West Nile Virus in Horses: Symptoms, Vaccine Schedule and Prevention

By Dr Duncan Houston

A horse can appear normal one day and develop muscle trembling, hindlimb weakness or severe incoordination the next.

West Nile virus remains an important cause of neurological disease in horses across North America. It may receive less publicity than it did when first identified in the United States, but confirmed equine cases continue to occur during mosquito seasons, particularly among horses that are unvaccinated or have incomplete vaccination histories. (Equine Disease Communication Center)

The good news is that West Nile virus is one of the serious equine diseases we can meaningfully reduce through vaccination and sensible mosquito control.

Quick Answer

West Nile virus is a mosquito-borne neurological disease that can cause weakness, muscle fasciculations, incoordination, difficulty swallowing, recumbency and death in horses. The American Association of Equine Practitioners considers West Nile vaccination a core part of healthcare for all horses in North America.

Previously vaccinated adult horses are generally boosted annually before mosquito season. An unvaccinated adult usually needs a two-dose primary series given approximately three to six weeks apart, depending on the vaccine product. Any sudden neurological abnormality should be treated as an emergency. (AAEP)

What Is West Nile Virus?

West Nile virus is a flavivirus transmitted primarily by mosquitoes.

The virus circulates naturally between birds and mosquitoes. A mosquito becomes infected after feeding on a bird carrying the virus, then transmits it when it bites another bird, a horse, a person or another susceptible mammal. (CDC)

Horses and people are considered dead-end hosts. This means they do not normally develop enough virus in their bloodstream to infect another mosquito and continue the transmission cycle.

West Nile virus is therefore not ordinarily spread:

• From horse to horse

• Through shared buckets or tack

• By coughing or nasal discharge

• From a living horse directly to a person

A horse does not need to travel, compete or meet another horse to become infected. One infected mosquito is enough. (CDC)

Is West Nile Virus Still a Risk?

Yes.

West Nile virus is established across the continental United States and occurs in Canada, Mexico and other parts of the world. It is now considered endemic in North America, meaning some level of virus activity can be expected from year to year. (AAEP)

However, annual case numbers fluctuate considerably.

The EDCC received reports of 244 equine West Nile cases in 2023 and 153 in 2024. These figures do not capture every case because reporting varies between states and provinces, but they demonstrate why it is misleading to describe the pattern as a simple year-on-year increase. (Equine Disease Communication Center)

The more useful question is not whether national numbers are up or down this particular year. It is:

Is your horse protected before infected mosquitoes become active locally?

West Nile risk is influenced by:

• Local mosquito populations

• Temperature and rainfall

• Standing water

• Bird and mosquito infection levels

• The length of the regional mosquito season

• The horse’s vaccination history

• The horse’s age and immune status

In many temperate areas, equine cases become more common during late summer and autumn. In warmer climates, mosquitoes may remain active for much more of the year. (Equine Disease Communication Center)

How Dangerous Is West Nile Virus for Horses?

Many infected horses never develop recognisable clinical illness.

When neurological disease develops, however, the consequences can be severe. The AAEP estimates that approximately one-third of horses showing clinical West Nile disease die or are euthanised. (AAEP)

Recumbency is one of the most important prognostic signs. In a clinical study of 46 affected horses, mortality was approximately 30%, while 71% of horses that became recumbent were euthanised. (PubMed)

Survival does not always mean immediate or complete recovery. The AAEP cites data showing that around 40% of horses surviving the acute illness still had gait or behavioural abnormalities six months after diagnosis. Other studies have found that many residual signs improve over a longer recovery period, sometimes taking up to 12 months. (AAEP)

Possible long-term problems include:

• Hindlimb weakness

• Persistent stumbling

• Reduced balance

• Muscle loss

• Reduced stamina

• Behavioural change

• Increased startle responses

• Periods of unusual drowsiness

• Reduced ability to return safely to previous work

A horse recovering from West Nile disease should undergo a veterinary neurological reassessment before returning to riding, driving or strenuous exercise.

What Are the Signs of West Nile Virus in Horses?

Clinical signs can vary depending on which areas of the brain and spinal cord are affected.

