Cookies Linked to Horse Death

Cookies Linked to Horse Death

Even when ingested in small quantities oleander is toxic to horses.

Photo: iStock

One California horse is dead and another recovering after being poisoned by cookies laced with oleander.

Oleander (Nerium oleander) is a leafy, flowering, drought-resistant plant used in ornamental landscaping in several parts of the United States, including California, Utah, Arizona, and Texas. It contains cardiac glycosides that can cause various clinical signs of toxicity in horses, including colic, lack of coordination, profuse sweating, difficulty breathing, abnormal heart function, muscle tremors, and potentially death from cardiac failure. As little as one ounce can be fatal to some horses.

“Oleander causes weakness (and) depression,” said Anthony P. Knight, BVSc, MS, Dipl. ACVIM, professor in the College of Veterinary Medicine at Colorado State University. “The toxin is like digitalis; it works on the heart muscle.”

Sergeant Cecile Focha, public information officer for the Sonoma County, California, Sheriff's Office said that an owner reported that two of her horses appeared to have been poisoned on Feb. 12. One horse survived, but another subsequently died; a dog also died in connection with the incident, she said. Necropsies revealed that the horse and the dog had died due to oleander toxicity, Focha said.

Leslie Webb, owner of the horse and dog that died, said the home-made cookies contained oatmeal, shredded apple, shredded carrot, and some had been soaked in molasses. The cookies had been placed on the ground along the fence line near a roadside. Others were placed in a paddock containing the horses.

“Somebody had to climb onto the property to do this,” she said.

Webb said that she called police as soon as the found the cookies. A toxicology report revealed that the cookies tested positive for the presence of ground oleander, she said.

Focha said that the placement of the cookies was intentional and that the poisoning seems to be an isolated incident, she said.

“While there may be other recent livestock deaths, there is only this sole incident of confirmed intentional poisoning,” Focha said. “This is very rare, at least around here.”

Focha said the Sonoma County Sheriff's Office’s Rural Task Force is investigating the incident.

“We are following up strong leads that have identified a person of interest,” Focha said.

As the probe continues, anyone with information about the incident should call the Sonoma County Sheriff's Office Tip Line at 707/565- 2185 or submit information via the Silent Witness form on the office’s website. 

Further, anyone who believes that their animal was intentionally killed by oleander poisoning should call the sheriff's office at 707/567-2511.

Editor's Note: This article was updated on Feb. 26 to include additional information obtained by

About the Author

Pat Raia

Pat Raia is a veteran journalist who enjoys covering equine welfare, industry, and news. In her spare time, she enjoys riding her Tennessee Walking Horse, Sonny.

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