Why Is My Horse Wobbly? Neurological Signs, EPM, Wobblers and EHV
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Why Is My Horse Wobbly? Neurological Signs, EPM, Wobblers and EHV
By Dr Duncan Houston
A practical guide to recognising neurological problems in horses, knowing what is urgent, and understanding why the diagnosis is not always obvious.
A wobbly horse is never something to brush off.
Sometimes the cause is mild, slowly developing and manageable. Other times, weakness, stumbling, dragging toes, muscle loss, head tilt, difficulty swallowing or urine dribbling can point to a serious neurological disease affecting the brain, spinal cord or nerves.
The hard part is that many neurological diseases in horses can look similar at first. EPM, Wobblers, EHV, West Nile virus, botulism, trauma, rabies risk, Hendra virus in relevant Australian regions and even severe lameness can all create signs that owners describe as “off behind” or “not quite right.”
The safest approach is simple: do not guess from one sign. Look at the pattern, check for fever, keep the horse safe, and involve your veterinarian early.
Quick Answer
A horse that is wobbly, weak, stumbling, dragging toes, losing muscle, tilting the head, struggling to swallow, dribbling urine or unable to stand may have a neurological problem. Common causes include Equine Protozoal Myeloencephalitis, known as EPM, cervical vertebral compressive myelopathy, commonly called Wobblers, and the neurologic form of equine herpesvirus, called EHM. EPM is mainly linked to opossum feces contamination in the Americas, Wobblers involves spinal cord compression in the neck, and EHM is a contagious EHV-1 emergency that requires immediate isolation. (Cornell Vet College)
Call a veterinarian urgently if the signs are sudden, worsening, associated with fever, affecting swallowing or urination, causing collapse, or if more than one horse is affected.
What Counts as a Neurological Sign in a Horse?
Neurological signs happen when the brain, spinal cord, cranial nerves, peripheral nerves or neuromuscular system are not working normally.
Owners may notice:
• Stumbling
• Toe dragging
• Hindlimb weakness
• Wobbliness or ataxia
• Crossing limbs
• Difficulty turning
• Falling or nearly falling
• Muscle wasting
• Facial droop
• Drooping lip, eyelid or ear
• Head tilt
• Abnormal eye movement
• Difficulty swallowing
• Feed or water coming from the nostrils
• Urine dribbling
• Loss of tail tone
• Behaviour change
• Seizures
• Recumbency or inability to rise
The first clinical question is not “which disease is it?” The first question is: is this horse safe and does this need urgent veterinary care?
A mildly uneven horse that has been the same for weeks is different from a horse that became weak, febrile and unable to urinate overnight.
Neurological Risk Framework for Horses
| Risk level | What it looks like | What it may mean | What to do |
|---|---|---|---|
| Low risk | Subtle poor performance, mild stumbling, no fever, no worsening, horse is bright and safe | Early lameness, mild weakness, pain, poor conditioning or subtle neurologic disease possible | Book a veterinary exam if it persists, worsens or affects ridden work |
| Moderate risk | Repeated stumbling, toe dragging, mild ataxia, muscle loss, head tilt, mild facial asymmetry | Neurologic disease becomes more likely | Arrange a veterinary examination and avoid hard work |
| High risk | Clear wobbliness, weakness, difficulty turning, falling, difficulty swallowing, urine dribbling, rapid muscle loss | Serious neurologic disease, spinal cord compression, EPM, EHV, WNV, botulism or trauma possible | Call your veterinarian urgently and keep the horse safe |
| Critical | Unable to rise, severe ataxia, seizures, severe weakness, fever with neurologic signs, multiple horses affected, respiratory distress, sudden collapse | Emergency neurologic, infectious, toxic or traumatic disease possible | Isolate if infectious disease is possible and seek urgent veterinary care immediately |
The key decision point: a wobbly horse with fever, urine dribbling, difficulty swallowing, collapse or multiple affected horses is an emergency until proven otherwise.
EPM in Horses
EPM stands for Equine Protozoal Myeloencephalitis.
