Equine Protozoal Myeloencephalitis in Donkeys: EPM Signs, Testing & Treatment
- Equine protozoal myeloencephalitis, or EPM, is a neurologic disease of equids caused most often by *Sarcocystis neurona* and less commonly by *Neospora hughesi*. Donkeys are equids, so your vet may use horse-based evidence and dosing references when EPM is suspected.
- Common signs include asymmetric weakness, stumbling, incoordination, toe dragging, muscle wasting, head tilt, facial nerve changes, and behavior or vision changes. Signs can be subtle at first and may worsen over days to weeks.
- Diagnosis usually combines a neurologic exam, ruling out other causes of neurologic disease, and blood plus cerebrospinal fluid testing. A positive blood test alone does not confirm EPM because many equids have been exposed without becoming sick.
- Treatment options often include ponazuril, diclazuril, or sulfadiazine-pyrimethamine, plus supportive care such as anti-inflammatory medication, vitamin E, safer footing, and activity restriction as directed by your vet.
- Typical US cost range in 2026 is about $700-$1,800 for a basic workup and first treatment course, and $2,000-$5,500+ if spinal tap, imaging, hospitalization, repeat exams, or prolonged therapy are needed.
What Is Equine Protozoal Myeloencephalitis in Donkeys?
Equine protozoal myeloencephalitis, usually called EPM, is an infection of the brain and spinal cord caused by protozoal parasites. In equids, the two recognized causes are Sarcocystis neurona and Neospora hughesi. Most published research is in horses, but donkeys are also equids, so your vet may apply the same diagnostic approach when a donkey shows compatible neurologic signs.
The disease can affect almost any part of the central nervous system. That is why signs can look very different from one donkey to another. One donkey may have mild stumbling and uneven hind-end weakness, while another may show muscle loss, facial asymmetry, head tilt, or trouble standing.
EPM is important because it can mimic many other neurologic problems. A donkey with EPM is not always feverish or obviously painful, which can make the condition easy to miss early on. Prompt veterinary evaluation matters, because earlier treatment may improve the chance of stabilizing or improving neurologic function.
Even with treatment, recovery can be incomplete. Some equids improve enough to return to comfortable pasture life or light work, while others are left with lasting deficits. That makes realistic goal-setting with your vet an important part of care.
Symptoms of Equine Protozoal Myeloencephalitis in Donkeys
- Mild to marked incoordination or stumbling, often worse on turns or slopes
- Asymmetric weakness in one or more limbs
- Toe dragging, scuffing, or abnormal hoof wear
- Regional muscle wasting, especially over the hindquarters, shoulder, or face
- Uneven gait that may look like lameness at first
- Difficulty backing, crossing limbs, or standing squarely
- Head tilt or facial droop
- Abnormal sweating patches or reduced skin sensation in some areas
- Behavior change, dullness, or depression
- Vision problems, seizures, or trouble swallowing in severe brain involvement
- Recumbency or inability to rise in advanced cases
Watch closely for asymmetry. EPM often causes one-sided or uneven neurologic deficits rather than perfectly balanced weakness. Early signs may be subtle, such as a donkey that starts tripping more often, drifts to one side, or loses topline and hindquarter muscle on one side.
See your vet promptly if your donkey has new stumbling, weakness, muscle wasting, cranial nerve changes, or any sudden decline in balance. See your vet immediately if your donkey cannot stand normally, is falling, has seizures, cannot swallow, or seems unsafe to handle.
What Causes Equine Protozoal Myeloencephalitis in Donkeys?
In North America, EPM is most often linked to Sarcocystis neurona. Equids become infected after ingesting infective sporocysts in feed or water contaminated by opossum feces. Opossums are the recognized definitive host for S. neurona in the United States.
A smaller number of cases are associated with Neospora hughesi. The natural host cycle for N. hughesi is still not fully defined, which means prevention advice is less specific for that organism. In both infections, the parasite can spread and damage the central nervous system, leading to neurologic signs.
Exposure does not always mean disease. In horses, many animals have antibodies showing exposure, but only a small percentage develop clinical EPM. That is one reason your vet cannot diagnose EPM from a blood test alone.
Stress, transport, concurrent illness, and other factors that affect immune function may play a role in whether an exposed equid develops clinical disease. For donkeys, species-specific data are limited, so your vet will usually interpret risk factors in the context of the individual animal, local wildlife exposure, and the neurologic exam.
How Is Equine Protozoal Myeloencephalitis in Donkeys Diagnosed?
