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Diseases in Horses: Glossary

Drs. Foster & Smith Educational Staff
Riding & Training Terms, Horse 
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Equine Glossary: Horse Disease Terms Equine Glossary: Horse Disease Terms
There is a wealth of jargon used throughout the horse world. This is especially true when discussing equine diseases. Learning this vocabulary allows you to better understand articles, event language, and what trainers, farriers, veterinarians, and other horse owners are saying. The following list of terms, while in no way comprehensive, contains some of the terms used to discuss horse diseases.

Addison's Disease: A disease in which an insufficient amount of corticosteroids are secreted by the adrenal gland; also known as hypoadrenocorticism.

Azoturia: An excessive amount of muscle tissue breakdown. Causes pain, swelling, and a reluctance to move. Also known as tying-up (exercise-induced myositis) and Monday Morning sickness, because the condition most often appears in fit horses that were vigorously exercised following a period of rest. May also result in increased nitrogen in the urine.

Broken Winded: Term used to describe horses having an abnormal breathing pattern due to Chronic Obstructive Pulmonary Disease (COPD). Also known as heaves.

Botulism: A rare disease caused by a neurotoxin produced by the bacterium Clostridium botulinum; it targets the neuromuscular nerve endings; often occurs from eating decayed material that contains the toxin.

Chronic Obstructive Pulmonary Disease: see COPD.

Coggins Test: A blood test for Equine Infectious Anemia (EIA). Horses that test positive may be required by the state of occupancy to be destroyed or permanently quarantined. See also EIA.

Colic: General term describing abdominal pain in the horse. Ranges in severity from mild to life threatening. A veterinarian should always be consulted in case of suspected colic.

Congenital: An abnormal condition that an animal possesses at birth, such as hernia.

COPD: Chronic obstructive pulmonary disease. Brought on by allergies and characterized by abnormal breathing pattern and reduced tolerance to exercise; also known as heaves.

Cracked Heels: Inflammation of the heels, resulting in cracked skin and discharge of pus.

Curb: Thickening of the tendon or ligament below the point of the hock, resulting from a strain.

Cushing's Disease: A disease in which an excessive amount of corticosteroids are secreted by the adrenal gland, representing the most common endocrine disorder of horses.

Degenerative Arthritis: see degenerative joint disease (DJD).

Degenerative Joint Disease (DJD): Term for a group of disorders resulting in progressive deterioration of the articular cartilage of a joint, accompanied by bone proliferation around the joint margins and thickening of the soft tissues of the joint; also called degenerative arthritis.

Disseminated Intravascular Coagulation (DIC): A bleeding disorder characterized by the excessive utilization of blood-clotting factors, due to widespread clotting within blood vessels; the resultant excessive bleeding can cause death. This can occur as a complication in a number of diseases.

Distemper: Highly contagious disease caused by the bacteria Streptococcus equi; also known as Strangles.

Dropped Sole: Downward rotation of toe of coffin bone inside hoof due to chronic founder or laminitis.

Dryland Distemper: Disease, also known as Pigeon Fever, which causes abscesses on the chest and belly.

Eastern Equine Encephalomyelitis (EEE): see equine viral encephalomyelitis.

EIA: see equine infectious anemia.

EPM: Equine Protozoal Myeloencephalitis. Neurological disorder caused by a protozoa that invades the spinal cord, causing a variety of symptoms attributed to nerve damage - stumbling, loss of coordination, muscle atrophy, etc.

EPSM: Equine Polysaccharide Storage Myopathy. Muscle wasting condition seen in Draft horses and other breeds.

Equine Infectious Anemia (EIA): One of the most important viral diseases of horses, caused by a retrovirus; it is a chronic infection resulting in a persistent (lifelong) carrier state with periodic exacerbations of anemic illness; also called swamp fever. See also Coggins test.

Equine Influenza: Highly contagious viral respiratory disease of horses caused by subtypes (A1 and A2) of equine influenza virus. Can be transmitted by aerosol from horse to horse over distances as far as 30 yards (for example, by snorting or coughing).

Equine Monocytic Ehrlichiosis: Bacterial disease, often fatal; also known as Potomac horse fever.

Equine Protozoal Myeloencephalitis: Inflammatory disorder of the brain and spinal cord, caused by a protozoan organism.

Equine Viral Arteritis (EVA): Contagious viral disease of horses causing fever, ocular and respiratory signs, fluid distension or swelling of the limbs, and abortion.

Equine Viral Encephalomyelitis: Viral disease causing inflammation of the brain and spinal cord, caused by eastern Equine Encephalomyelitis (EEE) virus, Western Equine Encephalomyelitis (WEE) virus, or Venezuelan Equine Encephalomyelitis (VEE) virus; also known as sleeping sickness.

Favor: To favor; to limp slightly.

Firing: Treatment in which the skin over a leg injury is burned with a hot iron to produce scar tissue.

Fistulous Withers: Inflammation of the bursa at the height of the withers. May become infected and result in foul-smelling discharge.

Founder: Inflammation of the laminae of the foot, which serve to attach the coffin bone to the hoof wall; also known as laminitis.

Go Short: To take short steps, indicative of lameness.

Grease: Inflammation of the skin at the back of the fetlock and pasterns. Seldom seen now, but does occur in horses pastured on wet grass. Can be likened to diaper or nappy rash in babies.

Heaves: Term used to describe the abnormal breathing pattern seen in horses with Chronic Obstructive Pulmonary Disease (COPD), or broken winded. Also a common name for COPD.

Hives: Allergic reaction characterized by bumps or wheals on the skin. More properly called Urticaria.

