Toxic Castor Beans

May/June 2003 California Veterinarian

Toxic Castor Beans: A Weapon of Terrorists Right in Your Own Backyard

By Susan Norlund MA, BS, RVT, RLATG

Knowledge of toxic plants in your area can save a life. RVTs can frequently intervene early enough, or sometimes even prior to a tragedy, to minimize lethal effects of toxic plant ingestion. One of the best tools in our arsenal is knowledge and the ability to recognize a description of these dangerous plants.

Commonly occurring locally grown plants, fruits, or seeds can result in a painful death if ingested by an unknowing horse or a playful puppy or dog. We can learn to identify these plants and be on alert if an owner calls with a description of the painful symptoms that can be caused by ingestion of a poisonous botanical.

Many of us are familiar with oleander and other frequently seen botanical threats, but do you know about the lethal effects of the common castor bean? One of the most toxic and deadly natural toxins known to man grows wild in much of California as a common weed. You’ve probably seen this deadly plant countless times without taking notice. It is a familiar sight along roads and highways and scattered across countryside and pastures.

My first exposure to this botanical was while working as a technician at the Emergency Pet Clinic of Pomona Valley in Montclair. Dr. Marcy Locke, an experienced emergency veterinarian, was on duty. A very distressed owner brought her diminutive and much-loved dog into the hospital for evaluation. The dog was in great pain and was experiencing gastrointestinal bleeding, as well as other symptoms.

Under Dr. Locke’s careful and thorough questioning, the owner revealed the little dog had eaten some beans from an unknown plant growing in her backyard. The owner was shown a picture of the castor bean plant. Fairly certain that this was, in fact, the very type of plant growing in her backyard, the owner went home and gathered some of the beans and brought them to the hospital. Sadly, the small dog had eaten one of the most lethal substances in the plant world.

The castor bean plant (Ricinus communis) produces a toxin called ricin, reported to be a tool of terrorists and a weapon of murderers. Ricin is a powerful cytotoxin. The substance is so deadly that it is estimated that just one milligram can prove fatal to an adult human. Cornell University reports that ricin was used to assassinate a Bulgarian journalist who had criticized the government. The unfortunate victim was said to have been stabbed with an umbrella point. A perforated metallic pellet containing ricin was found imbedded in his leg. More recently, British police raided two addresses in London and found traces of ricin, presumably to be used in terrorist

The castor bean plant is in the family of Euphorbiaceae, or Spurge family. It is also known as Palma Christi, African coffee tree, mole bean (it has been used to deter moles in gardens), wonder tree, drapata, and djarak. Castor bean plants, introduced to this country from the West Indies, are native to tropical regions of Africa. They have large palmated leaves with six to 10 lobes. The plants grow as a perennial in the warmer zones of California and can reach heights of 15 to 30 feet. The palmated leaf of the plant is sometimes described as having the appearance of a giant marijuana leaf. The stem attaches to the center of the leaf, which can grow from four to 30 inches across. The foliage is generally green, but some varieties have a brownish red cast, with slightly serrated leaf edges. Each leaf has a central vein that is easily visible.

The plant produces reddish brown or greenish flowers, which grow on an upright stalk. The seeds are contained in soft, spiny pods that are also green or reddish brown. The large, deadly seeds (one to a pod) are usually medium brown or tan in color with mottled dark spots. They can look like large, fat ticks and are 10 millimeters long and six to seven millimeters wide. They have a flattened, oval shape.

Ricin is a phytotoxin and a water-soluble protein. The highest concentration of the toxin is in the seed, although the entire plant is toxic. This deadly bean sometimes grows in and around pasture lands and can prove deadly to livestock grazing in the area or to animals that consume plant parts that may have inadvertently been incorporated into feeds. For that reason, horses are especially susceptible. Twenty-five grams of castor bean seed is described as a lethal dose for a horse.

Animals that ingest castor beans are stricken with symptoms that frequently include abdominal pain, bloody diarrhea, hemorrhagic gastroenteritis, and tachycardia. Symptoms occur within hours of ingestion and can result in death within days. If the seed coat is not broken by mastication, survival is reported to be likely.

The castor bean is frequently used in crafts and is also strung into beaded necklaces. These beans should be kept securely away from pets as well as children.

On another note, castor beans are commercially pressed to extract castor oil, which is used for medicinal purposes and has a worldwide market of more than $400 million annually. Castor oil does not contain ricin, which is water-soluble and so does not partition into the oil. Because of their toxicity, however, castor bean plants are not grown extensively in the United States. Instead, more than $41 million worth of castor oil is imported every year. The U.S. Department of Agriculture is working on a genetically engineered castor bean plant that might be less deadly than naturally occurring varieties.

Susan Norlund is a Registered Veterinary Technician and an AALAS Registered Laboratory Animal Technologist. She worked for several years in emergency medicine before moving to care of canines with cardiac problems and pacemaker research. She recently began working in diabetes research with canines.

© 2019 California Veterinary Medical Association

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