Contagious Disease Prevention in Horses: Stable, Travel and Event Biosecurity
In this article
Contagious Disease Prevention in Horses: Stable, Travel and Event Biosecurity
By Dr Duncan Houston
Contagious disease control is not about panic. It is about building boring, repeatable habits that stop one sick horse becoming a whole-property problem.
Horse owners usually think about contagious disease when there is an outbreak: a horse returns from a show with a fever, a new arrival starts coughing, a strangles case appears nearby, or an EHV alert suddenly circulates through every stable group chat within 11 seconds.
But the best biosecurity does not start during an outbreak.
It starts before one.
Contagious diseases such as equine herpesvirus, strangles, equine influenza and equine coronavirus can spread through direct horse contact, respiratory droplets, manure, contaminated buckets, tack, grooming tools, trailers, clothing, hands and shared equipment. The strongest protection is not one product or one vaccine. It is a system: vaccination, quarantine, hygiene, temperature monitoring, separate equipment, early isolation and clear communication.
Quick Answer
To prevent contagious disease in horses, every stable should use routine biosecurity: quarantine new and returning horses, avoid shared buckets and equipment, wash hands between horses, monitor temperatures, isolate sick horses immediately, clean and disinfect properly, and work with a veterinarian when fever, cough, nasal discharge, diarrhea, swollen lymph nodes or neurologic signs appear. AAEP defines equine biosecurity as practices that prevent disease introduction and reduce spread in horse populations, especially at stables and events with frequent horse movement. (AAEP)
If a horse has a fever above 101.5°F or 38.6°C, nasal discharge, coughing, diarrhea, depression, swollen lymph nodes, neurologic signs or recent exposure to a sick horse, treat it as a biosecurity concern until your veterinarian says otherwise. EDCC recommends twice daily temperature monitoring for exposed horses, ideally 12 hours apart, and reporting temperatures above 101.5°F to a veterinarian. (Equine Disease Communication Center)
What Is Biosecurity in Horses?
Biosecurity means the practical steps used to reduce the risk of infectious disease entering, spreading through or leaving a horse property.
That sounds very official. In real life, it means:
• Do not let sick horses mix with healthy horses
• Do not share contaminated equipment
• Do not ignore fever
• Do not move exposed horses casually
• Do not bring new horses straight into the main herd
• Do not spray disinfectant over manure and call it a day
AAEP states that a proper biosecurity plan should include routine preventative protocols and response protocols for confirmed or suspected infectious disease. It also stresses that each equine facility is different, so plans should be practical for the specific property, not copied blindly from somewhere else. (AAEP)
That is the key. A two-horse backyard paddock, a breeding farm, a show barn, a boarding stable and a racing yard all need different versions of the same principle:
Keep disease pathways as short and controlled as possible.
How Contagious Diseases Spread Between Horses
Contagious disease can spread through direct contact, indirect contact, aerosols, manure contamination and people.
Direct horse-to-horse contact
This includes nose-to-nose contact, mutual grooming, shared fence lines, shared water points, close stabling and direct contact with nasal discharge, saliva, abscess drainage or manure.
This matters especially for respiratory diseases such as strangles, equine influenza and equine herpesvirus.
Indirect spread through fomites
A fomite is any object that can carry infectious material from one horse to another.
Common fomites include:
• Water buckets
• Feed tubs
• Hay nets
• Grooming brushes
• Tack
• Lead ropes
• Halters
• Thermometers
• Muck forks
• Wheelbarrows
• Trailers
• Stable doors
• Wash bays
• Human hands, boots and clothing
This is where many outbreaks quietly spread. The horse may never touch another horse, but the handler does.
Respiratory droplets and aerosols
Coughing, snorting and close shared air space can spread respiratory pathogens. Equine influenza can spread before obvious signs appear and can also spread indirectly through contaminated objects such as clothing, equipment and brushes. (CDC)
Fecal-oral spread
Some diseases spread through manure contamination. Equine coronavirus is a classic example. ECoV spreads mainly through the fecal-oral route, and infected horses may continue shedding virus in manure after signs improve. (AAEP)
This is why manure management is biosecurity, not just stable cleanliness.
