Experimental poisoning of horses and cattle with Swainsona canescens var horniana.

This research investigated the impact of Swainsona canescens var horniana, a toxic plant, on horses and cattle. They found that prolonged consumption led to health deterioration and neurological problems, though withdrawal led to normalcy amongst cattle. The study also noted changes in enzyme levels, suggesting potential diagnostic indicators.

Methodology and Observations

• The horses and cattle were exposed to a diet of Swainsona canescens var horniana, a toxic plant species, for 8 to 10 weeks. These animals started showing disturbing signs including losing their physical condition, exhibiting incoordination, and hypersensitivity.
• Post-mortem histological examinations of the tissues of the affected animals revealed the widespread occurrence of cellular vacuolation and the formation of axonal spheroids in the Central Nervous System (CNS). The former is a condition wherein empty spaces or vacuoles appear within a cell, usually indicative of cellular damage or death. The latter is a neurodegenerative change where the axons form abnormal spherical structures, which ultimately disrupts normal neural functions.

Recovery Among Cattle

• The researchers observed that cattle which were removed from the toxic plant diet after being subjected to it for around 8 weeks showed signs of recovery and returned to their normal state.

Biochemical Changes and Potential Diagnosis

• The study reported significant changes in the enzymatic activity of the tested animals. The activity of alpha-mannosidase declined drastically in cattle, whereas in horses, this activity increased over the test period. Alpha-mannosidase is an enzyme which plays a vital role in the modulation of genetic expression in cells, hence any significant alteration in its activity could potentially manifest as pathological changes.
• There was also a significant increase in serum alkaline phosphatase levels in cattle, but no such change was noticed in horses. Alkaline phosphatase serves several important functions, most notably in bone mineralization and liver function, and changes could again indicate underlying physiological disturbances.
• Additionally, it was noticed that the disease symptoms in horses bore similarities to those seen in Indigofera linnaei poisoning (Birdsville disease). However, the differential diagnosis could be made by botanical observations and by noting an increased frequency of vacuolated lymphocytes in the blood (indicative of Swainsona poisoning).