
    When it comes to diseases that may trigger reporting requirements to local, state, or federal governmental entities, we recommend that you consult both with your veterinarians and knowledgeable local legal counsel with regard to your obligations. It is important to be aware of the local requirements regarding reportable disease for all species for whom you care. Please keep in mind that The Open Sanctuary Project is neither staffed by veterinarians and is not a law firm. This resource is not a substitute for the services of either a veterinarian or an attorney. Accordingly, you should not construe any of the information presented as veterinary or legal advice. Please review our disclaimer if you haven’t yet!

    Equine infectious anemia, or EIA, is a blood-borne viral disease transmitted primarily through biting insects. You may have heard it referred to as “swamp fever” or “horse /equine malaria.” This is because swampy areas generally have higher populations of these insects, increasing the likelihood of infection. This disease affects equines all over the world, though it is fairly uncommon. All equines, including horses, mules, donkeys, and zebras, can be affected. While EIA isn’t incredibly common in the United States and some other countries, a positive test could result in serious, even fatal, consequences. Although an individual may survive the disease (albeit with a lifetime infection), some states and countries have mandatory euthanasia regulations. If you care for any equines at your sanctuary, it is important to understand your area’s risk level, the signs of disease, and, most importantly, how to prevent your residents from contracting it. This short resource will introduce you to the basics of the disease, how it is spread, prevention, symptoms of the disease, and vet care. We know protecting residents is your top priority, and this will help keep equine residents happy and healthy! Let’s get to it.

    Equine Infectious Anemia

    EIA is a bloodborne virus. It replicates in blood cells, circulating throughout the body and triggering the affected individual’s immune system. When this happens, their white blood cells produce antibodies to fight off the pathogen, and in doing so, the antibodies attack their blood cells. This destroys platelets and red blood cells and causes a lifelong infection within many organs and tissues. Sadly, there is no cure for EIA to date. Neither is there a vaccine currently approved to protect equines. 

    As mentioned above, any equine can be affected. This disease is spread primarily through biting insects, particularly horseflies, deer flies, and mosquitos. However, equine residents can also contract EIA through contaminated needles or other instruments. EIA can also be spread from mare to fetus, which is important if you are caring for a pregnant equine resident. If a resident is affected, the incubation period can take between a week to well over a month. If you live in a region with four seasons, late summer and early fall can be a time of particular risk due to an increase in insect activity. If you live in a typically warm and humid region, there is likely also an increased risk of resident equines contracting the disease. Wherever you live, it is vital you speak with an experienced veterinarian about the possible risk factors unique to your area. 

    Equine Infectious Anemia can affect individuals differently, ranging from acute transitory symptoms to chronic episodes of symptomatic illness. Let’s take a closer look at each of the three possible stages an infected equine may go through.

    Not A Zoonotic Disease

    While this is a terrible viral disease that can affect equine residents, there isn’t a risk of caregivers contracting the illness. However, caregivers should always take care and follow biosecurity measures, including using separate tools and equipment for the infected individuals. To be clear, this disease is generally transmitted through biting insects or unhygienic veterinary practices. Even so, while the chances of shared equipment infecting another resident equine is quite low, it isn’t worth the risk. There are diseases and parasites that can absolutely spread through shared tools.

    We recommend checking out our resource, Understanding Zoonotic Disease: An Overview For Animal Sanctuaries, for more information.

    Stages Of Equine Infectious Anemia

    There are three stages of illness an affected resident can experience. Below, we look briefly at each of these stages and how they may present in a resident. Any resident showing these symptoms should be isolated as soon as possible, and a veterinarian should be called for testing. In cases of diseases caused by biting insects, the further they are from another equine, the less likely an insect carrying contaminated blood is to bite and infect another resident. This can be stressful and upsetting for them and their herd mates. Moving them should be done carefully, with consideration to their mental and emotional well-being. For example, if they have visual access to their companion(s), this can be helpful at times.

    Acute Stage

    In an individual suffering from the initial acute case of EIA, the virus is actively replicating and attacking the immune system. There will generally be high levels of the virus in their blood, which can be verified through testing. (This is less true for donkeys and mules.) They may begin to show symptoms. These symptoms often last around 1-3 days. Symptoms can vary in severity, with some being fairly mild and possibly missed if they aren’t being adequately observed. It is vital for caregivers to develop an understanding of typical species’ behavior and the normal behavior of the individual for this reason. Symptoms may include:

    • Mild to high fever
    • Lethargy
    • Lack of appetite 
    • Anemia
    • Depression
    • Death (This is rare but possible)

    Once the acute phase has passed, they may become subclinical carriers or suffer from chronic episodes of the disease.

    Subclinical Carrier Stage

    A subclinical carrier is an individual who carries the virus but shows no obvious signs of illness. Basically, they could have it, and you wouldn’t know it. Unfortunately, the illness doesn’t have to be clinically observable for biting insects to pass the disease from the carrier to another equine resident. Stressors such as transport, loss of a companion, or other illnesses could cause an episode or recurrent episodes. Recurrent episodes indicate a chronic phase of the disease. 