The Most Important Contagious Diseases To Think About
Equine herpesvirus
Equine herpesvirus, especially EHV-1 and EHV-4, can cause respiratory disease, abortion and neurologic disease. EHV-1 myeloencephalopathy, also called EHM, can cause hindlimb weakness, ataxia, urine dribbling and recumbency. Fever may be the only early sign, and AAEP recommends twice daily temperature monitoring in at-risk horses to avoid missing it.
EHV is one of the reasons fever at a show, boarding facility or breeding farm should never be brushed off.
Strangles
Strangles is caused by Streptococcus equi subspecies equi. It is highly contagious and spreads through direct contact and contaminated surfaces. EDCC notes that horses can contract strangles from other horses or contaminated surfaces, and AAEP states that horses with lymph node swelling, nasal discharge or fever should be considered potentially infected and isolated immediately. (Equine Disease Communication Center)
The hidden problem with strangles is carrier horses. Some recovered horses can harbour bacteria in the guttural pouches and look normal while still posing a risk. Cornell notes that guttural pouch endoscopy and washes are used to investigate carrier status, and repeated negative guttural pouch washes may be needed to confirm negative status. (Cornell Vet College)
Equine influenza
Equine influenza is a highly contagious respiratory virus. It can spread rapidly in groups of susceptible horses, especially where horses travel, mix and share air space. Infected horses can shed virus before obvious signs appear, which makes pre-event health checks and temperature logs valuable. (CDC)
Equine coronavirus
Equine coronavirus is an intestinal virus of horses, not the same as COVID-19. It usually causes fever, dullness, reduced appetite, soft manure, diarrhea or mild colic signs. It spreads mainly through manure contamination, and positive horses should remain isolated with strict biosecurity and manure management. (AAEP)
Diarrhea-causing infections
Salmonella, clostridial disease, rotavirus in foals and other enteric infections can spread through manure, bedding, contaminated equipment and hands. Any horse with fever and diarrhea should be treated as potentially infectious until proven otherwise.
Skin diseases
Ringworm and other infectious skin conditions can spread through tack, rugs, saddle pads, grooming gear, stable surfaces and direct contact. They are usually not life-threatening, but they are extremely good at making a barn miserable.
Biosecurity Risk Framework
| Risk level | What it looks like | What it may mean | What to do |
|---|---|---|---|
| Low risk | Horse is bright, normal temperature, eating well, no cough, no discharge, no diarrhea, no recent travel | Routine disease risk | Keep normal hygiene, vaccination and monitoring routines |
| Moderate risk | New arrival, returned from show, mild dullness, mild nasal discharge, mild soft manure, recent contact with unknown horses | Early infectious disease or travel stress possible | Separate from main herd and monitor temperature twice daily |
| High risk | Fever, cough, thick nasal discharge, diarrhea, swollen lymph nodes, reduced appetite, known exposure | Contagious disease possible | Isolate immediately and call your veterinarian |
| Critical | Neurologic signs, urine dribbling, difficulty rising, respiratory distress, profuse diarrhea, severe depression, multiple horses affected | Serious outbreak or emergency disease possible | Stop movement and seek urgent veterinary care immediately |
The main decision point is simple:
A horse with fever and recent travel, new arrival status or exposure to sick horses should be treated as infectious until proven otherwise.
What Temperature Is Concerning in a Horse?
A commonly used fever threshold in equine infectious disease monitoring is above 101.5°F or 38.6°C. AAEP’s EHV guidance lists fever as body temperature above 101.5°F or 38.6°C, and EDCC recommends reporting exposed horses with temperatures above 101.5°F to a veterinarian.
Temperature should be taken:
• Before exercise
• Before anti-inflammatory drugs such as phenylbutazone or flunixin
• At roughly the same times each day
• Twice daily during quarantine or exposure monitoring
• With a thermometer assigned to that horse or group
A temperature straight after hard work, travel or hot weather needs context. But a fever in a horse that has recently travelled, mixed with unknown horses or had exposure to illness should not be casually dismissed.
Quarantine vs Isolation: The Difference Matters
These two words are often used interchangeably, but they are not the same.
Quarantine
Quarantine is for horses that appear healthy but may have been exposed.
