Lysosomal storage disease in Sida carpinifolia toxicosis: an induced mannosidosis in horses.

This research examines a newly recognized neurological disease among ponies in southern Brazil, suspected to be triggered by the ingestion of local plant Sida carpinifolia and suggesting it to be an acquired form of lysosomal storage disease. Pathological observations and comparisons with similar toxicosis suggest that this specific plant should be considered when diagnosing equine neurological disorders.

Objective and Methods

• The study was carried out after three ponies died on a farm. These ponies, along with others, were heavily monitored after having been introduced to a new pasture abundant with Sida carpinifolia.
• Epidemiological data and the clinical findings were carefully recorded. They also collected and examined fragments of multiple organs from the ponies, including elements of their central nervous system (CNS).
• These samples were fixed in neutral formalin and embedded in paraffin-wax, then stained with haematoxylin and eosin.
• Sections of the cerebellum and trigeminal ganglia were submitted to lectin histochemical procedures to further understand the nature of the observed disease.

Results

• The studied ponies displayed notable neurological disturbances such as a rigid gait, muscle tremors, and abdominal pain prior to death. These symptoms began 15-20 days after the ponies were introduced to the Sida carpinifolia infested pasture.
• Pieces of various organs did not show any significant visible lesions. However, microscopic examination of multiple tissues revealed swelling and vacuolation in neurons across the brain, cerebellum, spinal cord, and ganglia.
• Similar degenerative changes were observed in kidney cells, specifically their proximal convoluted tubules.
• Upon using lectin histochemistry, the vacuoles in different cerebellar and ganglion cells displayed strong reactions to particular lectins – these findings lined up with reports on both swainsonine toxicosis and inherited mannosidosis.

Conclusions

• Given the pattern of staining and the histopathological changes, the research suggests a strong link between the ingestion of Sida carpinifolia and the development of this particular neurological disorder.
• The observed disease appears to be a form of acquired lysosomal storage disease, bearing resemblance to Swainsona, Oxytropis and Astragalus toxicosis. These findings recommend Sida carpinifolia be considered during the diagnosis of equine neuropathies.