It is a neurological disease of horses caused mainly by Sarcocystis neurona and less commonly by Neospora hughesi. Horses are typically exposed to S. neurona by ingesting feed, hay, pasture or water contaminated with opossum feces. Horses are dead-end hosts, meaning they do not spread EPM directly to other horses. (Cornell Vet College)
What EPM usually looks like
EPM can affect different parts of the nervous system, so signs can vary. The classic clue is asymmetry, meaning one side or one region is affected more than the other.
Common EPM signs include:
• Asymmetric ataxia
• One-sided weakness
• Focal muscle wasting
• Toe dragging
• Strange or inconsistent lameness
• Facial droop
• Head tilt
• Difficulty swallowing
• Reduced sensation
• Behaviour changes in some cases
The major trap with EPM is testing. A positive blood test usually means exposure, not active disease. Cornell notes that CSF testing with paired serum is more predictive of active disease than serum alone, and AAEP guidance states that positive serum testing does not confirm central nervous system infection. (Cornell Vet College)
Why EPM is often overdiagnosed
Many healthy horses in the United States have been exposed to the organisms linked with EPM, but only a small percentage develop clinical disease. This means a positive blood test in a horse with vague lameness can be misleading. The diagnosis should be based on the neurological exam, the pattern of signs, ruling out other diseases, and appropriate serum plus CSF interpretation where needed. (Cornell Vet College)
In practice, the mistake I see most often is treating the blood test instead of diagnosing the horse.
Wobblers in Horses
Wobblers is the common name for cervical vertebral compressive myelopathy or cervical vertebral stenotic myelopathy.
This is a condition where the spinal cord is compressed in the neck. It can occur in young, growing horses because of developmental abnormalities, or in older horses due to degenerative changes, arthritis or narrowing around the spinal cord. UC Davis describes CVCM as spinal cord compression in the neck that can cause incoordination and weakness, with treatment depending on lesion type, severity, duration of signs and age. (Center for Equine Health)
What Wobblers usually looks like
Wobblers commonly causes:
• Symmetrical or fairly even ataxia
• Hindlimb wobbliness
• Stumbling
• Toe dragging
• Poor body awareness
• Weakness that may be worse behind
• Difficulty backing up
• Trouble turning tightly
• Knuckling or abnormal limb placement
• Neck pain or stiffness in some horses
A useful comparison is that EPM often looks more asymmetric, while Wobblers often looks more symmetric. That is not perfect, but it is a helpful starting point.
How Wobblers is diagnosed
Diagnosis may involve:
• Neurological examination
• Cervical radiographs
• Myelography in selected cases
• CT in referral settings
• Ruling out EPM, EHV, trauma and other neurologic diseases
This is not a condition to diagnose from a video alone. A horse that looks like a Wobbler may have EPM, EHV, trauma, West Nile virus, botulism, severe lameness or another spinal cord disease.
Equine Herpesvirus and EHM
Equine herpesvirus, especially EHV-1, can cause respiratory disease, abortion, neonatal disease and the neurologic form called equine herpesvirus myeloencephalopathy, or EHM. EHV spreads through nasal secretions, respiratory droplets, contaminated hands, clothing, tack, buckets, stalls, trailers and aborted fetal material. (AAEP)
What EHM usually looks like
EHM can cause:
• Fever before neurologic signs
• Hindlimb weakness
• Wobbliness or ataxia
• Urine dribbling
• Urine retention
• Loss of tail tone
• Difficulty rising
• Recumbency
• Rapid worsening
This is where urgency changes dramatically.
EPM does not spread horse to horse. Wobblers is not contagious. EHV can spread through a property.