Examples:
• New horse arriving at the property
• Horse returning from a show
• Horse returning from sales
• Horse exposed to an infected horse
• Horse arriving from a high-turnover facility
The horse is not necessarily sick. The goal is to keep it separate long enough to see whether signs develop.
Isolation
Isolation is for horses that are sick or suspected of being infectious.
Examples:
• Fever
• Cough
• Nasal discharge
• Diarrhea
• Swollen lymph nodes
• Abscess drainage
• Neurologic signs
• Positive infectious disease test
The goal is to protect all other horses while the sick horse is assessed, tested and managed.
EDCC recommends identifying and isolating potentially exposed horses, restricting movement, setting access barriers, posting signage and monitoring rectal temperatures twice daily. (Equine Disease Communication Center)
In practice:
Quarantine is for “might be exposed.” Isolation is for “might be infectious.”
Both matter.
How Long Should New or Returning Horses Be Separated?
For routine new arrivals or horses returning from events, a practical minimum is often 14 days of separation and twice daily monitoring. EDCC recommends that new and returning horses be kept separate and monitored for at least 14 days, including twice daily temperature checks and health checks for appetite, water intake, urination, manure and signs of illness. (Equine Disease Communication Center)
For higher-risk situations, 21 days or longer may be more appropriate, especially after known exposure to EHV, strangles, influenza, equine coronavirus or an active event outbreak. The exact length should be set with your veterinarian and local animal health guidance.
A strong quarantine setup includes:
• Separate stable, paddock or barn area
• No nose-to-nose contact
• Separate feed and water containers
• Separate grooming tools
• Separate thermometer
• Separate mucking tools
• Clear signage
• Limited handlers
• Handling quarantined horses last
• Twice daily temperature log
• Written record of appetite, manure and behaviour
If you cannot create a perfect quarantine area, create the best one possible. Distance, separate tools and handling order are still useful.
Daily Stable Biosecurity: The Habits That Matter
Good biosecurity is mostly boring. That is why it works.
Use individual equipment
Each horse should ideally have its own:
• Feed bucket
• Water bucket
• Grooming kit
• Halter
• Lead rope
• Thermometer
• Towels
• Rugs where practical
If equipment must be shared, it should be cleaned and disinfected between horses.
Avoid communal water
Communal water is convenient until it becomes a disease distribution service.
Use individual buckets where possible, especially at shows, boarding barns, quarantine areas and during outbreaks. CDFA event guidance specifically advises avoiding communal water sources and limiting nose-to-nose contact. (CalDFA)
Wash hands between horses
Hand hygiene matters most when moving between groups.
Wash or sanitise:
• Before feeding
• After handling a sick horse
• After touching another person’s horse
• After cleaning manure
• Before touching a horse’s muzzle
• Before handling foals or pregnant mares
• Between quarantine and resident horses
Alcohol-based hand sanitiser can help when hands are not visibly dirty, but soap and water are better when hands are contaminated with dirt, saliva, manure or discharge.
Handle horses in the right order
The safest order is:
-
Healthy resident horses
-
New or returning horses in quarantine
-
Sick or isolated horses
Then wash hands, change clothes or coveralls, clean boots and disinfect equipment as appropriate.
Control visitor access
Boarding barns, training yards and breeding farms should know who is entering the property.
Useful policies include:
• Visitor sign-in
• Restricted access to quarantine areas
• No touching horses without permission
• Hand sanitiser stations
• Clear signs around isolation areas
• Separate parking for visitors where needed
• Staff training on what signs must be reported
EDCC recommends access management plans, controlled zones and training everyone who handles horses or enters the property. (Equine Disease Communication Center)
Event and Show Biosecurity
Horse shows are where biosecurity gets tested.
A showground brings together horses from different barns, vaccination histories, transport routes, trainers, handlers and disease risks. Even with good event rules, exposure can occur. CDFA notes infectious agents may be brought to and spread at equine events by horses, people, other animals, vehicles, equipment, insects, ticks, birds, rodents, feed, waste and water. (CalDFA)
Before the event
Do not travel a sick horse.
