Exercise Induced Pulmonary Hemorrhage - EIPH in Horses

EIPH in Horses

EIPH has been reported to occur in a variety of race horse breeds including racing Thoroughbreds (both racing on the flat and over jumps), American Quarter Horses (incidence of 50-75%), Standardbreds (incidence of 40-60%), Arabians, and Appaloosas. EIPH has also been reported in eventers, jumpers, polo ponies, endurance horses, draft horses that pull competitively, and horses taking part in Western speed events such as reining, cutting and barrel racing. EIPH is now considered to be an inevitable consequence of moderate to intense exercise in horses and other athletic animals. The lowest intensities of exercise which have been reported to cause EIPH are intense trotting (40-60% maximal oxygen uptake) and cantering at speeds of 16–19 miles per hour (26–31 km/h).

It occurs less frequently in stallions than mares or geldings, but it is associated with airway inflammation and increasing age.

The affliction occurs when blood enters the air passages of a horse's lung, due to fractured lung capillaries. Blood is sometimes evident discharging from a horse's nostrils (epistaxis), however, epitaxis usually only occurs in 5% of bleeders. If a horse does not exhibit epistaxis but is suspected to have EIPH, an endoscopic exam is performed soon after the horse is exercised.