ACUTE HEMORRHAGIC PULMONARY INFARCTION AND NECROTIZING PNEUMONIA IN HORSES - 21 CASES (1967-1993)

Objective-To characterize history, clinical signs, and pathologic find ings in horses with histologically confirmed acute hemorrhagic pulmona ry infarction and necrotizing pneumonia. Design-Retrospective study. A nimals-21 horses. Results-19 of the 21 horses were Thoroughbred raceho rses in training. Eighteen horses had had strenuous exercise immediate ly prior to onset of illness. Fifteen horses had a serosanguineous nas al discharge during hospitalization. Seventeen horses had radiographic evidence of pulmonary consolidation and pleural effusion. Nine of 14 horses had ultrasonographic evidence of large pulmonary parenchymal de fects consistent with consolidation. Pleurocentesis yielded a suppurat ive, serosanguineous effusion in the 14 horses in which it was perform ed. Bacteria were isolated from all transtracheal aspirates (14) and f rom 6 of 12 pleural fluid samples. Actinobacillus suis-like organisms and Streptococcus equi subsp zooepidemicus were most commonly isolated . Nineteen horses were hospitalized and treated. Mean duration of trea tment was 5 days, and most horses were euthanatized because of seconda ry complications, continued costs of medical treatment, or poor progno sis for future performance. Pathologic lesions included well-demarcate d regions of hemorrhagic pulmonary infarction with necrosis and a sero sanguineous pleural effusion. Thrombosis of pulmonary vessels was foun d in 11 horses. Clinical Implications-An acute or peracute onset of se vere respiratory distress, with serosanguineous nasal discharge, ultra sonographic and radiographic evidence of severe pulmonary consolidatio n, and serosanguineous suppurative pleural effusion, is strongly sugge stive of pulmonary infarction in horses. Horses with pulmonary infarct ion responded poorly to conventional treatment for pleuropneumonia and had a poor prognosis for recovery.