Cancel or delay travel if your horse has:
• Fever
• Cough
• Nasal discharge
• Diarrhea
• Poor appetite
• Lethargy
• Swollen lymph nodes
• Recent exposure to a contagious horse
• Neurologic signs
CDFA guidance states that horses with nasal discharge, persistent coughing, neurologic signs, ataxia or hindlimb weakness should not be shipped to an event. (CalDFA)
Before leaving home:
• Check event health requirements
• Confirm vaccinations with your vet
• Take temperatures for several days before travel
• Pack your own buckets and equipment
• Clean and disinfect the trailer
• Bring a thermometer
• Bring gloves and hand sanitiser
• Plan post-event separation before you leave
At the event
At the showground:
• Avoid nose-to-nose contact
• Do not share buckets
• Do not use communal troughs
• Keep hose nozzles out of buckets
• Do not share grooming tools
• Minimise strangers touching your horse
• Wash hands often
• Keep your horse away from coughing or dull horses
• Take temperatures twice daily at multi-day events
• Report fever or illness early
CDFA event guidance recommends limiting horse-to-horse contact, especially nose-to-nose contact, avoiding shared equipment unless cleaned and disinfected, limiting horse-to-human-to-horse contact, washing hands between horses and avoiding communal water. (CalDFA)
After the event
When your horse returns home:
• Separate from the main herd for at least 14 days where practical
• Monitor temperature twice daily
• Watch appetite, manure, water intake and behaviour
• Use separate buckets and tools
• Handle returning horses last
• Clean and disinfect the trailer and gear
• Call your vet if fever, cough, discharge, diarrhea or dullness appears
EDCC recommends at least 14 days of separation and monitoring for new or returning horses, while CDFA recommends isolating returning horses for a minimum of two weeks where possible. (Equine Disease Communication Center)
When Is This an Emergency?
Call your veterinarian immediately if your horse has:
• Fever above 101.5°F or 38.6°C after travel or exposure
• Fever plus nasal discharge
• Fever plus cough
• Thick yellow or green nasal discharge
• Difficulty breathing
• Severe depression
• Neurologic signs
• Wobbliness or hindlimb weakness
• Urine dribbling
• Difficulty standing
• Recumbency
• Severe diarrhea
• Colic signs with fever
• Swollen lymph nodes under the jaw
• Abscess drainage
• Blood from the nose
• Multiple horses on the property with fever or respiratory signs
• Sudden abortion in a pregnant mare
EHV is particularly important because fever may be transient or the only early sign, and neurologic signs can include ataxia, urine retention or dribbling and recumbency.
The clinical rule:
Do not wait for the second horse to get sick before taking the first fever seriously.
What To Do if a Horse Gets Sick at Your Stable
1. Stop movement
Do not move the sick horse through shared areas unless needed for safety or veterinary care.
Do not take other horses off the property until you have spoken with your vet if contagious disease is possible.
2. Isolate the horse
Move the horse to an isolation area if safe.
If you cannot move the horse, create a perimeter around the current stall or paddock.
Use:
• Signage
• Barriers
• Dedicated equipment
• Dedicated handler if possible
• Separate mucking tools
• Separate buckets
• Separate thermometer
3. Call your veterinarian
Give your vet:
• Temperature
• Signs
• Timeline
• Recent travel
• Show or clinic attendance
• New arrivals
• Exposure to sick horses
• Vaccination history
• Number of horses affected
• Whether pregnant mares or foals are on site
4. Take temperatures of exposed horses
Check all potentially exposed horses twice daily.
EDCC recommends listing horses exposed during the previous 14 days, including exposure during travel, events, home facility contact, temporary visitors, lessons, training and common areas. (Equine Disease Communication Center)
5. Stop sharing equipment
Immediately stop sharing:
• Buckets
• Feed tubs
• Grooming tools
• Tack
• Thermometers
• Muck forks
• Wheelbarrows
• Hoses
• Rugs
• Halters and lead ropes
6. Communicate clearly
Tell owners, riders, staff, farriers, dentists, bodyworkers and visitors what is happening.
Do not hide a suspected outbreak. Quiet outbreaks spread beautifully. Loud, organised biosecurity is far less convenient for germs.
What Else Can Look Like Contagious Disease?
Not every fever, cough or dull horse has a contagious disease.
