Last updated: December 20, 2022
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Two of our neighbor’s horses contracted a common skin disease, and we also had a couple of others in the area develop colic. The prevalence of particular sicknesses made me want to learn more about the most common horse diseases, so I researched the topic.
The most common horse diseases are strangles, equine herpesvirus, colic, heaves, laminitis, and equine influenza, in no particular order. Common equine diseases are viral, bacterial, and parasitic. Note that it’s difficult to state with confidence disease frequency.
New horse owners often think you throw a saddle on and ride. But there is a lot you need to know about horses and familiarity with common horse diseases; their signs and treatments are critical.
Common horse diseases
Horse owners need to be familiar with common horse diseases for the well-being of their animals. Failure to have basic knowledge of equine diseases and their causes can lead to tragic results for your horse.
Not only is this hurtful for the animal, but it also limits your ability to enjoy spending time riding your horses. Horses are susceptible to many diseases that can be avoided with vaccinations and proper care.
I’ll address the most common horse diseases, their causes, and symptoms and advise you on steps to keep your horse protected against these ailments. However, even with the best care, some horses still get sick, just like we do.
Below is an educational Youtube video that covers diseases in horses and the vaccinations available.
Strangles (Streptococcus equi)
Strangles is a big problem in the global equine population and is the most frequently diagnosed infectious disease. Strangles is a bacterial infection of the lymph nodes in a horse’s throat.
The infected lymph nodes swell and burst. When the infected nodes burst, they release puss that drains out of the horse’s nose and beneath its jaws. The swelling and bursting lymph glands choke the infected horse; thus, the name strangles.
Streptococcus Equi is the bacteria that causes the disease and is easily transmitted between horses. The bacteria survive outside the animal’s body and live for days in a barn and on the tack.
It’s typically spread through horse farms in shared water sources and tack. Streptococcus Equi is one hardy bacteria that has been around for centuries.
Symptoms of Strangles.
Strangles are a bacterial infection that causes an infected horse’s lymph nodes to develop abscesses that swell and burst, discharging a thick yellowish-green mucous snot.
The symptoms of infected horses include fever, mucous discharge, depression, lethargy, coughing, decreased appetite, and difficulty swallowing.
Strangles isn’t typically fatal; however, horses with nervous system infection from strangles have died in extreme cases.
Prevention of strangles.
Strangles is one of the most common horse diseases in the world because it’s tough to defeat. The condition has been around as far back as the thirteenth century.
There are vaccines for the disease, but most have adverse side effects that make their use questionable. However, science is regularly developing new and better vaccines, so check with your vet for the latest news.
The best way to prevent the disease is through rigorous testing and isolation of infected horses and equipment. If you have a horse test positive, clean everything, and quarantine the infected animal.
To be effective, you have to be thorough; remember this bacteria is strong and can survive outside and in extreme temperatures. Wash all your clothes and any equipment the horse contacted. Good hygiene will help prevent the spread of the disease to other animals on your farm.
Treatment for strangles
Treatment may include getting the pus out of the lymph glands with a scope and then treating it with a topical antibiotic. However, before this is necessary, veterinarians often prescribe horses anti-inflammatory medication to reduce fever and make them feel good enough to start eating again.
Hot compresses on the lymph glands and feeding moist food on the floor also help the abscesses drain and rupture. Occasionally vets prescribe a course of antibiotics.
Equine herpesvirus-4 is the most common equine virus in the world and one of the most common horse diseases globally. It typically causes respiratory ailments and occasionally abortion or neurologic disorders.
Another common herpesvirus strain is the herpesvirus-1, which causes respiratory illness and abortion, and neurologic diseases. Both strains are most commonly seen in weanlings and yearlings.
It is also believed that older horses often are carriers but don’t exhibit symptoms of infection. After a horse is exposed to the virus, the incubation period can be as short as twenty-four hours but is typically four to six days or longer.
It is most commonly transmitted when horses inhale the disease coughed into the air by infected horses.
Symptoms of equine herpesvirus infection.
Symptoms of the more common equine herpesvirus-4 include fever, coughing, nasal discharge, enlarged lymph nodes, lethargy, weight loss, and eye infections, such as conjunctivitis and keratitis.
Prevention of equine herpesvirus infection.
To prevent the spread of equine herpesvirus:
- Keep infected horses isolated.
- Do not share tack, and disinfect all common areas.
- Use hand sanitizers after you’ve been exposed to an infected horse.
There are vaccines for certain strains of herpesvirus, but these seem to help prevent the disease’s spread more than prevent a horse from contracting it. There are no vaccines I’m aware of that protect a horse against all strains of equine herpesvirus.
Treatment for equine herpesvirus infection.