Early or less specific signs

Early signs may include:

• Reduced appetite

• Depression

• Unusual drowsiness

• Mild fever

• Reduced interaction with people or other horses

• Apparent colic-like behaviour

• Excessive sweating

Fever is not present in every affected horse. The absence of a high temperature should never be used to rule out West Nile disease. (Equine Disease Communication Center)

Neurological signs

More characteristic signs include:

• Fine muscle trembling around the muzzle, face or neck

• Muscle fasciculations

• Stumbling or swaying

• Hindlimb weakness

• Crossing the limbs while walking

• Leaning against walls or fences

• Abnormal placement of the feet

• Difficulty turning

• Facial weakness or a drooping lip

• Head tilt

• Tongue weakness

• Difficulty swallowing

• Teeth grinding

• Altered awareness or behaviour

• Blindness or impaired vision

• Partial or complete paralysis

• Inability to stand

• Seizures

• Death

The onset of neurological disease can be sudden and progressive. A horse that is mildly uncoordinated in the morning may be unable to rise later that day. (direct.aphis.usda.gov)

How Worried Should You Be?

Lower immediate risk

The horse:

• Is fully vaccinated

• Is bright, eating and moving normally

• Has no neurological abnormalities

• Is not known to have missed a booster

• Lives in an area where mosquito control is being maintained

Continue normal monitoring and review the vaccine record before the local mosquito season.

Vaccination substantially reduces risk, but it does not justify ignoring neurological signs if they develop.

Moderate risk

The horse:

• Is several weeks or months overdue for a booster

• Has an uncertain vaccination history

• Received only the first dose of its primary series

• Is entering a period of increased mosquito activity

• Is travelling into an area with current West Nile cases

• Lives near extensive standing water

Contact your veterinarian to review the vaccination plan. Do not assume that one initial injection provides complete primary protection.

High risk

The horse:

• Has never been vaccinated

• Has an incomplete primary course

• Lives where mosquitoes remain active for much of the year

• Is younger than five or older than 15

• Has recently received immunosuppressive treatment

• Has chronic disease affecting immune function

• Lives near recently reported equine or human cases

AAEP guidance identifies juvenile and geriatric horses as potentially more susceptible and recommends considering more frequent or strategically timed revaccination in horses at increased risk. (AAEP)

Critical

Treat the situation as an emergency when any horse develops:

• Sudden incoordination

• Hindlimb weakness

• Muscle fasciculations

• Difficulty swallowing

• Abnormal behaviour or awareness

• Blindness

• Repeated falling

• Recumbency

• Seizures

• Rapid neurological deterioration

Call your veterinarian immediately.

When Is Suspected West Nile Virus an Emergency?

Every horse with sudden neurological signs requires urgent veterinary assessment.

Do not ride, lunge or repeatedly walk an uncoordinated horse to see whether it “loosens up.” An ataxic horse may fall without warning and can seriously injure itself or the people around it.

While waiting for your veterinarian:

1. Move other horses away if this can be done safely.

2. Keep the affected horse in a quiet, enclosed area with secure footing.

3. Remove buckets, feeders or equipment that could cause injury.

4. Keep people clear of the horse’s limbs and escape path.

5. Do not attempt to trailer a severely uncoordinated horse without veterinary instructions.

6. Record when the signs began and how quickly they are changing.

7. Locate the horse’s complete vaccination record.

8. Take a short video only when it is safe to do so.

9. Record temperature, appetite, urination and manure production.

10. Avoid placing inexperienced handlers near the horse.

West Nile virus itself is not contagious, but other conditions causing similar signs may be contagious or have human-health implications. AAEP guidance recommends approaching acute neurological disease cautiously and considering EHV-1, rabies, West Nile virus and the equine encephalitis viruses until testing narrows the diagnosis. (AAEP)

This means sensible temporary precautions are appropriate:

• Separate the horse from the group

• Do not share equipment

• Handle healthy horses first

• Wash hands and footwear

• Restrict unnecessary visitors

• Follow your veterinarian’s biosecurity instructions

Do not skip biosecurity simply because West Nile is high on the list.

What Else Can Look Like West Nile Virus?

Muscle trembling and incoordination are not specific to West Nile disease.

Important differential diagnoses include:

Equine herpesvirus myeloencephalopathy

EHV-1 can cause fever, hindlimb weakness, urine dribbling, reduced tail tone, incoordination and recumbency.

Unlike West Nile virus, EHV-1 is contagious and may spread through respiratory secretions, direct contact and contaminated equipment. (APHIS)

Eastern, Western or Venezuelan equine encephalitis

These mosquito-borne viruses can also cause severe brain inflammation, depression, behaviour change, blindness, seizures and recumbency.

