Respiratory Distress in Young Foals

Bronchointerstitial pneumonia is one of the most common causes of respiratory distress in foals. It is a sporadic, rapidly progressive disease characterized by acute respiratory distress and high mortality in foals between one week and eight months of age. Other causes of respiratory distress are viral or bacterial pneumonia, chest trauma, heart defects, and allergic reactions to vaccines.

Bronchointerstitial tells us that the disease affects the airways (bronchi) and the interconnecting tissue (interstitial) of the lungs. The fact that both areas are damaged is the reason that foals go into distress.

Bronchointerstitial pneumonia causes respiratory distress by filling air sacs that normally exchange oxygen and carbon dioxide with fluid and damaged cells. The air sacs are rendered useless. The lung goes from spongy and air-filled to a rubbery and fluid filled. The damaged lungs try desperately to inhale and exhale, but the heavy lungs are too stiff, and the airsacs no longer allow oxygen to diffuse into the blood stream. Consequently, the entire body becomes deprived of oxygen.

Foals present with a history of sudden onset of respiratory distress, high fever, coughing, and nasal discharge.

No one cause of bronchointerstitial pneumonia has been identified. It is most likely that bronchointerstitial pneumonia is actually a rogue inflammatory response of the lung to varying insults. Researchers suspect that diseases such as Rhodococcus equi, a serious cause of bacterial pneumonia in foals of this age group, or Pneumocystis carinii, a more rare fungal cause of pneumonia in people and horses whose immune systems are depressed, may be the underlying triggers of bronchointerstitial pneumonia.

A common factor in many cases of bronchointerstitial pneumonia is the use of erythromycin, an antibiotic that is invaluable in the treatment of Rhodococcus equi. Erythromycin might suppress the lung's ability to mount an immune response, thus allowing 'oddball' infections, such as Pneumocystis carinii, to become established in the lung. Also, erythromycin has been shown to cause primary hyperthermia (overheating) in a small subset of foals.

Researchers speculate that bronchointerstitial pneumonia may be complicated by hyperthermia in some cases – in essence, the signs of distress in bronchointerstitial pneumonia may be due to thermal injury to the lung, or hyperthermic effects on the body.

This type of pneumonia is generally seen on farms where there are multiple mares and foals, so there may be a stress or infectious cause that is more likely to appear on breeding farms. Yet another potential cause of bronchointerstitial pneumonia is plant toxins, although none have been conclusively identified as yet.

Death rates from bronchointerstitial pneumonia are high. It progresses rapidly, and is often refractory to treatment.

Watch to Watch For



Home Care and Prevention

Be vigilant in making sure that foals do not become overheated. If you must transport a foal during hot weather, do so at night, or in the cool of the early morning. If you must travel during the day, make sure that you have excellent ventilation, and make frequent stops to have the foal drink water and/or nurse. Make liberal use of water to wash the foal down every 1/2 hour or so.

Be especially vigilant if you have a foal that is being treated with erythromycin. Keep an eagle eye on all young foals to make sure that you don't miss subclinical lung disease. Remember, a cough and a snotty nose may be common in this age group, but it is not normal and should not be tolerated for any length of time.