A horse with fever plus weakness, wobbliness or urine dribbling should be isolated immediately and assessed by a veterinarian. EDCC states there is currently no vaccine labelled to prevent the neurologic form of EHV-1, so vaccination does not remove the need for isolation, testing and biosecurity. (Equine Disease Communication Center)
EPM vs Wobblers vs EHV: Quick Comparison
| Feature | EPM | Wobblers | EHV neurologic form, EHM |
|---|---|---|---|
| Main cause | Protozoal infection affecting the nervous system | Spinal cord compression in the neck | EHV-1 infection affecting blood vessels in the nervous system |
| Contagious between horses | No | No | Yes, EHV-1 is contagious |
| Typical pattern | Often asymmetric | Often more symmetric | Fever first, then neurologic signs in some cases |
| Common signs | One-sided weakness, muscle loss, facial signs, ataxia | Wobbliness, stumbling, poor body awareness, neck-related spinal signs | Fever, hindlimb weakness, urine dribbling, ataxia, recumbency |
| Key diagnostic issue | Blood tests show exposure, not necessarily disease | Requires neurologic exam and cervical imaging | Requires isolation and PCR testing when suspected |
| Urgency | Urgent if worsening or severe | Urgent if unsafe, worsening or traumatic | Emergency if fever or neurologic signs appear |
This table helps, but it does not replace an exam. Neurological cases are full of overlap. The pattern points the vet in the right direction. It does not make the diagnosis by itself.
Other Neurological Diseases That Can Look Similar
EPM, Wobblers and EHV are important, but they are not the only causes of neurological signs in horses.
West Nile virus
West Nile virus is a mosquito-borne viral disease that can cause ataxia, muscle twitching, weakness, behavioural change, paralysis, recumbency and death. AAEP reports that horses showing clinical West Nile signs have an approximate case fatality rate of 33%, and about 40% of survivors may have residual gait or behavioural abnormalities six months later. Vaccination is recommended as a core vaccine for horses in North America. (AAEP)
Rabies
Rabies is rare in many managed horse populations, but it is fatal and zoonotic where present. Horses may show agitation, aggression, colic-like behaviour, difficulty swallowing, paralysis, drooling, abnormal gait or rapid progression to death. People can be exposed when handling the mouth or saliva of an infected horse. (MSD Veterinary Manual)
Botulism
Botulism causes progressive flaccid weakness. Horses may show weak muscle tone, difficulty swallowing, drooling, tremors, inability to stand for more than a few minutes, laboured breathing and recumbency. It can be rapidly fatal without aggressive treatment. (MSD Veterinary Manual)
Hendra virus in relevant Australian regions
In Australia, especially regions where Hendra virus is a concern, fever with respiratory or neurological signs should trigger immediate veterinary caution. NSW Health states that Hendra virus can cause rapid onset illness in horses with fever, increased heart rate, rapid deterioration and respiratory and/or neurological signs, and that infection can occasionally pass from horses to people after close contact. Queensland Government states that vaccination of horses is the most effective way to help manage Hendra virus disease. (NSW Health)
Trauma and spinal injury
Falls, flips, paddock accidents, kicks, fence injuries or casting episodes can injure the neck, back, pelvis or spinal cord. Sudden weakness after trauma should never be assumed to be EPM.
Severe lameness that mimics neurologic disease
A painful horse can look neurologic. Severe foot pain, pelvic injury, stifle pain, laminitis, hoof abscess, cellulitis or fracture can all make a horse stumble, resist movement or look weak behind.
This is why a good vet does both: a neurological exam and a lameness-aware assessment.
When Is This an Emergency?
Call a veterinarian immediately if your horse has:
• Sudden wobbliness
• Rapidly worsening ataxia
• Fever with weakness or wobbliness
• Urine dribbling or inability to urinate
• Difficulty swallowing
• Feed or water coming from the nostrils
• Head tilt with severe imbalance
• Facial paralysis
• Recumbency or inability to rise
• Seizures
• Severe depression
• Collapse
• Respiratory distress
• Sudden neurologic signs after trauma
• Multiple horses affected
• A horse in a Hendra risk region with fever, respiratory signs or neurologic signs
If EHV, Hendra virus, rabies or another infectious disease is possible, do not move the horse through the property and do not allow normal horse-to-horse contact while waiting.
What Should You Do Right Now?
