Phosphine intoxication following oral exposure of horses to aluminum phosphide-treated feed.

The research article discusses the effects of phosphine intoxication in horses that were exposed to feed treated with aluminum phosphide. The exposure resulted in clinical signs including sweating, tachycardia, and ataxia among others, and led to a high fatality rate among the affected horses despite various treatments used.

Exposure to Phosphine

• The study mentions that a total of 66 horses were potentially exposed to phosphine gas around 14 hours after consuming feed that had been treated with aluminum phosphide. This compound, commonly used as a fumigant to eradicate weevils and other pests from grains, can pose health risks to livestock when not handled correctly.

Clinical Signs and Laboratory Findings

• Among the exposed horses, 28 exhibited clear clinical signs of phosphine toxicosis which included profuse sweating, rapid heart rate (tachycardia), rapid breathing (tachypnea), fever (pyrexia), loss of full control of body movements (ataxia), seizures, and widespread muscle tremors.
• Key laboratory findings included abnormally low blood sugar (hypoglycemia) and high plasma concentrations of lactate and ammonia, indicative of metabolic dysfunction. Enzyme activities of gamma-glutamyl transpeptidase, aspartate aminotransferase, and alkaline phosphatase were also heightened, suggesting the occurrence of liver damage.
• Notably, at least 4 horses showed signs of hepatic encephalopathy, a serious condition that occurs when the liver is unable to remove toxins from the blood, causing them to build up and damage the brain.

Necropsy Findings and Detection of Phosphine

• Post-mortem examinations revealed petechial and ecchymotic hemorrhages in multiple organs, widespread vascular congestion, fatty liver disease (hepatic lipidosis), and neuronal cell death (necrosis) in the brain.
• Phosphine was detected in the stomachs of the 3 horses tested, confirming ingestion of the toxic compound.

Treatment and Outcomes

• On the farm, horses were treated with a variety of measures including gastric lavage (stomach washing), administration of di-tri-octahedral smectite (a type of clay used to bind and remove toxins), atropine, fluids, and sedatives. Six horses were hospitalized and given intravenous fluids and nonsteroidal anti-inflammatory drugs.
• Despite these interventions, 27 of the affected horses died within 2 days after exposure. The rapid progress of clinical signs left few treatment options and led to a high fatality rate among the cases.
• Only two surviving horses, including one which showed no clinical signs of phosphine toxicosis, made a full recovery.

Conclusions

• The study concludes with a reminder of the typically minimal risk to livestock when aluminum phosphide fumigation is carried out with appropriate safety precautions.