    Donkeys And Mules

    There is evidence that donkeys, while susceptible to EIA, often do not exhibit clinical symptoms. This may be due to the low viral load of the disease in their blood compared to that of horses that have been infected. Similarly, mules appear to be less likely to develop severe symptoms, and infection may go unnoticed without close observation of residents. Both donkeys and mules, once infected, become carriers and, as with other equine species, must be separated from other equine residents following federal and state regulations (as described later in the resource).

    Chronic Stage

    If an individual is dealing with a chronic infection, they will experience times of remission and times of active illness. Stressors can trigger episodes of disease activity, and symptoms can vary in type and severity. Some of these symptoms can include:

    • Recurring fever
    • Increased heart rate
    • Increased respiratory rate
    • Anemia
    • Jaundice
    • Weakness
    • Depression
    • Low platelet levels (abnormal bleeding, inhibited clotting)
    • Petechiation on mucous membranes (red or purple spots caused by burst capillaries)
    • Nosebleeds
    • Swelling in the legs
    • Poor body condition
    • Poor coordination


    Unfortunately, there is no vaccination for EIA. Luckily, there are steps you can take to mitigate the risk and spread of EIA and protect your equine residents. To start, test new residents for EIA. In the United States, a Coggins test is the most common test (though there are others available in different countries) and must be administered by an accredited veterinarian and sent to an accredited laboratory testing facility. Part of prevention is following strict quarantine measures to protect other residents. Here is a list of steps you can take:

    1. Request proof of a recent negative Coggins test (we talk more about this below) before bringing new equine residents to sanctuary grounds.
    2. Have a qualified veterinarian perform a Coggins test before moving an equine resident to sanctuary grounds.
    3. Quarantine new equine residents for 45 days before introducing them to other residents.
    4. Practice proper manure management.
    5. Limit areas of standing water.
    6. Clean in and around living areas frequently and remove organic matter such as damp straw, and garbage.
    7. Use fly deterrents/repellents.
    8. Keep tall grasses trimmed down.
    9. Use disposable needles and syringes. Never use the same needle on multiple residents.
    10. Ensure only sterile veterinary tools are used on residents.
    11. Do not use the same nasogastric tube for multiple residents.

    Testing And Diagnosis

    In the United States, the test for EIA is referred to as a Coggins test, named after veterinarian Leroy Coggins, who first developed it. Each state has its own regulations surrounding Coggins testing. Be sure to speak with your veterinarian about Coggins (and other) testing that may be required and the appropriate steps to take when bringing in a new equine resident. Many states require annual testing and proof of testing. If you move across state lines, you will need to provide proof of a negative Coggins test in the past 12 months or even more recent in some states.

    If you live in another country, especially one where temperatures are conducive to high biting insect populations, speak with your veterinarian about the necessary regulations to follow.

    Record Keeping Is Vital!
    One of the most important things that you can do for each of your residents may not be the most entertaining or glamorous job, but consistent record keeping kept in a safe, well-organized location is critical for resident health and safety, as well as the safety and success of your sanctuary. Each resident should have their own permanent record. Among other things, you will need to have a certificate from each Coggins test for every equine resident.

    We recommend always asking your veterinarian for a copy of all diagnostic results so that you can include them in your residents’ records. It’s also important to include information about why the diagnostic test was performed (was this a routine screening test, or was the individual showing signs of concern?) and to take thorough notes about your veterinarian’s interpretation of diagnostic results.

    Check out the following resources for more on recordkeeping:

    How To Create, Maintain, And Organize Permanent Records For Your Residents
    The Importance Of Regular Health Documentation For Animal Sanctuary Residents

    If They Test Positive

    Because there are strict regulations regarding EIA, in the event a resident tests positive, there are steps that must be taken and difficult decisions to make. An equine who tests positive cannot be adopted out or moved from the sanctuary but must be permanently quarantined and isolated from other equines (unless they are also EIA+) or, sadly, euthanized. (Under federal regulations, they can legally be transported with a special permit to be sold to testing facilities and to slaughter, but we consider this unacceptable.) If the infected individual is to be quarantined, they must live 200 yards away from any other equines. This is because the range of biting insects carrying the disease is smaller than 200 yards.

    At The Open Sanctuary Project, unacceptable means that we cannot condone (or condone through omission) a certain practice, standard, or policy. See a more detailed explanation here.

    Depending on where you live, procedures and regulations will vary. Be sure to find out what is required in your country/state. In review, if someone tests positive for EIA in the United States, the federal regulatory options are:

    • Permanent quarantine
    • Euthanasia
    • Sell and transport to slaughter (Unacceptable)
    • Sell and transport to an approved research facility (Unacceptable)

    Each state has its own regulations that must be followed, and we highly recommend contacting your state veterinarian when EIA is diagnosed. Your state veterinarian will know the most current recommendations for state and federal requirements. This means all of the options above may not be approved by your state. In fact, a few states sadly require mandatory euthanasia as part of their attempt to prevent disease spread. Below, we will briefly cover permanent quarantine and euthanasia. As previously stated, we feel the other options are unacceptable. Let’s talk more about quarantine first.

