Acute arsenic toxicosis in five horses.

The study reports on five adult horses that exhibited severe symptoms such as watery diarrhea, excessive salivation, muscle tremors, and ataxia, leading to the death of four within 24 hours and the euthanasia of the fifth. Post-mortem examination and tests suggested a case of arsenic poisoning, potentially from ingesting a grain/powder mixture in their pasture contaminated with arsenic.

Clinical Signs and Death

• The research begins by describing the acute health problems five horses suddenly developed. Symptoms included excessive salivation, watery diarrhea, muscle tremors, ataxia (lack of voluntary muscle control), and depression. These symptoms were severe and rapidly progressing, resulting in the death of four horses within a day and the euthanasia of the fifth within two days.

Necropsy Results

• Necropsy (animal autopsy) was performed on two of the horses. Findings included inflamed gastric mucosa, intestines filled with an unusual green-black watery fluid, and multiple large ulcers throughout the cecum and large colon. These results hinted at a serious condition affecting the horses’ gastrointestinal tract.

Histopathological Findings

• The study reports histopathological changes, or tissue alterations at the microscopic level, that were notable in the cecum and large colon. These changes included the death of mucosal tissue (a layer lining the gut), ulceration (the formation of sores), blood clotting in vessels, degeneration of blood vessels beneath the mucosa, and the presence of different kinds of immune response cells.

Confirmation of Arsenic Toxicosis

• The described symptoms, necropsy results, and histopathological findings led the researchers to suspect arsenic toxicosis, or arsenic poisoning. In search of a potential source, a grain/powder mixture was found in the horses’ pasture. Further tests conducted on the necropsied horses’ liver and kidneys as well as on the grain/powder mixture revealed high quantities of arsenic. This confirmed the suspicion of arsenic poisoning, the source of which was likely the contaminated mixture found in their grazing area.

Possible Cause of Poisoning

• The tests also showed the presence of a less significant amount of lead in the kidneys of the horses. Coupled with the high arsenic levels, this led the researchers to reason that the poisoning might have resulted from consuming lead arsenate or lead arsenite, both of which are arsenic-containing compounds.