HYPP: Hyperkalemic Periodic Paralysis. Genetic muscular disorder causing muscle weakness and tremors, sweating and difficulty in breathing. Can be traced back to the Quarter Horse stallion, Impressive.

Impaction Colic: Colic resulting in blockage of the intestine; can result from excessive consumption of grain or lush pasture, or ingestion of foreign material.

Joint Ill: Disease in foals caused by bacteria that enter the body through the navel, resulting in infection that spreads to the joints and causes inflammation, pain and heat.

Lameness: A defect detected when the animal favors the affected foot when standing. The load on the ailing foot in action is eased and a characteristic bobbing of the head occurs as the affected foot strikes the ground.

Laminitis: Inflammation of the laminae (the inside lining of the hoof) of the foot, which serve to attach the coffin bone to the hoof wall; also known as founder.

Lampas: Swelling of the hard palate in a horse's mouth. Sometimes seen in young horses as they transition to hard feed and grain.

Laryngeal Hemiplegia: Partial paralysis of the larynx causing difficulty in breathing and a characteristic noise, known as roaring as the horse breathes.

Lyme Disease: Disease caused by the spirochetal (corkscrew shaped) bacterium Borrelia burgdorferi. It is most commonly transmitted by the bite of deer ticks.

Lymphangitis: Condition in which the lymphatic system, usually in the hind legs, becomes swollen and painful. Seen in working horses on full feed that have to be confined to their stall for some reason, such as severe weather or illness.

Monday Morning Disease: Common name for Azoturia, or tying-up.

Melanoma: Growth or tumor often seen in gray or white horses. May or may not be malignant.

Navicular Disease: Degeneration of the navicular bone, usually on the back surface where the deep flexor tendon passes over the bone. Causes pain and lameness.

Nerve Block: Diagnostic tool in which the veterinarian progressively blocks the nerves of the hoof and leg in order to determine the seat of a lameness.

Neurectomy: Cutting of nerves supplying sensation to the foot. Also known as de-nerving. Used as a treatment in cases of navicular disease.

Potomac Horse Fever: Bacterial disease, often fatal; also known as equine monocytic ehrlichiosis.

Rabies: Inevitably fatal viral disease, primarily of bats and carnivores, characterized by neurological dysfunction; caused by a rhabdovirus.

Rain Rot: Painful, skin inflammation caused by the Dermatophilus organism, characterized by patches of raised hair and hair loss and crusty exudate.

Rhinopneumonitis: Two distinct viruses, equine herpesvirus type 1 (EHV-1) and equine herpesvirus type 4 (EHV-4), cause two different diseases, both of which are known as rhinopneumonitis. Both cause respiratory tract problems, and EHV-1 may also cause abortion, foal death, and paralysis. Infected horses may be feverish and lethargic as well as lose appetite and experience nasal discharge and a cough. Young horses suffer most from respiratory tract infections and may develop pneumonia secondary to EHV-1.

Ringbone: Disorder characterized by new bone growth adjacent to either the pastern or coffin joints; caused by tearing of the ligaments stabilizing the joint. High ringbone describes bone growth around the pastern joint, while low ringbone describes bone growth around the coffin joint.

Ringworm: Contagious fungal disease characterized by small circular patches in which the hair falls out.

Roaring: Characteristic abnormal noise on inhalation, heard in horses with Laryngeal Hemiplegia.

Rotavirus A: Infectious viral foal diarrhea.

Sand Colic: Colic resulting when horses are fed on the ground in areas where the soil is sandy, or when they develop the vice of eating soil.

Scours: Name given to diarrhea in foals.

Scratches: Scabby, oozing skin inflammation on the back of the pasterns, just above the heel.

Seedy Toe: Separation of the hoof wall from the sensitive laminae, often caused by neglecting the feet. Sometimes accompanies laminitis.

Shivers: Abnormal hind leg gait seen in draft horses in which the horse flexes one or both hind legs and tremors can be seen in the large muscles in the upper leg. Thought to be caused by EPSM.

Sidebone: Ossification of the lateral cartilage on either side of the coffin bone within the hoof.

Sleeping sickness: see equine viral encephalomyelitis.

Spavin: Name given to degenerative arthritis of the lower joints of the hock, characterized by a bony swelling that can be felt on the front and inside of the hock.

Splints: Injury to one or both of the metacarpal or splint bones, which run up the back of the cannon bone. Stress or strain can cause the ligaments attaching these bones to the cannon bone to pull and tear, causing heat, swelling and lameness. Eventually additional bone is laid down on the site of the injury, leaving behind a bony swelling.

Strangles: Extremely important, highly contagious bacterial disease of young horses caused by Streptococcus equi; characterized by inflammation of the throat area, with swelling, inflammation, and abscess formation in the associated lymph nodes; also known as distemper.

Swamp fever: see equine infectious anemia.

Tetanus: Acute, often fatal disease caused by a neurotoxin from the bacterium Clostridium tetani, and characterized by violent muscle spasms and contractions, hyper reflexive responses, and "lockjaw"; horses are highly sensitive to the action of tetanus neurotoxin.

Thrush: Degenerative condition of the frog of the foot, characterized by infection and blackening of the affected area; usually occurs in horses housed under unsanitary conditions.

Tying-Up: A mild form of azoturia (see azoturia).

Urticaria: Allergic reaction characterized by bumps or wheals on the skin. More commonly called hives.

Venezuelan Equine Encephalomyelitis (VEE): see equine viral encephalomyelitis.

West Nile Virus (WNV): Virus that is transmitted principally by various species of mosquitoes and can cause inflammation of the brain and spinal cord (encephalomyelitis).

Western Equine Encephalomyelitis (WEE): see equine viral encephalomyelitis.

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