Important rule-outs include:
• Heat stress
• Transport fatigue
• Dehydration
• Colic
• Hoof abscess
• Cellulitis
• Choke
• Dust irritation
• Allergic airway disease
• Recent vaccination reaction
• Pain or injury
• Dental disease
• Gastric ulcers
• Pneumonia
• Toxin exposure
• Hendra virus in relevant Australian regions
This is why the answer is not to panic. The answer is to isolate first, then let your veterinarian sort the likely cause.
A horse with fever and cough after a show may have influenza, EHV, strangles or another respiratory disease.
A horse with fever and diarrhea may have equine coronavirus, Salmonella, clostridial disease or another gastrointestinal problem.
A horse with fever and wobbliness may need urgent investigation for EHV, West Nile virus, trauma, EPM, toxicity or other neurologic disease.
The biosecurity response protects the group while the diagnosis catches up.
How To Clean and Disinfect Properly
Disinfectant does not work properly through manure, dirt, bedding, mucus and feed residue.
CDFA recommends a four-step process: remove organic matter, wash with soap and water, allow surfaces to dry, then apply disinfectant according to label directions with appropriate contact time. It also notes that alcohol and bleach can be inactivated by organic matter such as soil and manure. (CalDFA)
The correct order is:
-
Remove manure, bedding, hair, dirt and feed residue
-
Wash with detergent and water
-
Rinse and allow to dry
-
Apply the correct disinfectant for the correct contact time
Clean and disinfect:
• Stalls
• Buckets
• Feed tubs
• Waterers
• Grooming tools
• Trailer floors and walls
• Mats
• Stable doors
• Gate latches
• Wash bays
• Thermometers
• Muck tools
• Wheelbarrow handles
• Boots and protective clothing where needed
Do not pressure wash contaminated areas during a suspected outbreak unless your vet advises it is safe. EDCC warns that pressure washers can aerosolise certain viruses. (Equine Disease Communication Center)
Spraying disinfectant over a dirty stable is not biosecurity.
It is a scented motivational poster for bacteria.
Stable Biosecurity Policy: What Every Barn Should Have
Every boarding barn, breeding farm, show stable and lesson facility should have a written disease prevention plan.
A practical policy should include:
• Vaccination requirements
• New arrival quarantine rules
• Returning horse monitoring rules
• Fever reporting threshold
• Sick horse isolation area
• Dedicated isolation equipment
• Staff contact list
• Veterinarian contact details
• State or regional disease reporting contacts
• Cleaning and disinfection protocol
• Visitor rules
• Event travel rules
• Temperature log system
• Communication plan for owners
AAEP recommends developing biosecurity plans before an urgent issue occurs, rather than waiting until an outbreak has already started. (AAEP)
This matters because during an outbreak, everyone suddenly has opinions.
The farrier has heard something.
The owner has read something.
The group chat has achieved flight.
The barn needs a plan before that moment.
Common Mistakes With Contagious Disease Prevention
Mistake 1: Letting horses touch noses at shows
Nose-to-nose contact is one of the easiest ways to share respiratory pathogens. CDFA specifically recommends limiting horse-to-horse contact, especially nose-to-nose contact, at events. (CalDFA)
Mistake 2: Sharing buckets and water
Shared water sources can spread respiratory and gastrointestinal pathogens. Bring your own buckets and avoid communal troughs.
Mistake 3: Skipping temperature checks
Fever can be the first sign of disease. With EHV, fever may be transient and easy to miss unless temperatures are checked twice daily in at-risk horses.
Mistake 4: Putting returning horses straight back with the herd
A horse can look normal while incubating disease. New and returning horses should be separated and monitored before rejoining the main population. (Equine Disease Communication Center)
Mistake 5: Treating vaccination as complete protection
Vaccines reduce risk and severity for some diseases, but vaccinated horses can still become infected, shed pathogens or develop illness. EHV vaccines, for example, do not eliminate the need for biosecurity and temperature monitoring.
Mistake 6: Disinfecting before cleaning
Organic matter can inactivate disinfectants. Remove manure and dirt first, then wash, dry and disinfect. (CalDFA)
Mistake 7: Hiding illness to avoid disruption
This is the big one.
One horse missing a show is inconvenient.
A barn outbreak is expensive, stressful and avoidable.
