This article deals with a particularly insidious and devastating cause of pneumonia in foals: Rhodococcus equi (R equi). If not complicated by sepsis, most causes of foal pneumonia are easily diagnosed have a good prognosis, but not the bacteria R equi. R equi has an insidious onset and by the time something is distinctly wrong, a lot of permanent damage is done to the lungs. For the other types of bacterial pneumonia in foals see, Pneumonia and Bacterial Pneumonia.

Early recognition of this disease is much easier on farms where they have seen this disease recently. For a person who has had no experience with R equi the early signs are easily overlooked. Usually the earliest sign is a cough when beginning exercise. The cough is not always present early on and there are many other reasons your foal may be coughing. In cases where the deworming history is spotty, roundworm migration should be on the list of rule outs. Fever may not be present. As the disease progresses the cough worsens, and breathing difficulties and exercise intolerance begin. At this point depression, inappetence and weight loss may become evident. When advanced you may pick up sounds with a stethoscope consistent with cranio-ventral pneumonia.