Twenty-eight horses in southern Mozambique died after exhibiting severe respiratory distress. At necropsy, the
overinflated lungs did not collapse, had prominent rib impressions, and were fibrotic and emphysematous. Microscopically,
prominent proliferation of nonciliated epithelial (Clara) cells in the terminal bronchioles and pulmonary fibrosis were observed,
indicative of chronic pneumotoxicity. Transmission electron microscopy demonstrated hyperplasia, desquamation, and apical
bulging of Clara cells into the bronchiolar lumen. The outbreak was attributed to ingestion of Crotalaria dura J.M. Wood
& M.S. Evans subsp. mozambica Polhill and Crotalaria monteiroi Taub. ex Baker f. var. monteiroi. Semiquantitative gas
chromatography–mass spectrometry revealed the presence of pyrrolizidine alkaloids in these 2 Crotalaria species.