Horse owners have a vested interest in their horse's health, as health conditions can directly impact their horse's wellbeing, performance, and longevity. Understanding common horse diseases is crucial for anyone involved in equine care, as early recognition of the symptoms of disease can lead to better outcomes. This article covers 30 of the most common horse diseases in North America, to give horse owners and handlers an overview of their symptoms, causes, treatments, and preventative measures. Whether you own a single horse or manage an entire stable, this comprehensive guide aims to equip you with the knowledge needed to keep your equine companions healthy and thriving.

Fibrotic myopathy is a rare condition in horses characterized by the development of fibrous (scar) tissue within the muscles, typically affecting the inner thigh muscles of one or both hindlimbs. Affected horses develop hindlimb stiffness, a distinctive hoof-slapping gait, mechanical, and reduced flexibility. This can lead to impaired mobility and performance. It primarily manifests in disciplines involving sudden stops and sharp turns, such as cutting, making Quarter horses and other stock breeds more susceptible. These disciplines require rapid changes in direction, placing significant stress on the hindlimb muscles.

Sidewinder Syndrome, also known as sidewinder gait or crab walking, is one of the more perplexing and challenging equine health conditions for horse owners and veterinarians alike. This syndrome is characterized by a distinct sideways drift of the horse's trunk and hind limbs while moving forward, resulting in three distinct hoof tracks instead of the usual two. Affected horses exhibit a range of symptoms from awkward movement and difficulty standing still to severe cases where the horse cannot walk forward at all, often spinning or circling in place.

Horse racing is a thrilling sport, demonstrating the power and speed of equine athletes performing at their absolute best. From the raw speed and acceleration of Quarter Horses, to the impressive staying power of Thoroughbreds, to the jumping ability of National Hunt horses, horse racing has something to offer for every horse enthusiast. However, the extreme forces placed on the horse's body at high speeds makes them susceptible to injury and lameness. Not only do these injuries affect the horse and their welfare, they also have economic impacts on the breeders, trainers, and racetrack officials managing these impressive animals.

Parrot mouth is a common equine dental condition typically identified at birth or shortly after. It is characterized by a pronounced overbite where the upper front teeth protrude beyond the lower row of teeth, causing the upper lip to overlap the lower one. Dental misalignment in cases of parrot mouth is due to anatomical abnormalities in one or both jaws of the affected horse's skull. The underlying causes of this condition are not fully understood at this time. While some degree of dental misalignment is normal and often harmless, severe cases of parrot mouth can impede a horse's ability to bite and chew, leading to issues such as weight loss, injury to the roof of the mouth, and digestive problems.

Hoof health is one of the pillars of overall horse health and well being. There are numerous conditions that can impact the horse's hooves, including quittor. Quittor is an infection in the collateral cartilage of the hoof often resulting from a wound that allows bacteria to invade the internal structures of the foot. If left untreated it can lead to tissue death. This condition can be painful and debilitating for the horse, causing significant lameness and discomfort. Understanding the causes, symptoms, and treatment options for quittor is essential to help maintain the horse's health and performance. Early detection and prompt veterinary care can make a significant difference in the horse's recovery and long-term health. By understanding the anatomical context, risk factors, and preventive measures for quittor, horse owners and caretakers can work to ensure their equines maintain excellent hoof health and quality of life. With thorough understanding and attentive care, many of the risks associated with quittor can be effectively managed or even prevented.

Glanders is one of the oldest diseases known to affect horses. It is a highly contagious and fatal disease that affects horses, donkeys, and mules, caused by the bacterium Burkholderia mallei. It poses a significant zoonotic threat, as it can also infect humans and other animals. ^{[1] [2]} Affected horses typically develop a range of symptoms, including high fever, thick nasal discharge, skin lesions, and respiratory distress. Signs of the disease may vary depending on the type of infection and its severity but collectively indicate a serious and potentially fatal condition. While strict regulations have led to the elimination of glanders in several regions, such as North America, the global travel and importation of horses from other countries continue to pose ongoing risks for reintroducing the disease into previously unaffected areas.

Theiler's disease, also known as equine serum hepatitis, is a viral infection likely caused by equine parvovirus-hepatitis. Horses most commonly develop Theiler's disease after administration of an equine-origin biologic product, such as serum or blood. Theiler's disease causes rapid onset liver failure, with symptoms such as yellowing of the gums and whites of the eyes, colic, fever, and uncoordinated movement. Veterinarians may use a combination of bloodwork, ultrasound, and liver biopsy to identify the cause of liver failure. Treatment is primarily supportive, involving intravenous fluids, sedation, antibiotics, and dietary changes. The prognosis varies, with severely affected horses having a poor to grave prognosis. Less severely affected horses may recover completely.