Your horse can be tested with a nasal swap to confirm it has an equine herpesvirus infection. But what treatment options are available once it has the disease?
Treatment typically involves medication to reduce fever and coughing and maybe a cycle of antibiotics to prevent secondary infection. Otherwise, the respiratory disease has to run its course.
If the animal advances to neurological deficits associated with the disease, a sling may be necessary to keep the horse upright. In extreme cases, food and water are given intravenously.
Of the many common horse diseases, colic is the most deadly of domesticated horses. It’s believed that ten percent of the equine population has contracted colic during its life.
Ten percent is an exceedingly high rate; however, keep in mind that the term “colic” is broadly used to describe various equine stomach ailments.
Some of the common causes of colic are gas, intestinal impaction, overeating grain, sand ingestion, and parasite infection. If you suspect your horse has colic, check its vital signs, keep it on its feet, and call your veterinarian.
Don’t let your horse eat or drink until after you talk to your vet.
Symptoms of equine colic.
Horses with colic behave differently. I’ve seen this firsthand with a couple of horses, one rolled on the ground, and another kicked at its stomach and turned its head back.
Because horses do so many different things when they have colic, it’s challenging to know that your horse is suffering from the disease. Here is a list of the more common symptoms horses display when they have colic:
- Loss of appetite
- Pawing the ground
- Looking back at its flank
- Lying down
- Excessive moving around in an agitated state: getting up and down repeatedly or walking in circles.
- Curling its upper lip
- Kicking at its stomach
- Rolling on the ground
- Increased heart rate
- Bloated belly
- Little or no manure
Prevention of equine colic.
Unlike some of the other common horse diseases, colic is not preventable in many instances, but you can do things to lower your horse’s risk of contracting the disease.
- Have a readily available water source for your horse,
- Turn your horse out as much as practical.
- Don’t feed hay on sandy ground.
- Don’t feed your horse grain unless it needs the extra energy.
- Change your horse’s diet gradually.
- Keep your horse’s teeth floated.
- Have a good insect control program
Treatment for equine colic.
Because colic is a general term, it’s essential to determine the cause and apply the proper treatment. Most types of colic can be treated with medication, but severe colic, such as impactions and intestinal twists, require surgery.
It’s critical to have your horse evaluated by a veterinarian as soon as possible so he can determine the correct course of treatment. The vet can often administer medication or use a tube to relieve gas onsite to treat colic.
Heaves is a chronic pulmonary disease of horses, similar to asthma in humans, but unlike many common horses diseases, it’s non-infectious.
The condition is also referred to by other names, such as recurrent airway obstruction (RAO), chronic obstructive pulmonary disease (COPD), broken wind, and emphysema.
Horses with heaves have an allergic reaction to inhaled particles, typically molds found in hay and straw. The inhaled particles cause an allergic reaction that constricts the lungs’ airways. Heaves primarily affect horses over six years old.
Once the airways are obstructed, the horse has difficulty drawing in and expelling air from its lungs, limiting its ability to perform basic tasks.
Symptoms of heaves.
Early signs of heaves are occasional coughing, but as the disease worsens, the horse will get winded quickly during exercise and have an increased respiratory rate. The animal will also begin to wheeze, flare its nostrils, and start having nasal discharge.
If the disease is allowed to progress untreated, a horse with heaves will look bloated. The bloated appearance is caused by large stomach muscles’ development from constant overworking needed to draw in air.
Prevention of heaves.
If you must feed hay, then soak or steam it before giving it to your horse to reduce dust. And if your horse is kept in a stall, make sure it’s well-ventilated and as free of dust as possible.
Treatment for heaves.
If you believe your horse is developing, please contact your veterinarian immediately. Although there are no cures, he can reduce the symptoms and prevent the disease from progressing.
Depending on the cause of your horse’s heaves, the vet may prescribe a course of anti-inflammatory medicines. Typically veterinarians administer the drugs orally or by injection.
An aerosol option is also available for horses, much like inhalers used for humans. These have proven affected but require special equipment, and treatments are expensive.
Horses often successfully recover from heaves and live a productive life when their condition is managed correctly, specifically improved air quality.
Laminitis is one of the most common horse diseases of a horse’s hoof. It is an excruciating and often recurrent condition that affects the tissues bonding the hoof wall to the coffin bone (the coffin bone is also known as the pedal bone).
The disease is caused by the disruption of blood flow to the laminae, which secures the coffin bone to the hoof wall. The disorder causes inflammation and weakens the laminae and the bond to the hoof wall.
When the bond is lost, the coffin bone may rotate within the horse’s foot, sink and exit the sole of the animal’s foot. Laminitis most often affects the front feet. “Laminitis” and “founder” are used interchangeably to describe the condition.
