Equine Anhidrosis Study Guide

Overview and Clinical Importance

Anhidrosis (also known as dry coat syndrome or non-sweating disease) is a thermoregulatory disorder characterized by the decreased or complete inability to sweat in response to appropriate stimuli such as exercise or elevated ambient temperature. This condition primarily affects horses living in hot, humid climates and represents a significant performance-limiting and potentially life-threatening condition in equine practice.

Horses rely on sweating as their primary mechanism for thermoregulation, with 65-70% of excess body heat dissipated through sweat evaporation. The equine skin contains approximately 810 sweat glands per square centimeter, making horses exceptional sweaters among domestic animals. When this cooling mechanism fails, affected horses are at severe risk of hyperthermia, heat stroke, and death.

Etiology and Pathophysiology

Normal Equine Sweat Physiology

Equine sweat glands are primarily of the apocrine type, associated with hair follicles throughout the body. Sweating is controlled by both neural and humoral mechanisms through beta-2 adrenergic receptors on sweat gland secretory cells. Circulating epinephrine released during exercise and stress, along with direct neural release of norepinephrine from adrenergic nerve endings, stimulates these receptors to initiate sweat production.