Tansy ragwort poisoning in a horse in southern Ontario.

The research article discusses a case where a horse in Southern Ontario exhibited strange behavior, apparent lameness, and colic due to poisoning from consuming tansy ragwort, a weed rich in pyrrolizidine alkaloids, during a period of drought. The horse’s afflictions were a result of liver failure and hepatoencephalopathy but it recovered fully after being removed from the pasture.

Behavior and Symptoms

• The horse’s unusual behavior and apparent lameness were attributed to the ingestion of tansy ragwort, a weed known to contain harmful toxins. The horse also displayed signs of colic, a common equine condition that refers to abdominal pain, and can range from mild to severe.

Liver Failure and Hepatoencephalopathy

• The horse’s consumption of tansy ragwort led to liver failure and hepatoencephalopathy. Liver failure is a serious condition where the liver stops functioning properly, either partially or completely.
• Hepatoencephalopathy is a condition caused by liver damage, leading to a buildup of toxins in the blood. These toxins can then affect brain function, causing behavioral changes, such as those observed in the horse from the study.

Pyrrolizidine Alkaloid Toxicosis

• The research diagnosed the horse’s condition as pyrrolizidine alkaloid toxicosis. This occurs when an animal consumes plants containing pyrrolizidine alkaloids, a group of naturally occurring toxins that can cause severe damage to the liver and other organs in animals.
• Tansy ragwort is one such plant that contains a high concentration of these toxins, and was the cause of the horse’s poisoning due to over-consumption during the period of drought when other food sources were scarce.

Recovery

• The horse was able to make a full recovery once it was removed from the contaminated pasture. This case underscores the importance of monitoring the type of plants present in a horse’s grazing area, especially during periods of food scarcity such as a drought, to prevent potential poisoning.