Symmetric focal degeneration in the cerebellar and vestibular nuclei in swine caused by ingestion of Aeschynomene indica seeds.

A vestibulocerebellar disorder was observed in 2- to 4-month-old swine after consumption of broken rice contaminated with 13% Aeschynomene indica seeds. Affected animals recovered in 2-14 days after removal of the contaminated food. To reproduce the syndrome, 10 pigs were fed 13% A. indica seeds in commercial pig ration or rice. They showed clinical signs similar to those observed in the spontaneous cases, 1 hour to 6 days after ingestion. Three pigs recovered after the withdrawal of the contaminated food. The others were killed. Two pigs that were fed for 25 days with food containing 3% and 6% seeds and two control pigs did not show clinical signs. Histologic lesions were characterized by symmetric focal degeneration in the cerebellar and vestibular nuclei. The initial lesion, observed 24 hours after the first ingestion, was characterized by vacuolation of the neuropil. Subsequently, there was progressive loss of parenchyma, vascular reaction, a few small spheroids, astrocytosis, and accumulation of gitter cells. The brains from four pigs were perfused with a buffered solution of glutaraldehyde-paraformaldehyde 12-48 hours after they started to ingest the seeds. No ultrastructural lesions were observed in the cerebellar nuclei after 12 hours of seed consumption. At 24 hours, endothelial cells and pericytes were separated by empty spaces from astrocyte foot processes, suggesting perivascular edema. The astrocytes were enlarged, consistent with intracellular fluid accumulation. These results suggest that A. indica seeds are toxic, causing functional derangement of the vestibulocerebellar system, followed by alterations in the microvasculature in the cerebellar and vestibular nuclei.