Geographical likelihood varies, but they remain important rule-outs in appropriate regions. (direct.aphis.usda.gov)

Rabies

Rabies can cause behavioural change, weakness, difficulty swallowing, hypersensitivity, incoordination, paralysis or sudden death.

Because rabies is fatal and poses a serious risk to people, it must remain on the differential list for an unexplained neurological horse, even when another disease initially appears more likely. (Equine Disease Communication Center)

Equine protozoal myeloencephalitis

EPM can cause asymmetric weakness, muscle loss, ataxia and cranial nerve abnormalities in horses that live in or have travelled through affected regions of the Americas. (AAEP)

Other neurological or metabolic conditions

Other possibilities include:

• Botulism

• Cervical spinal cord compression

• Head or spinal trauma

• Toxicity

• Hepatic encephalopathy

• Intestinal hyperammonaemia

• Severe electrolyte abnormalities

• Brain or spinal tumours

• Other inflammatory diseases of the nervous system

The horse’s vaccination record, geographical location, exposure history and neurological examination help determine which tests are most appropriate.

How Is West Nile Virus Diagnosed?

Diagnosis is based on the combination of:

• Compatible neurological signs

• Geographical and seasonal exposure

• Vaccination history

• Neurological examination

• Laboratory testing

• Exclusion of other important diseases

IgM antibody testing

A West Nile IgM capture ELISA performed on serum is commonly used to support the diagnosis of recent infection.

IgM is relatively short-lived and usually indicates recent exposure. However, vaccination can occasionally produce a low IgM response, so the laboratory and veterinarian must be given the full vaccination history. (Canadian Food Inspection Agency)

IgG testing

IgG may indicate:

• Previous vaccination

• Previous natural exposure

• A developing immune response to current infection

A single positive IgG result cannot reliably distinguish vaccination from active disease. Paired blood samples taken approximately 10 to 14 days apart may be needed in some cases to demonstrate a meaningful rise in antibody levels. (Canadian Food Inspection Agency)

Cerebrospinal fluid testing

Your veterinarian may collect cerebrospinal fluid when the clinical findings require further investigation.

CSF can assist with West Nile testing and with ruling out other neurological diseases, including EPM. It is not required in every suspected West Nile case. (AAEP Pubs)

PCR testing

PCR may identify viral genetic material, but West Nile virus is often present only briefly and at low levels in equine blood.

For this reason, PCR of routine blood or CSF samples is generally less useful than appropriate serology for antemortem diagnosis. Brain and spinal cord tissue are more useful for virus detection after death. (Canadian Food Inspection Agency)

Additional testing

Depending on the case, your veterinarian may also recommend:

• Complete blood count

• Biochemistry and electrolytes

• EHV-1 PCR testing

• EEE or WEE testing

• EPM testing

• Blood ammonia measurement

• Toxicology testing

• Cervical radiographs or advanced imaging

• Other region-specific infectious disease tests

Reporting requirements vary by location. Your veterinarian will coordinate with the relevant animal health authorities when required.

Is There a Treatment for West Nile Virus?

There is no specific antiviral cure routinely available for equine West Nile disease.

Treatment is supportive and directed at controlling inflammation, maintaining hydration and nutrition, preventing injury and helping the horse through the neurological phase. (direct.aphis.usda.gov)

Treatment may include:

• Anti-inflammatory medication

• Intravenous or oral fluids

• Nutritional support

• Safe confinement

• Deep bedding

• Assistance for horses having difficulty standing

• Sling support in carefully selected cases

• Treatment of secondary injuries

• Urinary bladder management

• Seizure control

• Protection from self-trauma

• Intensive nursing care

Recumbent horses require particularly demanding care. Prolonged inability to stand can lead to muscle damage, pressure injury, nerve injury, respiratory complications and severe distress.

The horse’s ability to remain standing, eat, drink and maintain awareness strongly influences prognosis.

Can a Horse Recover From West Nile Virus?

Yes. Many horses with mild to moderate disease recover.

Recovery may take weeks or months, and neurological improvement is not always smooth. Some horses appear much better, then show weakness or fatigue when exercise is reintroduced.

