Toxic plants (Proceedings)


Toxic plants (Proceedings)

Nov 01, 2009

It is not uncommon for veterinarians working with companion animals to run into suspected intoxications where the actual toxicant cannot be identified. There is almost never a lack of potential perpetrators of these dastardly deeds, because of the somewhat morbid, seemingly natural inclination for people to think there is someone who hates them enough to kill their pet. However, clients are often extremely reluctant to consider or are, even possibly, unaware of the wide variety of common and, sometimes, not so common indoor and outdoor ornamental plants, which if consumed in large enough quantities, can result in potentially lethal intoxications. It has been my experience that, like me almost 30 ago, veterinary professional students still seem to think that toxic plants are the exclusive domain of large animal practitioners and that 500 plants can be memorized the night before the exam. Because livestock species are generally herbivorous or, at least, omnivorous and are generally kept as groups of animals, it might be true, to some extent, that equine and food animal veterinarians do encounter larger numbers of animals affected by plant-related toxins than their small animal colleagues. However, there are certainly plant intoxications with which small animal practitioners should be familiar, especially if their patients have access to palatable indoor and/or outdoor plants and are young, small, overly curious, bored, hungry, just plain stupid and destined to eventually be a Darwinian phenomenon, and/or any combination of the preceding factors.

We are often left to believe that if something is "natural" it is at least safe, if not beneficial. While many natural products do, in fact, have inherent benefits and, even, medicinal value, it should not be assumed that chemicals of plant origin are necessarily less potent or safer than synthesized products. Nature is NOT benign!!! Chemical warfare expertise is essential to the survival of some plants because they are immobile and relatively defenseless. The toxic principles in plants include various classes and mixtures of classes of compounds, such as Alkaloids, Proteins, Peptides, Amino Acids, Glycosides, Oxalates, Tannins, Resins, Nitrates, Sulfides and some Unknown Compounds. No mammalian organ system is immune to the effects of plant toxins, and toxic plants and/or plant toxins can affect multiple systems. It should be understood that, as greater quantities of a toxic plant are consumed, more severe clinical signs are likely to be observed. In addition, different syndromes can be seen in different species and with different levels of toxic exposure.

A systems approach will be used in three hours of lecture to cover some of the more relevant plants with which small animal practitioners should have some familiarity. The plants will be grouped as CARDIOTOXIC AND NEUROTOXIC PLANTS, NEPHROTOXIC AND HEPATOTOXIC PLANTS, and, finally, OTHER COMMON AND NOT SO COMMON TOXIC PLANTS, which primarily affect other systems. While plants will be discussed under one system, an effort will be made, when necessary, to mention other systems potentially affected by a particular plant or related species.

Cardiotoxic and neurotoxic plants

It can sometimes be difficult to tell whether an apparent intoxication involves primarily cardiac or neurological abnormalities. Nonspecific clinical signs, such as weakness, tremors, and gastrointestinal upset, can often be observed with exposure to either cardiotoxic or neurotoxic plants. Small doses of cardiotoxins and neurotoxins can also both cause rapid death, without much in the way of premonitory signs or postmortem changes. Careful examination, including auscultation of the heart and ancillary testing procedures, performed in the earliest stages of a suspected intoxication, can often detect cardiac arrhythmias or subtle neurological deficits, which distinguish the effects of cardiotoxins from those of neurotoxins.