Common Diseases and Infirmities in Horses

Owning a horse, whether for work or casual riding, can be a source of joy and pride. But it also comes with the responsibility to provide proper care for these majestic animals. 


It’s crucial that horse owners recognize horse diseases and sicknesses that can make a horse ill, or even prove fatal. Wise owners learn about these threats, recognize symptoms, and know how to effectively treat horse sickness. Here are some of the most common horse diseases to watch for in order to keep your horse healthy and happy. 

Equine Colic

Colic is a common digestive disorder in horses. The term includes a series of conditions which cause varying degrees of abdominal pain. 

Symptoms of Equine Colic

  • Biting or kicking motions at the flank or belly
  • Laying down or rolling on the ground
  • Pawing at the ground
  • Anxiety
  • Bloating
  • Loss of interest in food and water
  • Abnormally high pulse rate
  • Inability to defecate

Causes of Equine Colic

Colic in horses may be caused by moldy or tainted food, an abrupt change in feed, sand ingestion, dehydration, high grain-based diets (low forage diets), parasite infestation, stress, or dental problems. 

Treatment of Equine Colic

It’s important to determine the cause of the colic first, in order to correct it. Treatment may require simply changing the diet, but for short-term comfort, many cases can be treated with medication. If there is an impaction or displacement, surgery may be required.

Cushing’s Disease

Cushing’s Disease is a dysfunction of the pituitary gland, and is also known as Pituitary Pars Intermedia Dysfunction (PPID). 

Symptoms of Cushing’s Disease

  • Hypertrichosis (long, curly hair)
  • Delayed haircoat shedding
  • Decreased athletic performance
  • Lethargy
  • Abnormal sweating
  • Laminitis
  • Weight loss
  • Change in body shape (large fat deposits along the mane, muscle wasting, or rounded abdomen or “potbelly”)
  • Increased drinking and urination
  • Prone to infection

Causes of Cushing’s Disease

Cushing’s Disease in horses occurs when a tumor develops in the pituitary gland. 

Treatment of Cushing’s Disease

There is no definitive treatment for horses with Cushing’s Disease, but there are ways to manage and control it, through medication and other practices. Regular farrier visits can prevent laminitis, careful diet management will help combat weight issues, and careful cleaning of any and all wounds can help guard against infection.

Equine Herpesvirus (EHV)/Rhinophneumonitis

Equine Herpesvirus (EHV) is a highly contagious family of viruses that cause respiratory infections, paralysis, abortions, and occasionally death in young horses. Vaccinations are available; contact your veterinarian to see which vaccines are recommended for your horse.

Symptoms of EHV

  • Fever
  • Nasal discharge
  • Incoordination
  • Hind limb weakness
  • Loss of tail tone
  • Lethargy
  • Head tilt
  • Urine dribbling
  • Leaning against a fence or wall to maintain balance
  • Inability to rise
  • Abortion in pregnant mares

Causes of EHV

EHV in horses is caused by several equine herpes viruses. It is spread through contact with infected horses and items contaminated by contact with the virus such as feed, equipment, water utensils, etc. 

Treatment of EHV

Treatment of Equine Herpesvirus involves isolating the affected horse first, then may include anti-inflammatory drugs and intravenous fluids when needed. 

Equine Influenza (Flu)

Equine influenza is a highly contagious infectious disease that is one of the most common horse respiratory conditions. It is endemic in many countries, including in the US, and circulates continuously in the horse population. 

Symptoms of Equine Influenza

  • Fever
  • Nasal discharge (may start clear and progress to thick, green-yellow)
  • Lethargy
  • Loss of appetite
  • Harsh, dry cough

Causes of Equine Influenza

The flu in horses is caused by a virus contracted through direct contact with an infected horse, or indirectly through exposure to a contaminated environment. It is often spread through coughing.

Treatment of Equine Influenza

A vaccine is available, but if a horse does contract the disease, treatment includes rest and supportive care. Treatment may also involve anti-inflammatory medication or antibiotics for persistent fevers or pneumonia that may develop. 

Lyme Disease

Lyme Disease is a bacterial infection spread by the deer tick, which is more prevalent in New England and the surrounding states. 

Symptoms of Lyme Disease

  • Lameness
  • Swollen joints or arthritis
  • Stiffness
  • Muscle atrophy
  • Chronic weight loss
  • Lethargy 
  • Eye inflammation
  • Hypersensitivity to being touched
  • Behavior changes
  • Dermatitis

Causes of Lyme Disease

Lyme Disease is transmitted through the bite of an infected tick. 

Treatment of Lyme Disease

Lyme Disease in horses is typically treated with the tetracycline family of antibiotics. However, these medications may not completely eliminate the bacteria from the body, which may result in a chronic condition that requires lengthier treatment.

