Equine Infectious Anemia in Donkeys: Swamp Fever Signs and Testing
- See your vet immediately if your donkey has fever, weakness, swelling, weight loss, or unexplained anemia and has had exposure to other equids or biting flies.
- Equine infectious anemia, also called swamp fever, is a lifelong viral infection of equids including donkeys. There is no cure and no vaccine.
- Some donkeys may have mild or no obvious signs, so routine blood testing is important even when an animal looks well.
- Diagnosis is made with USDA-approved blood tests such as AGID, commonly called the Coggins test, and approved ELISA screening tests.
- A positive donkey is a lifelong carrier and state or federal control rules apply, including permanent isolation or euthanasia depending on the case and local regulations.
What Is Equine Infectious Anemia in Donkeys?
Equine infectious anemia, or EIA, is a viral disease of equids caused by a lentivirus. Donkeys, horses, mules, and zebras can all be infected. You may also hear it called swamp fever. The virus lives in the blood, and once a donkey is infected, it remains infected for life.
This disease matters because some donkeys become very sick, while others look normal but still carry the virus. Clinical signs can come and go, especially during flare-ups. That means a donkey can seem stable for a period of time and then develop fever, anemia, weakness, or swelling later.
EIA is also a reportable disease in the United States. There is no approved treatment that clears the infection and no vaccine to prevent it. Because infected donkeys can spread the virus to other equids, your vet and animal health officials may need to guide testing, movement restrictions, and long-term management.
Symptoms of Equine Infectious Anemia in Donkeys
- Recurring fever
- Anemia or pale gums
- Depression or lethargy
- Weight loss or poor body condition
- Swelling of the legs or underside of the body
- Weakness or exercise intolerance
- Small pinpoint hemorrhages or low platelets
- No visible signs at all
See your vet immediately if your donkey has fever, weakness, swelling, collapse, or signs of anemia. EIA can look like several other serious conditions, so it cannot be confirmed by symptoms alone.
It is also important to worry when a donkey seems normal but needs a health certificate, interstate travel paperwork, herd screening, pre-purchase testing, or has had contact with a positive equid. Donkeys may show subtle signs, and routine testing often finds infection before obvious illness appears.
What Causes Equine Infectious Anemia in Donkeys?
EIA is caused by the equine infectious anemia virus, a blood-borne virus spread mainly when infected blood moves from one equid to another. The classic route is through biting flies, especially horseflies and deer flies, which can mechanically transfer blood between nearby animals.
The virus can also spread through human-related blood contamination. Examples include reused needles, syringes, IV equipment, contaminated multidose medication vials, and unscreened blood products or transfusions. This is called iatrogenic transmission, and it is preventable with careful hygiene and biosecurity.
A donkey does not need to look sick to spread EIA. Animals that survive infection become lifelong carriers. Stress, illness, or heavy work may trigger flare-ups with higher virus levels in the blood, which can increase transmission risk.
How Is Equine Infectious Anemia in Donkeys Diagnosed?
Your vet diagnoses EIA with a blood test, not by symptoms alone. The best-known test is the AGID test, commonly called the Coggins test. USDA-approved laboratories also use approved ELISA tests for screening. If a screening test is positive, confirmatory testing is typically required under regulatory protocols.
Timing matters. After a new infection, it may take 60 days or more for an equid to test positive, and some sources note that early infections can be missed before antibodies are detectable. If exposure is recent but the first test is negative, your vet may recommend repeat testing and temporary separation from other equids.
Diagnosis often includes more than the lab result. Your vet may also perform a physical exam, complete blood count, and review travel history, herd exposure, fly pressure, and any recent injections or transfusions. Because EIA is reportable, positive results trigger official follow-up and movement restrictions.
Treatment Options for Equine Infectious Anemia in Donkeys
Spectrum of Care means you have options. Here are treatment tiers at different price points.
Budget-Conscious Care
- Farm call and exam
- USDA-approved EIA blood testing
- Immediate separation at least about 200 yards from other equids while results or official instructions are pending
- Basic supportive care directed by your vet for fever, dehydration, or weakness
- Strict single-use needles and blood-handling biosecurity
- Fly control and environmental management
Recommended Standard Treatment
- Full veterinary exam and herd risk assessment
- USDA-approved EIA testing with any needed confirmatory testing
- CBC and chemistry panel to assess anemia, platelets, hydration, and organ status
- Supportive care plan tailored by your vet
- Written quarantine and fly-control plan for the property
- Coordination with state animal health officials on legal next steps
Advanced / Critical Care
- Emergency stabilization for severe weakness, dehydration, or collapse
- Hospitalization or intensive on-farm monitoring when available
- Serial bloodwork and close reassessment
- IV fluids or other supportive measures as directed by your vet
- Consultation with internal medicine or equine specialists when needed
- Detailed planning for long-term isolation, welfare, or humane end-of-life decisions
Cost estimates as of 2026-03. Actual costs vary by location, clinic, and individual case.
Questions to Ask Your Vet About Equine Infectious Anemia in Donkeys
Bring these questions to your vet appointment to get the most out of your visit.
- Which EIA test are you recommending for my donkey right now, and does it need confirmatory testing?
- If this first test is negative, when should we repeat it based on the most recent possible exposure?
- What other diseases could look similar to EIA in a donkey with fever, anemia, or swelling?
- How far should I separate this donkey from other equids on my property while we wait for results?
- What fly-control steps matter most for my barn, pasture, and water areas?
- Do any recent injections, dental work, blood products, or shared equipment increase concern for blood-borne spread?
- If the test is positive, what are my legal options in this state for isolation, quarantine, or euthanasia?
- Which other donkeys, horses, or mules on the property should be tested now?
How to Prevent Equine Infectious Anemia in Donkeys
Prevention focuses on testing, fly control, and blood safety. Ask your vet about routine EIA testing for every donkey on the property, especially before travel, shows, sales, breeding moves, rescue intake, or mixing with new equids. USDA and Merck sources support regular testing, and many situations require a current negative test for movement.
Good biosecurity also matters. Never reuse needles, syringes, or IV sets between animals. Blood transfusions and blood products should only be handled by your vet using properly screened donors and approved products. Avoid sharing anything that could carry fresh blood.
If you bring in a new donkey, keep it separated until your vet reviews testing status and movement paperwork. Reduce biting fly exposure with manure management, drainage, fans where appropriate, physical barriers, and targeted fly-control products your vet recommends. If EIA is suspected, move the donkey away from other equids right away and call your vet immediately.