Poisoning by Amaranthus spp. (Amaranthaceae) in pigs in Rio Grande do Sul, Brazil

Two outbreaks of Amaranthus spp. poisoning occurring in young pigs in southern Brazil in late summer and early autumn are described. In both instances large amounts of freshly harvested Amaranthus spp. in its seeding stage were fed to the pigs. In one farm. the Amaranthus was identified as A. viridis. Fourteen out of 25 pigs (56%) in one farm and 17 out of 100 (17%) in another died. Clinical signs included anorexia, depression, incoordinated gait; muscle stiffness, lateral recumbency, followed by death which occurred from 4 to 48 hours after clinical signs were observed. Necropsy findings included perirenal edema and edema of other sites such as ascites: hydrotorax, hydropericardium, of the mesentery and the subcutaneous tissue of the ventral abdominal wall. The kidneys were pale and soft with subcapsular petechiae. In one of the three cases submitted for post-mortem examination there was marked edema of the renal papilla. Main histopathological findings were toxic tubular nephrosis affecting mainly the proximal convoluted tubules and mild tubular regeneration. In one case few refringent crystals were seen in the lumina of proximal tubules and in two cases the degenerative renal lesions were associated with moderate mononuclear interstitial inflitrate. Extra-renal lesions consisting of fibrononecrotic glossitis and esophagitis were found in one pig and attributed to uremia.