Pigeon Fever

Pigeon Fever, also known as Dryland Distemper, causes severe swelling in the chest or abdomen due to bacterial toxins, which gives horses a pigeon-chest appearance.

Symptoms of Pigeon Fever

  • External abscesses along the body, head, limbs, or trunk
  • Internal abscesses 
  • Swelling in the chest or abdomen
  • Mild fever
  • Lethargy
  • Loss of appetite
  • Colic
  • Coughing

Causes of Pigeon Fever

The Corynebacterium pseudotuberculosis bacteria that causes Pigeon Fever is found in the soil, especially in hot, dry climates. Horses are infected by the bites of contaminated flies or contact with the discharge from other sources (bedding, water buckets, human hands or shoes, etc.).

Treatment of Pigeon Fever

It’s best to involve your vet if you suspect your horse has Pigeon Fever. Treatment might include lancing and draining abscesses, daily cleaning and flushing of abscesses, and anti-inflammatory or antibiotic medications. 


Strangles

Strangles is an infectious, contagious disease that affects the upper respiratory tract of a horse. The name stems from common symptoms of lung congestion and difficulty swallowing or breathing, which “strangles” the horse.

Symptoms of Strangles

  • Fever 
  • Yellow nasal discharge
  • Enlarged lymph nodes below the lower jaw that often form abscesses
  • Loss of appetite
  • Difficulty swallowing

Causes of Strangles

Strangles disease is caused by the Streptococcus equi (S. equi) bacteria, which can survive in water sources for over a month. The primary source of the infection is most likely carrier horses that can infect others.

Treatment of Strangles

Immediate veterinary advice and care should be sought for treatment of infected horses and to prevent the spread of the disease. Horses with Strangles are usually isolated for several weeks. Treatment may include anti-inflammatory medication, warm compresses, and flushing burst abscesses. 

Tetanus (Lockjaw)

Tetanus, often called lockjaw, is a disease caused by toxins in a contaminated wound. Tetanus in horses proves deadly in 50-75% of cases, but there is a readily available vaccine to prevent it.

Symptoms of Tetanus

  • Muscular stiffness and spasms
  • Tail often held straight out
  • Difficulty moving and eating
  • Sweating
  • In advanced cases, the horse will collapse with spasms, convulsions, and finally death

Causes of Tetanus

This disease is caused by toxins produced by the Clostridium tetani bacteria found in soil and manure. Infection is usually a case of wound contamination. 

Treatment of Tetanus

Treatment is essential and involves intensive care. This may include identifying and cleaning the infected wound, antimicrobial therapy, sedatives or muscle relaxants, and if needed, an IV for fluids. 

West Nile Virus

West Nile Virus is a mosquito-borne viral disease that can cause inflammation of the brain or the lining of the brain and spinal cord. 

Symptoms of West Nile Virus 

Some infected horses may not exhibit any symptoms at all, while others may show a combination of the following:

  • Stumbling
  • Weak limbs
  • Muscle twitching 
  • Flu-like signs
  • Propulsive walking (moving forward, often without control)
  • Partial paralysis
  • In some cases, death

Causes of West Nile Virus

West Nile Virus in horses is transmitted through mosquitoes that have fed on infected animals, typically birds, and then bite a horse, passing along the virus. 

Treatment of West Nile Virus

It is highly recommended to vaccinate horses annually against West Nile Virus. Horses may require an IV to get sufficient fluids, or intravenous feeding. Slinging may be recommended for horses who are unable to rise, and often head and leg protection are also needed. 

White Line Disease

White Line Disease—also called hollow foot, stall rot, wall thrush, or seedy toe—is an infection in the white line of the hoof, which causes separation of the layers of the hoof wall.

Symptoms of White Line Disease

  • Crumbly or powdery white or gray tissue at the white line
  • Separation of the hoof wall
  • Slowed growth of the hoof wall
  • Bulges or sunken areas of the hoof
  • Warmth in the foot
  • A hollow sound when tapping at the outside wall of the affected area
  • Pain
  • Lameness (severe cases)

Causes of White Line Disease

White Line Disease is caused by a fungus or bacteria that gets in a weakened or compromised hoof wall and causes infection. 

Treatment of White Line Disease

To effectively treat White Line Disease in horses, consult with both a veterinarian and farrier. Treatment usually involves removing the infected tissue, applying antibacterial or antifungal product, and enacting measures to encourage new horn growth.



Even when a serious horse disease or sickness isn’t involved, part of daily horse care is making sure your horse is comfortable. Check out Equiderma’s full line of all-natural skin care products to take care of common skin conditions, and keep your horse looking and feeling its best.

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