Diagnosis starts with a full history and neurologic exam. Your vet will look for patterns such as asymmetric ataxia, weakness, muscle atrophy, cranial nerve deficits, and whether the signs fit a brain, spinal cord, or multifocal problem. Because EPM can resemble trauma, cervical spinal cord disease, rabies, equine herpesvirus myeloencephalopathy, toxicities, and other conditions, ruling out alternatives is a major part of the workup.
Testing often includes serum and cerebrospinal fluid, or CSF, antibody testing. Cornell notes that a positive serum result mainly shows exposure, not definite disease. CSF testing is more helpful, especially when interpreted with the neurologic exam and with attention to whether blood contamination could create a false-positive result.
In practice, your vet may recommend a tiered plan. A more conservative workup may include farm exam, gait and neurologic assessment, and bloodwork before starting treatment if the suspicion is high. A more complete workup may add CSF collection, infectious disease testing, cervical radiographs, referral evaluation, or advanced imaging when available.
Response to treatment can support the diagnosis, but it should not replace a thoughtful workup. Repeating antibody tests over and over is usually less useful than tracking whether your donkey is actually improving on exam and in daily function.
Treatment Options for Equine Protozoal Myeloencephalitis in Donkeys
Spectrum of Care means you have options. Here are treatment tiers at different price points.
Budget-Conscious Care
- Farm call or haul-in exam with neurologic assessment
- Basic bloodwork and targeted rule-outs based on your vet's exam
- Empiric first-line antiprotozoal treatment when suspicion is high
- Usually one FDA-approved horse medication used extra-label in a donkey, such as ponazuril or diclazuril, with donkey dosing determined by your vet
- Short course of anti-inflammatory medication if your vet feels it is appropriate
- Vitamin E supplementation, safer footing, reduced work, and close home monitoring
Recommended Standard Treatment
- Comprehensive neurologic exam plus CBC and chemistry panel
- Serum and CSF EPM testing when feasible, often with other infectious disease rule-outs
- One full treatment course with ponazuril paste for 28 days, diclazuril pellets for 28 days, or sulfadiazine-pyrimethamine for at least 90 days, selected by your vet
- Supportive care such as NSAIDs early in treatment, vitamin E, stall or paddock rest, and rehab guidance
- One or more recheck exams to document gait, strength, and safety improvement
Advanced / Critical Care
- Referral hospital evaluation or intensive field management for severe neurologic disease
- CSF collection, broader infectious disease testing, cervical imaging, and additional diagnostics to rule out other spinal cord or brain disorders
- Hospitalization for donkeys that are unsafe to transport, falling, recumbent, or unable to eat and drink normally
- Extended or combination antiprotozoal therapy if response is incomplete, as directed by your vet
- Advanced supportive care including IV fluids, sling or assisted standing support, pressure sore prevention, nutritional support, and structured rehabilitation
Cost estimates as of 2026-03. Actual costs vary by location, clinic, and individual case.
Questions to Ask Your Vet About Equine Protozoal Myeloencephalitis in Donkeys
Bring these questions to your vet appointment to get the most out of your visit.
- You can ask your vet, "How strongly do my donkey's exam findings fit EPM versus other neurologic diseases?"
- You can ask your vet, "Would serum testing alone be misleading in this case, and do you recommend a spinal tap for CSF testing?"
- You can ask your vet, "Which antiprotozoal medication makes the most sense for my donkey, and why?"
- You can ask your vet, "What side effects should I watch for with ponazuril, diclazuril, or sulfadiazine-pyrimethamine?"
- You can ask your vet, "How will we measure improvement over the next 2 to 8 weeks?"
- You can ask your vet, "Does my donkey need stall rest, hand-walking, turnout restriction, or footing changes during recovery?"
- You can ask your vet, "What signs would mean this is becoming an emergency or that treatment is not working?"
- You can ask your vet, "What is the expected total cost range for the diagnostic plan and the first full treatment course?"
How to Prevent Equine Protozoal Myeloencephalitis in Donkeys
There is no proven vaccine for EPM. An older conditionally approved vaccine is no longer offered, so prevention focuses on reducing exposure and catching neurologic disease early.
The most practical step is to limit access of opossums to feed and water areas. Store grain and supplements in sealed containers, do not leave pet food out overnight, clean up spilled feed, remove fallen fruit, and manage garbage so wildlife is not attracted to the barn or dry lot.
Bird feeders near equid housing can also attract wildlife and increase contamination around feeding areas. If opossums are common on your property, ask your vet or local extension resources about safe, legal wildlife deterrence in your area.
Some clinicians discuss preventive antiprotozoal use in selected high-risk situations, but evidence-based prevention protocols are not firmly established. For most donkey herds, the best plan is environmental control, good general health support, and prompt veterinary evaluation of any new stumbling, weakness, or muscle loss.