The prognosis is generally better when the horse:

• Remains standing

• Continues eating and drinking

• Has mild rather than severe ataxia

• Does not develop seizures

• Can swallow normally

• Responds during the first few days of supportive care

The prognosis becomes more guarded when the horse:

• Becomes recumbent

• Cannot remain upright

• Develops severe cranial nerve dysfunction

• Cannot swallow safely

• Experiences seizures

• Develops rapidly progressive paralysis

• Sustains serious secondary injuries

A previous level of athletic performance is not guaranteed. A horse should not return to ridden work until coordination, strength and behaviour have been reassessed.

Is West Nile Vaccination Recommended for Every Horse?

In North America, yes.

The AAEP classifies West Nile vaccination as a core vaccine. Core vaccines are recommended broadly because the disease has potentially severe consequences, the exposure risk is widespread and licensed vaccines provide substantial benefit. (AAEP)

This recommendation includes horses that:

• Never attend shows

• Rarely leave the farm

• Live alone

• Are retired

• Spend most of their time indoors

• Have little contact with other horses

West Nile exposure comes from mosquitoes rather than horse movement or social contact.

Outside North America, vaccination recommendations and licensed product availability vary. Owners should follow local veterinary and animal health guidance.

What Is the West Nile Vaccine Schedule?

The exact schedule depends on the vaccine product, age, pregnancy status and previous vaccination history.

Previously vaccinated adult horses

A previously vaccinated adult horse is generally given:

• One booster annually

• Ideally before the local mosquito season begins

In areas with prolonged or year-round mosquito activity, or where an individual horse has increased susceptibility, a veterinarian may recommend a more frequent or differently timed booster. (AAEP)

Unvaccinated adults or horses with an unknown history

Most licensed products require:

• Two initial doses

• Approximately three to six weeks apart, depending on the product

• Revaccination at 12 months

The product label must be followed because some vaccines specify a three-to-four-week interval while others specify four to six weeks. (AAEP)

The second dose is essential. A horse that receives only the first injection should not be regarded as having completed its primary protection. (AAEP)

Pregnant mares

For a previously vaccinated pregnant mare, AAEP guidance recommends a booster approximately four to six weeks before foaling.

Product selection matters because pregnancy-related label claims differ. The attending veterinarian should confirm which vaccine is suitable for the mare. (AAEP)

Foals from vaccinated mares

Foals from vaccinated mares commonly receive:

• A three-dose primary series

• Beginning at four to six months of age

• A second dose around four weeks later

• A third dose at approximately 10 to 12 months, before the next mosquito season

The exact schedule varies slightly between vaccine platforms. (AAEP)

Foals from unvaccinated mares

These foals may begin vaccination earlier, at approximately three to four months of age, using a veterinarian-directed three-dose course.

Where possible, the primary course should be completed before the period of highest mosquito exposure. (AAEP)

Does Every Horse Need a Booster Twice a Year?

No.

Twice-yearly West Nile vaccination is not automatically necessary for every horse.

An annual booster before mosquito season is the standard recommendation for previously vaccinated adult horses. More frequent boosters may be appropriate when:

• Mosquitoes remain active throughout the year

• The horse lives in an endemic high-risk area

• Local cases are occurring

• The horse will travel into a high-risk region

• The horse is very young or geriatric

• The horse has limited or uncertain immunity

• The timing of the annual booster leaves a gap during peak exposure

The decision should be based on local risk and the individual horse, not on a universal calendar rule. (AAEP)

When Should the Vaccine Be Given?

Vaccination should be completed before likely mosquito exposure.

AAEP owner guidance advises arranging vaccination at least approximately one month before mosquito season so protective immunity has time to develop. This is especially important for an unvaccinated horse that still needs both doses of the primary course. (AAEP)

Do not wait until a nearby horse is diagnosed before starting the first injection.

A sensible timeline is:

1. Identify when mosquitoes usually become active locally.

2. Count backwards far enough to complete the required primary series.

3. Allow additional time for the immune response to develop.

4. Review the schedule earlier when travel is planned.

5. Confirm all dates using the exact product label.

A first dose given during an outbreak is better than doing nothing, but it does not create immediate protection.

Can a Vaccinated Horse Still Develop West Nile Disease?

Yes, although the risk is substantially reduced.

No vaccine guarantees complete protection in every individual. Breakthrough disease may occur because of:

• An incomplete primary course

• A missed booster

• Vaccination too close to exposure

• Incorrect vaccine storage

• Improper administration

• An individual poor immune response

• Immunosuppressive disease or medication

• Exceptionally heavy exposure

Licensed vaccines have demonstrated protection in challenge studies, and widespread vaccination has greatly reduced the number of equine cases compared with the early years of West Nile activity in North America. (PubMed)

The practical message is not that vaccination makes disease impossible. It is that an appropriately completed vaccine program provides the strongest available protection.

