Exercise-induced pulmonary hemorrhage (EIPH), also known as "bleeding" or a "bleeding attack", refers to the presence of blood in the airways of the lung in association with exercise. EIPH is common in horses undertaking intense exercise, but it has also been reported in human athletes, racing camels and racing greyhounds. Horses that experience EIPH may also be referred to as "bleeders" or as having "broken a blood vessel". In the majority of cases, EIPH is not apparent unless an endoscopic examination of the airways is performed following exercise. This is distinguished from other forms of bleeding from the nostrils, called epistaxis. Epidemiology EIPH often occurs in horses that race at high speeds, with the number of affected race horses increasing in proportion to the speed and intensity of the exercise. It may occur in racing Thoroughbreds (flat racing, steeplechasing or jump racing), American Quarter Horses (incidence of 50–75%), Standardbreds (incidence of 40–60%), Arabians, and Appaloosas. EIPH also occurs in eventers, jumpers, polo ponies, endurance horses, draft horses that pull competitively, and horses taking part in Western speed events such as barrel racing, reining and cutting. It is rare in endurance horses or draft breeds. The lowest intensities of exercise which may cause EIPH are intense trotting (40–60% maximal oxygen uptake) and cantering at speeds of . EIPH occurs less frequently in stallions than mares or geldings. Prevalence Approximately 43 to 75% of horses have blood in the trachea and bronchi following a single post-race endoscopic examination. In one study, all horses endoscoped on at least three separate occasions following racing had EIPH at least once. Epistaxis (blood coming from one or both nostrils) is much less common, occurring in 0.25–13% of cases. In a survey of over 220,000 horse starts in UK Flat and National Hunt (jump) racing, 185 cases of epistaxis were identified (0.83 per 1000 starts). Similar frequencies have been reported in Japan (1.5 per 1000 starts) and South Africa (1.65 per 1000 starts), whereas a higher frequency has been reported in Korean (8.4 per 1000 starts). Clinical signs Unless a horse has severe EIPH, with blood present at the nostrils (known as epistaxis), the main sign is usually poor athletic performance; other signs are generally subtle and not easy to detect. Frequent swallowing and coughing in the immediate post-exercise recovery period, and poor appetite post-performance may be suggestive of EIPH. A definitive diagnosis can only be made