Symptoms of laminitis.
Laminitis is a progressive disease that leads to lameness. It is essential to know the early signs so you can catch the disease while it has a chance to recover. If you believe your horse is developing laminitis, contact your veterinarian right away.
Here is a list of common early signs of laminitis:
- Increased digital pulse in the feet. Slide your fingers below the fetlock right above the hoof to check the digital pulse in horses with laminitis; the heartbeat is strong, pounding. Compare it to an unaffected horse to get a baseline.
- Heat in the horses’ feet. When damage occurs in the animal’s foot, it gets hot. If your horse’s hoof remains at elevated temperatures for a long time, over two hours, it could be an early sign of laminitis.
- Unusual rings in the hoof wall. If you notice the hoof rings become wider from toe to heel, this could be a sign of laminitis.
- Increased resting heart rate. You should have a baseline heart rate for your horses; if you notice an increase in its baseline over an extended period, this could indicate laminitis.
- Frequent weight shifting. Horses with early signs of laminitis will shift their weight from side to side at an unusually high rate.
- Widening or blood in the white line. The spot where the hoof wall and sole meet is the white line. If you notice it is wider than usual or blood in the region, it could be caused by laminitis.
- Change in stride. If your horse begins to stride differently, typically taking shorter strides, laminitis could be the cause.
- Pain in the toe of the hoof. Put pressure on the hoof toe with hoof testers; if your horse is sensitive in this region, laminitis might be the cause.
- Leaning back on its heels: Because the laminitis pain is in the toe of the hoof, horses with laminitis often lean back on their heels to reduce pressure on the front of their feet.
Your best chance to prevent lameness and the awful effects of chronic laminitis is to catch the disease in its early stages.
Prevention of laminitis.
Laminitis can be prevented in some cases with proper diet and exercise. Most horses should be on a forage-only diet. Grains and sugars trigger laminitis. Lush pasture grass contains high amounts of sugar and should be avoided by horses prone to laminitis.
Keep your horse’s weight within healthy parameters. Obese horses are prone to develop laminitis. Always make gradual changes to a horse’s diet, and never overfeed your horse.
Horses have fragile digestive systems, and drastic dietary changes will throw off their balance and trigger laminitis. Proper care of your horse’s hooves is essential to keeping laminitis at bay. Imbalanced feet put undue pressure on hoofs and can lead to laminitis.
Treatment for laminitis.
In severe laminitis cases, emergency treatment is needed, but even in mild cases, the sooner treatment begins, the better the chance for recovery. The type of treatment depends on the specifics related to each horse but typically includes:
- Medication: Pain and anti-inflammatory drugs are administered to control the pain. A commonly used anti-inflammatory drug is phenylbutazone. Acepromazine is also widely used to increase blood flow to the feet.
- Ice: Laminitis associated with inflammation can benefit from icing to reduce swelling and cool the feet.
- Dietary restrictions: Discussed above in prevention.
- Mineral oil: Giving a dose of mineral oil helps horses that have gotten into a feed room and overeat.
- Reduce foot pressure. Keep your horse on a soft surface. Hard surfaces such as concrete increase pain and stress. It’s best if the horse lays down to alleviate all foot pressure. Corrective shoeing can also help to reduce pressure on the affected foot.
- Drain abscesses: Abscesses develop inside the horse’s hoof and build pressure. The pressure in the hoof is painful and increases inflammation.
Among the common horse diseases, equine influenza is always near the top each year. This is equine flu, and it’s very contagious. Two primary viral strains cause it, but the most common one is equine influenza A (H3N8), which infects the horse’s respiratory tract.
Equine influenza is transmitted through the air when a horse coughs. Your horse can get it when you visit horse shows, trail rides, or any place horses congregate.
Australia gave the world a prime example of how fast this disease spreads. Before 2007, there were no known cases of equine flu. Then in early August of that year, eight infected horses were imported, and six weeks later, one thousand horses had the disease, and it continued to multiply.
Symptoms of equine influenza.
Common symptoms of equine influenza include lethargy, loss of appetite, fever, nasal discharge, coughing, and swollen lymph glands.
Prevention of equine influenza.
The best prevention is to keep away from strange horses, especially ones with a cough. You should also practice good hygiene and don’t share water sources or grooming equipment with outside horses.
If you suspect one of your horses has equine flu, call your veterinarian immediately so he can test your animal. If your horse tests for the flu, keep it separate from your other animals.
There are two types of equine influenza virus vaccines, inactivated (killed) vaccines for intramuscular administration and modified-live vaccines for intranasal administration.
