A Sad Story, or Why Oleander and Giraffes Don't Mix

My partner recently forwarded me a news story from Tucson, Arizona, regarding the unfortunate death of a giraffe at the Reid Park Zoo.

Based on the article, it would appear that a giraffe was accidentally fed brush trimmings that included leaves from the ornamental plant Oleander (Nerium Oleander). Oleander is a rather common ornamental plant, and is indeed ubiquitous in and around Sydney. Indeed, my primary school in South-West Sydney has a large oleander tree in the rear playground.  The leaves bear a superficial resemblance to those of the olive plant (hence the name), and have rather pretty white/pink flowers. It is rather hardy as well, being drought tolerant and capable of withstanding mild frosts, and hence has found its niche as an ornamental plant.

Pretty. Also deadly. Pretty deadly, I suppose?

Sadly, oleander is also incredibly toxic, with the leaves, bark and sap all containing a class of compounds known as cadiac glycosides. For the giraffe in the above article, what can only be presumed as an innocent mistake by a zookeeper was ultimately fatal. The response of zoo officials, in "carefully considering removing all the Oleander that's surrounding the outside of the park" is understandable.

As mentioned, oleander contains cardiac glycosides, which include the chemical oleandrin (structure below):

Definitely not giraffe friendly...

Despite the above case, cardiac glycosides are useful chemicals, and in a medical setting are used to treat congestive heart failure and arrhythmia. This use is mediated by inhibition of the sodium-potassium ion pumps present in cell membranes, which ultimately leads to an increased intracellular concentration of calcium. This, in turn, improves the force of contraction by cardiac muscle, improving cardiac output.

Unfortunately, compounds like oleandrin can also be insidiously toxic, with high doses capable of decreasing cardiac function and reducing the availability of oxygen to the tissues of the body. Without treatment, this can most certainly be fatal. Multiple cases of deaths due to ingestion (accidental or otherwise) ingestion of oleander and preparations of its leaves.  In 2000, two toddlers, aged two and three years old, died as a result of ingesting the leaves. This case is in itself unusual, as the leaves are reported to have an incredibly bitter taste, with Dr. Clarke, a medical toxicologist and director of the California Poison Control Centre, commenting that "There is not a single other case in the American literature that I know of of people eating oleander leaves and dying...".

Similarly, in the Annals of Emergency Medicine, it is reported that in 1985, a woman died after drinking a herbal tea prepared from the leaves of Neruim oleander. The article itself is interesting, as it is alleged that the woman mistook the leaves of the oleander plant for those of eucalyptus. This mistake proved fatal, as within ten hours the woman was displaying symptoms of confusion and impaired cardiac function. Staff at the hospital identified the leaves as those of the oleander plant, and took appropriate measures to prevent death. However:

"...despite these measures... the patient's cardiac rhythm deteriorated to an agonal rhythm and then to asystole. A transthoracic pacemaker was inserted... but no ventricular capture or palpable pulse resulted, and the patient was pronounced dead"

Treatment options are available in cases of oleander poisoning. Often, anti-digoxin Fab is given, which is the anti-digoxin antibody fragment. This antibody is routinely given for digoxin poisoning, which is another cardiac glycoside found in Digitalis.

Deaths due to oleander poisoning are not only limited to humans and giraffes. From livestock, including cattle and horses, through to domestic animals including dogs, oleander represents a real danger. Even goats, reputed by an old wive's tale to eat almost anything, are not immune. In general, it would appear that people are not aware of the toxicity of plants, oleander or otherwise.

As a sidenote, I feel that it would be remiss of me not to note one very interesting area of research concerning oleandrin. In the past few years, there has been some promising research indicating the possibility that oleandrin may be an anti-cancer agent. It has been found that oleandrin mediates apoptosis in tumour cells, but not in primary cells. If true, this would indicate that oleandrin may work as an anti-cancer agent with minimal side effects at the required dose. In vitro studies have also demonstrated that oleandrin may aid in the treatment of a wide range of cancers, including leukemia, pancreatic cancer and prostate cancer.

That being said, this research is still only in its early stages. However, I will be cautiously waiting for further developments in this area. This should not be an excuse for anyone to attempt ingestion of oleander. I trust that such a disclaimer is not warranted, but just to be safe, I shall include it again:

Please don't eat/ingest oleander. It really isn't a good idea. I promise. 

Until next time,
Nathan