Aspiration pneumonia is an infection of the lungs caused by inhalation of a foreign substance. It is more common in foals, but can be seen in horses of any age.
Anaplasmosis is an infectious, tick-borne disease that affects horses caused by the bacteria Anaplasma phagocytophilum.
African horse sickness (AHS) is a highly fatal disease endemic to sub-Saharan Africa.
Anterior enteritis (AE), also known as proximal enteritis, is inflammation of the first two parts of the small intestine - the duodenum and the jejunum. The cause of AE in horses is suspected to be clostridial infection, although currently causes are not completely understood.
Osteoarthritis is a progressive disease resulting in damage to the joint cartilage and underlying bone. Arthritic damage causes significant pain, and typically results in lameness, limited mobility, joint swelling, and poor performance.
Aflatoxins are a group of fungal toxins produced by *Aspergillus* fungi, which grows on a number of feed crops, such as corn, peanuts, and soybeans.
Alsike clover toxicosis is a potentially life-threatening condition caused in horses by the ingestion of the Alsike clover (Trifolium hybridum). Ingestion of Trifolium hybridum can cause two syndromes: liver failure and dew poisoning (Photosensitivity)
Aural plaques in horses are white, round, raised lesions on the inside of the ear caused by a papillomavirus (warts) infection.
Allergies in horses occur when the immune system responds excessively to an allergen, such as mold, pollen, or dust. In horses, the main symptom of allergies is hives on the skin, which may be extremely itchy.
Angular limb deformities (ALD) in foals are deformities of the limbs where the leg is not straight when viewed from the front or behind. This is usually due to one or more joints deviating inward or outward on the affected limb.
Atheromas of the false nostril in horses are non-painful masses that develop into soft to firm mass on the side of the face. It is a congenital condition that becomes more apparent in adulthood as the mass grows.
Atrial fibrillation in horses is a cardiac arrhythmia where the atria (top of the heart) beat rapidly and out of synchronization with the rest of the heart. Causes of atrial fibrillation include heart disease, electrolyte imbalances, and colic.
Anthrax in horses is a rare disease caused by infection with the spore forming bacteria Bacillus anthracis. The disease results following spread of the bacteria throughout the body, and subsequent production of a deadly toxin.
Abnormal molar wear in horses involves uneven grinding of the rear teeth.
Abnormal incisor wear in horses is the uneven shaping of the front teeth, due to excessive or insufficient grinding of the chewing surface.
Adrenal gland cancer (pheochromocytoma; PCC) in horses is a rare form of tumor that arises from the adrenal medulla.