    Compulsory Euthanasia In Some Countries And States

    While most states allow for EIA-positive equines to live out their lives in permanent quarantine, 200 yards away from any other equine species, some states and countries enforce compulsory euthanasia.


    In the United States, if an equine resident tests positive for EIA, they must be separated and quarantined within 24 hours of receiving the positive test results. They must be quarantined at least 200 yards away from other equine residents. If the resident will be staying in permanent quarantine, then they will be required to have permanent identification in the form of a National Uniform Code number tattooed or branded on their person. Methods of identification approved by the USDA include hot iron branding, chemical branding, freeze marking, and lip tattooing. This mark must be applied by an accredited veterinarian or APHIS representative. There are rules as to the placement and size of these markings as well. Speak with a compassionate veterinarian about the least painful method and what they can do to ease any pain or discomfort that might be caused during the placement of the permanent marking.

    Transport of the individual is generally limited to transporting them back to the sanctuary if they were offsite when testing positive. Special permitting is often required for this trip, and you will be required to obtain a special certificate in order to care for the resident in quarantine permanently. The area in which the individual will live must be approved by regulatory officials.

    If permanent quarantine is the chosen course, it is especially important the resident has a dynamic living environment and an enrichment schedule to help meet their needs and ensure an interesting and (otherwise) healthy life.


    This is partly a philosophy of care decision and can depend on the factors at play. If the individual is severely affected by EIA and has a poor quality of life, euthanasia may be a compassionate choice. You should always advocate for your residents. However, if you live in certain states or countries, euthanasia may be government-mandated, and you may not have a choice at all.

    Other challenges may arise as well. You may find yourself in the predicament of simply not having enough space to adhere to the 200-yard separation requirement intended to protect other residents from contracting the disease. And while we do not condone euthanasia due to space constraints, the government will likely require it if you are unable to meet the stipulations. This is something to consider for your sanctuary contingency plans. Discuss ahead of time what you could do if such a situation happened. How would you go about handling it? How can you prevent it?

    Discussing euthanasia is never easy. If you are faced with a decision you are uncomfortable with, don’t make the decision alone. Speak with your veterinarian and care staff, advocate for your resident, and determine if there are any possible options to provide a quality life for the individual while protecting others and meeting the regulations of your government.

    Other Residents

    If one resident tests positive, all other equine residents must be tested as well. They must stay in place and be considered under quarantine until it is evident they are all free of EIA. No new residents should be introduced at this time. They will need to be tested again 30-60 days after the initial positive test. Once everyone has tested negative for at least 60 days, they can be considered out of quarantine.


    If there are equines on a neighboring property, you will want to alert them so they can have their horses tested. Additionally, you will have to ensure you can house the resident at least 200 yards from any neighboring equines as well as those on sanctuary grounds.

    Regulations May Vary
    Regulations may vary between countries and between states and local governments. It is imperative that you learn about the regulations in your area. You can start by reaching out to your local veterinarian for region-specific information.

    Now that we have covered some of the basics of this disease, it’s a good time to speak with your veterinarian about any questions you may have. Knowing the risk factors in your area and following biosecurity protocols can go a long way in protecting your equine residents from contracting this and other blood-borne viral diseases.


    Viral Diseases That Affect Donkeys And Mules | Animals (Non-Compassionate Source)

    Equine Infectious Anemia (EIA) | University Of Tennessee Institute Of Agriculture (Non-Compassionate Source)

    Understanding Equine Infectious Anemia (EIA) | Alberta Veterinary Medical Association (Non-Compassionate Source)

    Equine Infectious Anemia | The Merck Veterinary Manual (Non-Compassionate Source)

    Equine Infectious Anemia | The Center For Food Security And Public Health (Non-Compassionate Source)

    Equine Infectious Anemia | UC Davis Veterinary Medicine (Non-Compassionate Source)

    Equine Infectious Anemia: The Only Protection Is Prevention | American Association Of Equine Practitioners (Non-Compassionate Source)

    Equine Infectious Anemia: Uniform Methods and Rules | USDA (Non-Compassionate Source)

    Economic And Geographic Impact Of Equine Infectious Anemia In Louisiana | LSU College Of Agriculture (Non-Compassionate Source)

    Seroprevalence And Risk Factors Associated With Equine Infectious Anemia In The State Of Goiás, Brazil | Preventative Veterinary Medicine (Non-Compassionate Source)

    Communicable Diseases In Horses, Asses, Ponies, Mules, And Zebras | Animal and Plant Health Inspection Service, USDA (Non-Compassionate Source)

    Non-Compassionate Source?
    If a source includes the (Non-Compassionate Source) tag, it means that we do not endorse that particular source’s views about animals, even if some of their insights are valuable from a care perspective. See a more detailed explanation here.

    Article Tags

    About Author

    Get Updates In Your Inbox

    Join our mailing list to receive the latest resources from The Open Sanctuary Project!

    Continue Reading

    Skip to content