Vaccines will reduce the chances your horse will get equine influenza, but it’s not guaranteed to prevent your horse from getting the disease.
Treatment for equine influenza.
Your veterinarian is likely to tell you that the flu must run its course and recommend you provide supportive care. This care would likely include keeping your horse in a clean, well-ventilated stall or paddock and ensuring it has access to clean water and plenty of hay.
Your veterinarian may prescribe Banamine to reduce its temperature. Besides treatment for secondary diseases, there isn’t much else you can do but wait for the disease to run its course.
Your horse should be ready to ride a few weeks after it stops coughing.
Equine infectious anemia (EIA)
Equine infection anemia is not one of the most common horse diseases, but it spreads easily and causes such devastation that I thought it prudent to include it in this article.
Equine infectious anemia (EIA) is a viral disease carried in the blood and is primarily transmitted by horse and deer flies. An animal infected with EIA will not immediately display symptoms of the disease.
After infection, diseases that have an incubation period before the disease begins to cause signs of sickness are referred to as lentivirus. Lentiviruses are extremely dangerous because an infected horse will look healthy but can transmit the disease to other horses nearby.
Horses with equine infectious anemia may not display any signs of the disease for up to forty-five days or as early as seven days. Once a horse has EIA, they carry the disease for the rest of their lives.
The Coggins test is used to determine if a horse is infected with EIA. A negative Coggins is required by all States when transporting horses across borders, and most equine facilities also require a Coggins certification when horses are brought there.
Symptoms of Equine infectious anemia.
Horses with equine infectious anemia often have recurrent symptoms of high fever, depression, swelling in the lower legs, and chronic weight loss. You may also notice the yellowing of their eyes.
Acute EIA hits horses hard and fast; they typically have a spike in fever and often die within a couple of weeks. The ones that survive often live with the disease for the rest of their lives.
Horses with chronic EIA live in a cycle of perpetual sickness. They retain fluid, get a fever, and lose weight. These horses are often euthanized to relieve them of the painful effects of the disease.
Some horses are carriers with no noticeable signs of the disease. They can spread it to other animals. This is why a Coggins test is crucial for all horses.
Prevention of equine infectious anemia.
To reduce the risk of contracting EIA, have your horse tested annually, quarantine infected horses, have an effective insect control program, and only participate in public events where Coggins testing is required. These steps help reduce the risk of horses contracting EIA.
Testing horses has significantly reduced EIA in the United States. Before the development of the Coggins test in 1970, equine infectious anemia was widespread.
Even though testing has drastically reduced the disease, it is still found in some horses each year.
Treatment for horses with EIA.
Unfortunately, there aren’t many options for horses that develop this disease. You can either elect to keep your horse isolated from other animals or euthanize it.
These are common horse diseases all horse owners should be familiar with; however, it’s not an exclusive list. There are many more ailments and diseases you should know about as well, such as thrush, rain rot, joint disorders, and equine sleeping disease.
It’s critical that you contact a vet if you have any concerns about your horse’s health. Remember, all horse owners are constantly learning about their animals.
What is the deadliest disease in horses?
Though horses can contract some really bad diseases, the deadliest is likely Equine Infectious Anemia (EIA). It is a highly contagious, often fatal viral disease that affects horses and other equids, including donkeys and mules.
Is equine influenza deadly?
It can be deadly, but most cases are mild, and horses usually recover with rest. Equine influenza is a highly contagious viral respiratory disease affecting horses. Symptoms include fever, coughing, and nasal discharge.
Are ulcers common in horses?
Ulcers can be common in horses, particularly in those that are under stress or have a diet high in grains. Ulcers can occur in the stomach or in the small intestine, and they are caused by the erosion of the lining of these organs.
- What Is a Coggins Test and Why My Horse Needs One? 5 Reasons
- Why Does My Horse Have Diarrhea? Tips to Prevent and Treat
- What is Colic in a Horse? Causes and Symptoms
- What Causes a Horse to Founder?
- Is My Horse Overweight? A Plan to Reduce Weight Safely
- Horses Can’t Vomit, Do You Know Why?
- Why Does My Horse Eat Dirt?
- Is My Horse Dehydrated? 10 Clear Signs of Equine Dehydration
- Why Do Horses Crib (Bite on Wood)? The Answer isn’t Simple
- The Very Best Grazing Muzzles, and Why Your Horse Needs One
Meet Miles Henry
An avid equestrian and seasoned racehorse owner, Miles Henry brings his extensive experience to the equine world, proudly associating with the AQHA, The Jockey Club, and various other equine organizations. Beyond the racetrack, Miles is an accomplished author, having published various books about horses, and is a recognized authority in the field, with his work cited in multiple publications.
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