Toxic pneumopathy by Trema micrantha in sheep in the State of Santa Catarina, Brazil

Poisoning by Trema micrantha commonly causes hepatocellular necrosis in cattle, sheep, and goats and edema and cerebral hemorrhage in horses. This plant can cause toxic pneumopathy in sheep, and there is only one report of the natural form and one of the experimental form in the State of Rio Grande do Sul. This study aimed to report an outbreak of the respiratory form of natural poisoning by T. micrantha in sheep. Six sheep developed clinical respiratory signs after consumption of the plant and four of them died and two recovered after treatment with dexamethasone. The sheep presented tachypnea, noisy breathing, edema of the face, eyelids, and vulva, and subcutaneous emphysema on the face and neck. Necropsy (Sheep 2, 3, and 4) showed uncollapsed, heavy, diffuse red lungs with evident costal impressions and a moderate amount of serosanguineous fluid flowed at section. The liver had a moderate diffuse evident lobular pattern. The histopathology of the lungs of the three necropsied sheep showed congestion and edema with the formation of hyaline membranes within accentuated diffuse alveoli, in addition to thickening of the alveolar septa due to mild to moderate diffuse type II pneumocyte hyperplasia and also mild to moderate diffuse infiltrate of macrophages, lymphocytes, plasma cells, and neutrophils in the lumen of alveoli, bronchi, and bronchioles. Sheep 3 also showed type II pneumocytes with enlarged and hyperchromatic nuclei, sometimes binucleated with evident nucleoli, and, in some regions, the pneumocytes were desquamated to the alveolar lumen forming small syncytia and mild multifocal hyperplasia in the bronchial epithelium. The anti-cytokeratin IHC evaluation showed marked diffuse intracytoplasmic staining in hyperplastic type II pneumocytes in the bronchiolar epithelium of the three evaluated sheep. The liver of the three sheep had mild multifocal centrilobular necrosis. It seems to be the second report of spontaneous poisoning by T. micrantha in sheep developing lung lesions described in Brazil and the first in the State of Santa Catarina.