1. Stop riding and keep the horse safe
Do not lunge, ride, chase or force a neurologic horse to keep moving.
Place the horse somewhere:
• Quiet
• Non-slip
• Free from sharp objects
• Away from other horses if infection is possible
• Easy for the vet to access
• Safe for handlers
A wobbly horse can fall suddenly. Handler safety matters.
2. Check the temperature
A fever changes the urgency and the disease list.
A fever with neurologic signs makes EHV, West Nile virus, Hendra virus in relevant regions, systemic infection and other urgent causes more concerning.
3. Look for infection clues
Check for:
• Nasal discharge
• Cough
• Recent travel
• Recent show or clinic attendance
• New arrivals on the property
• Other sick horses
• Abortion in mares
• Mosquito exposure
• Wildlife exposure
• Opossum contamination risk in EPM regions
• Hendra risk region and flying fox exposure in Australia
4. Record what you see
Take short, safe videos if the horse can be observed without risk.
Useful views include:
• Walking straight away and toward you
• Turning left and right
• Backing up if safe
• Head and face symmetry
• Tail tone and urine dribbling
• Any muscle loss
Do not put yourself in danger to get video. A safe video helps. A kicked owner does not.
5. Call your veterinarian
Tell them:
• When signs started
• Whether signs are worsening
• Temperature
• Whether the horse is eating
• Whether the horse can swallow
• Whether the horse can urinate
• Whether the horse can stand
• Recent travel or exposure
• Other horses affected
• Vaccination history
• Any trauma history
• Your region and disease risks
6. Do not medicate blindly
Do not give leftover anti-inflammatories, antibiotics, sedatives or human medication without veterinary advice.
Medication can mask fever, change the exam, complicate infectious disease response or make a weak horse less safe.
How Vets Diagnose Neurological Problems in Horses
A proper workup usually starts with localisation. Your vet is trying to work out where the nervous system is affected.
The process may include:
• Full physical examination
• Temperature, heart rate and respiratory rate
• Neurological examination
• Cranial nerve assessment
• Gait assessment
• Tail tone and anal tone assessment
• Muscle symmetry assessment
• Lameness examination where needed
• Bloodwork
• Infectious disease testing
• Serum and CSF testing for EPM where appropriate
• PCR testing for EHV where appropriate
• Cervical radiographs or advanced imaging for Wobblers
• Ultrasound, radiographs, CT or myelography in selected cases
• Referral for advanced diagnostics in severe or unclear cases
The point is not to run every test on every horse. The point is to avoid jumping to the wrong disease because one sign seems familiar.
Common Mistakes Owners Make With Neurological Signs
Mistake 1: Assuming every wobbly horse has EPM
EPM is important, but Wobblers, EHV, West Nile virus, botulism, trauma, rabies risk, Hendra virus in relevant regions and lameness can all look similar.
Mistake 2: Trusting a blood test without the clinical picture
With EPM, blood tests can show exposure, not active disease. A positive test does not automatically explain the signs. (Cornell Vet College)
Mistake 3: Missing fever
Fever is one of the biggest clues that the case may be infectious or urgent. EHV can begin with fever before obvious neurologic signs. (AAEP)
Mistake 4: Keeping the horse in work
A neurologic horse can fall, injure itself or injure the rider. Stop ridden work until the horse is assessed.
Mistake 5: Ignoring urine dribbling
Urine dribbling or bladder dysfunction is a major red flag, especially with EHM.
Mistake 6: Waiting because the horse is “only a little wobbly”
Mild signs can still progress. A small neurological sign deserves proper attention, especially if it is new.
Mistake 7: Forgetting herd risk
If multiple horses are affected, think infectious, toxic or environmental until proven otherwise. EPM does not spread directly between horses, but EHV and some other conditions can involve multiple horses.
How To Reduce Neurological Disease Risk
You cannot prevent every neurological problem, but you can reduce several major risks.