How Can You Reduce Mosquito Exposure?

Vaccination is the foundation of prevention, but mosquito control provides a second layer.

Remove standing water

Inspect the property for water collecting in:

• Old tyres

• Buckets

• Feed tubs

• Tarpaulins

• Wheelbarrows

• Blocked gutters

• Plant pots

• Machinery

• Fence posts

• Uneven ground

• Unused water tanks

Small containers can produce large numbers of mosquitoes.

Turn containers upside down, drill drainage holes where appropriate and correct areas where rainwater repeatedly pools. (direct.aphis.usda.gov)

Clean troughs regularly

Empty, scrub and refill small water troughs regularly, with weekly cleaning a useful practical target where feasible.

Do not deprive horses of drinking water to control mosquitoes. Arrange an alternative clean supply while a trough is being emptied or maintained. (Penn State Extension)

Manage water that cannot be emptied

Large ponds, dams or permanent water sources require a different plan.

Depending on local regulations and the water source, options may include:

• Improving drainage

• Introducing suitable mosquito-eating fish

• Using an approved biological larvicide

• Obtaining advice from local mosquito-control or extension services

Do not add household chemicals, oils or unapproved pesticides to horse water supplies. The EDCC includes mosquito-feeding fish among possible controls for suitable tanks or ponds. (Equine Disease Communication Center)

Use fans

Mosquitoes are relatively weak fliers.

Fans placed safely in stables or sheltered resting areas may reduce their ability to land and feed on horses. Electrical equipment must be installed securely and kept away from water, bedding and curious teeth. (direct.aphis.usda.gov)

Use screened stabling

Screens on stable windows and doors can reduce mosquito entry.

Repair holes and ensure doors fit properly. A stable is most protective when it is screened, ventilated and supported by fans. Simply moving a horse into a warm, unscreened barn full of mosquitoes achieves rather less than the brochure promised.

Consider peak mosquito activity

Many important mosquito species are active around dusk, overnight and around dawn.

Where practical, keep horses in screened or fan-protected areas during the locally relevant peak feeding periods. Some mosquito species also feed during daylight, so this should not be the only protection used. (direct.aphis.usda.gov)

Apply equine-approved repellent

Use a mosquito repellent labelled for horses and follow its directions carefully.

Consider:

• How often it must be reapplied

• Whether rain or sweating reduces effectiveness

• Whether the product is suitable for sensitive skin

• Whether it can be used around the face

• Competition or racing restrictions

Homemade mixtures may be ineffective and can irritate the skin. Commercially registered products have undergone safety testing that kitchen-counter chemistry generally has not. (University of Minnesota Extension)

Use physical barriers appropriately

Fly sheets, neck covers, masks and boots may reduce the number of exposed bite sites.

They should fit correctly and be checked for rubbing, overheating and displacement. They do not cover the entire horse and do not replace vaccination, property management or repellent.

Follow local disease alerts

Monitor reports from:

• Your veterinarian

• State or provincial animal health authorities

• Local mosquito-control programs

• The Equine Disease Communication Center

• Regional veterinary diagnostic laboratories

Local activity is more useful for immediate decision-making than waiting for West Nile disease to return to national headlines.

What Should You Do Right Now?

1. Find the exact vaccine record

Do not rely on notes such as “spring shots” or “five-way.”

Confirm:

• Product name

• Diseases included

• Date given

• Number of primary doses

• Date the next dose was due

• Previous vaccine reactions

• Whether the horse was vaccinated before you acquired it

2. Identify incomplete courses

A horse that received one initial West Nile injection but never received the second dose has not completed the standard primary series.

Contact your veterinarian rather than guessing whether to restart or continue the course.

3. Review local exposure

Consider:

• Mosquito season length

• Recent rain

• Standing water

• Nearby disease alerts

• Travel plans

• Age and health of the horse

• Whether mosquitoes remain active year-round

4. Walk the property

Perform a weekly mosquito-breeding inspection during warm weather.

Look behind sheds, under tarps and inside forgotten equipment. The half-filled bucket nobody has touched since last winter is often running a small mosquito nursery with admirable commitment.