Myth vs Reality
| Myth | Reality |
|---|---|
| “My horse is vaccinated, so biosecurity does not matter.” | Vaccines help, but they do not block every infection or stop every outbreak. |
| “A horse with no nasal discharge is not contagious.” | Fever may appear before obvious signs, and some exposed horses may shed before owners notice illness. |
| “Only sick horses spread disease.” | Carrier horses and exposed horses can matter, especially with diseases such as strangles. |
| “Disinfectant spray fixes contaminated gear.” | Disinfectant works best only after organic matter is removed and surfaces are washed and dried. |
| “Two weeks after a show is overkill.” | Many disease incubation periods make post-event monitoring valuable, especially after high-risk exposure. |
| “If one horse gets sick, the damage is already done.” | Early isolation, temperature monitoring and movement control can still prevent wider spread. |
Practical Prevention Plan
At home
• Quarantine new arrivals
• Separate returning horses after events where practical
• Use individual buckets and equipment
• Keep feed and water areas clean
• Wash hands between horse groups
• Maintain vaccination records
• Track fever and illness patterns
• Train staff to report early signs
• Have an isolation area ready
• Keep cleaning supplies available
Before travel
• Do not travel sick horses
• Check event health rules
• Take temperatures before departure
• Pack personal gear
• Clean and disinfect the trailer
• Avoid co-hauling with unknown horses where possible
• Bring your own buckets, feed and water if practical
At events
• Avoid nose-to-nose contact
• Avoid communal water
• Do not share equipment
• Wash hands often
• Limit people touching your horse
• Monitor temperature
• Report illness early
• Keep your horse away from coughing, dull or febrile horses
After returning
• Separate for at least 14 days where practical
• Monitor temperature twice daily
• Watch for cough, discharge, diarrhea, poor appetite or dullness
• Use separate equipment
• Handle returning horses last
• Clean and disinfect trailer and gear
• Call your vet if anything changes
Frequently Asked Questions
Can vaccinated horses still get contagious diseases?
Yes. Vaccines can reduce disease risk, severity and spread, but they do not guarantee complete protection. Biosecurity, quarantine, hygiene and monitoring still matter.
How long should I isolate a horse after a show?
For routine returns, separating and monitoring for at least 14 days is a practical minimum where possible. After known exposure, fever at the event, EHV risk, strangles risk or an active outbreak, your veterinarian may recommend a longer quarantine and specific testing. (Equine Disease Communication Center)
What temperature is a fever in a horse?
A commonly used fever threshold is above 101.5°F or 38.6°C. In exposed horses, temperatures should be taken twice daily, ideally 12 hours apart, before fever-reducing medication and not immediately after exercise. (Equine Disease Communication Center)
Should horses share water at shows?
No. Avoid communal troughs and shared buckets. Use your own water and feed equipment, and do not allow hose nozzles to sit inside bucket water.
What should I do if my horse develops a fever after travel?
Separate the horse from others, take and record the temperature, monitor appetite and manure, stop shared equipment use, and call your veterinarian. Do not give fever-reducing medication before speaking with your vet unless you have been instructed to do so.
The Bottom Line
Contagious disease prevention in horses is not about fear.
It is about discipline.
Most outbreaks do not start with one giant mistake. They start with a few small gaps: a returning horse mixed too soon, a shared bucket, a missed fever, a borrowed grooming brush, a trailer that was never cleaned, or a sick horse that kept moving because nobody wanted to be dramatic.
The best biosecurity plan is simple:
• Keep new and returning horses separate
• Check temperatures
• Use your own equipment
• Avoid nose-to-nose contact
• Wash hands
• Clean before disinfecting
• Isolate sick horses early
• Call your vet before the outbreak gets ahead of you
If your horse is bright, eating, temperature-normal and moving well, keep the routine strong.
If your horse is febrile, coughing, snotty, dull, diarrheic, swollen, neurologic or recently exposed, act early. That is not overreacting. That is how good horse people protect the whole barn.
If you are unsure whether your horse’s fever, cough, nasal discharge, diarrhea, recent travel or exposure risk needs quarantine or urgent care, ASK A VET™ can help you organise the signs, track temperatures and decide when veterinary advice should not wait.