Practical prevention includes:
• Keep core vaccines current where recommended, including rabies and West Nile virus in relevant regions
• Keep EHV vaccination current based on travel, competition and breeding risk
• Understand that EHV vaccination does not prevent EHM completely
• Use strict biosecurity at shows and after travel
• Quarantine new and returning horses
• Avoid shared buckets and gear at events
• Reduce mosquito breeding areas for West Nile virus prevention
• Store feed securely in EPM regions to reduce opossum feces contamination
• Keep hay and grain away from wildlife access
• Avoid feeding spoiled haylage or contaminated feed that may increase botulism risk
• Vaccinate for Hendra virus in relevant Australian regions after veterinary advice
• Check horses daily for gait, appetite, behaviour and temperature changes
• Treat trauma, falls and neck/back injuries seriously
Prevention is not about one disease. It is about reducing the number of ways the nervous system can get into trouble.
Myth vs Reality
| Myth | Reality |
|---|---|
| “A positive EPM blood test means EPM.” | It usually means exposure. Diagnosis needs clinical signs and better testing where possible. |
| “Wobblers only affects young horses.” | Young horses are classic, but degenerative cervical disease can also affect older horses. |
| “Vaccinated horses cannot get neurologic EHV.” | No vaccine is labelled to prevent EHM completely. |
| “If the horse is still standing, it can wait.” | Some neurologic diseases progress quickly, especially with fever, swallowing issues or urine dribbling. |
| “Neurologic signs always mean brain disease.” | Spinal cord disease, nerve disease, muscle weakness, toxins and severe lameness can all look neurologic. |
| “Only one affected horse means it is not infectious.” | Early outbreaks often start with one horse. Fever and exposure history matter. |
Frequently Asked Questions
How do I tell EPM from Wobblers?
EPM often causes asymmetric signs such as one-sided weakness, focal muscle loss or facial nerve changes. Wobblers often causes more symmetrical incoordination from spinal cord compression in the neck. This pattern helps, but it is not enough to diagnose either disease without a veterinary exam and appropriate testing. (Cornell Vet College)
Can a horse recover from neurological disease?
Some horses recover well, especially when the cause is recognised early and treated appropriately. Others may retain permanent deficits. For EPM, around 60 to 70% of treated horses improve, but complete recovery is less common and relapse can occur. (University of Minnesota Extension)
Is a wobbly horse always an emergency?
Not always, but it should always be taken seriously. Sudden onset, worsening signs, fever, urine dribbling, difficulty swallowing, collapse, trauma or multiple affected horses make it urgent.
Can EHV cause neurological signs in vaccinated horses?
Yes. EHV vaccination can help reduce respiratory disease, abortion risk and viral shedding, but there is currently no vaccine labelled to prevent the neurologic form, EHM. (Equine Disease Communication Center)
Should I isolate a neurologic horse?
If infectious disease is possible, yes. Fever, recent travel, show exposure, nasal discharge, multiple affected horses or EHV concern should trigger isolation while waiting for veterinary advice. If the signs look traumatic or non-infectious, the horse still needs to be kept safe and quiet.
The Bottom Line
A wobbly horse needs a proper diagnosis, not a guess.
EPM, Wobblers and EHV are three major causes owners hear about, but they are not interchangeable. EPM often causes asymmetric neurologic signs and is commonly overdiagnosed from blood tests alone. Wobblers involves spinal cord compression in the neck and often causes more symmetrical incoordination. EHV can start with fever and become a contagious neurologic emergency.
The signs that change the urgency are fever, rapid worsening, urine dribbling, difficulty swallowing, collapse, inability to stand, recent travel, multiple horses affected or disease risk in your region.
If your horse is mildly off but stable, book a veterinary assessment.
If your horse is suddenly weak, wobbly, febrile, unable to urinate, struggling to swallow or unsafe to move, do not wait.
Neurological problems can be frightening, but early action gives your horse the best chance and protects the rest of the property when contagious disease is possible.
If you are unsure whether your horse’s stumbling, weakness, muscle loss, head tilt, fever or wobbliness is urgent, ASK A VET™ can help you organise the signs, track progression and decide when veterinary care should not wait.