5. Prepare an emergency plan

Know:

• Which veterinarian provides emergency care

• Which hospital can accept a neurological horse

• How to safely confine the horse

• Where vaccine records are stored

• Who should handle the horse

• How other horses would be separated if necessary

A plan made before an emergency tends to contain fewer people shouting contradictory ideas beside a horse that can barely stand.

Common West Nile Prevention Mistakes

Assuming a horse that never travels is safe

West Nile virus is transmitted by mosquitoes. The horse does not need contact with another horse.

Giving only one dose of the initial course

The second dose is required to complete the standard primary response.

Waiting until local cases appear

Protective immunity takes time to develop. Vaccination should be completed before peak exposure.

Treating six-month boosters as mandatory for every horse

Some horses need more frequent vaccination, but annual vaccination is the standard starting point. Timing should reflect actual risk.

Relying on vaccination alone

Vaccination is the most important protection, but no vaccine is perfect. Standing-water control, fans, screens and repellents remain useful.

Waiting for a fever

Some affected horses have no obvious fever. Sudden weakness, trembling or incoordination is enough to justify emergency assessment.

Forcing an ataxic horse to walk

Walking does not diagnose or treat West Nile virus. It can cause the horse to fall and injure itself or its handlers.

Assuming every neurological horse has West Nile

EHV-1, rabies and other diseases can look similar. Until the diagnosis is clearer, use sensible biosecurity and avoid unnecessary exposure.

Trusting mosquito traps as the whole control plan

Traps may catch some mosquitoes but are unlikely to eliminate the population or replace source reduction, vaccination and bite prevention. (University of Minnesota Extension)

A Practical West Nile Prevention Checklist

Before mosquito season:

• Review every horse’s vaccination record

• Complete primary courses early

• Schedule annual boosters before vector activity

• Discuss whether any horse needs a risk-based additional booster

• Clean troughs and drainage systems

• Remove unnecessary water-holding containers

• Repair screens

• Install fans safely

• Purchase an equine-approved repellent

• Check emergency contact details

• Monitor local disease alerts

During mosquito season:

• Inspect the property weekly

• Reapply repellent according to the label

• Keep troughs clean

• Check screens and fans

• Watch horses for trembling, weakness or behavioural change

• Review travel destinations for disease activity

• Contact your veterinarian promptly after any neurological change

Frequently Asked Questions

Is West Nile virus contagious between horses?

No. Horses are dead-end hosts and do not normally transmit West Nile virus directly to other horses or people. However, a neurological horse should initially be managed cautiously because contagious diseases such as EHV-1 can cause similar signs. (CDC)

Does an indoor horse still need a West Nile vaccine?

Yes. Mosquitoes can enter barns, and indoor living does not eliminate exposure. West Nile vaccination is considered a core recommendation for all horses in North America. (AAEP)

How often should a horse receive a West Nile booster?

Previously vaccinated adult horses are generally boosted annually before mosquito season. Some horses in areas with prolonged mosquito activity or increased individual risk may need more frequent vaccination. (AAEP)

Can a horse survive West Nile virus?

Yes. Many mildly or moderately affected horses recover, but approximately one-third of clinically affected horses die or are euthanised. Horses that become recumbent have a poorer prognosis, and some survivors retain neurological abnormalities. (AAEP)

Does a positive antibody test always mean active West Nile disease?

No. IgG antibodies may reflect vaccination or previous natural exposure. IgM is more supportive of recent infection, but vaccination history and clinical signs must still be considered when interpreting results. (Canadian Food Inspection Agency)

Final Thoughts

West Nile virus is no longer a new disease, but it remains a serious one.

The national case count may rise or fall from one season to the next. That does not change the practical advice for an individual horse. Complete the primary vaccine course, administer boosters before likely mosquito exposure and reduce breeding sites around the property.

Do not wait for a dramatic collapse before responding to neurological signs. Fine muzzle trembling, unusual drowsiness, hindlimb weakness or mild stumbling may be the first warning that something serious is developing.

Vaccination cannot remove every risk, but it gives the horse a far better chance. Mosquito management adds another layer, and rapid veterinary assessment matters when neurological disease occurs.

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Use ASK A VET™ to store your horse’s vaccine dates, medication records, symptom notes and videos. If you are unsure whether weakness, muscle trembling or unusual behaviour is urgent, tailored veterinary support can help you organise the information while arranging direct examination by your veterinarian.