Aug 30, 20195 min read

Some dangerous biotoxins

Updated: Jan 24, 2020

the yellow and black bio-hazard symbol used globally — The bio-hazard symbol

Toxin, venom, and poison—although these might sound similar, they are not the same thing. Venom is a toxin, so too is poison. But what sets these two entities apart is their mode of entry into the body. While the venom is injected into organisms, poison can enter the body through dermal absorption, inhalation, ingestion, etc. When talking about venom, think of animals like snakes, spiders, and scorpions; organisms that bites and stings, and while speaking of poison, think of mushrooms and plants—things that need to be consumed, or touched to cause harm.

Diethyl mercury and lead are harmful to living cells as well, but these synthesized chemicals are generally referred to as toxicants. While these are considered toxic, the term ‘toxin’ is normally reserved for certain substances produced naturally by plants, microbes, and fungi. This list is about six such biological toxins or biotoxins hidden in plain sight.

Ricin

First off is a plant-based poison found in castor seeds called Ricin. The rich availability of castor oil plants across the globe makes this poison all the more scarier. The whitish-yellow toxin, however, pertains only to castor beans and the waste product from the castor oil extraction process. The castor oil is considered perfectly safe to organisms in normal concentrations.

A median lethal dose or LD50[1] is used as the measure to determine the acute toxicity of a substance, and it is defined as the dose required to kill half of a test population, generally mice or rats, under specific test conditions. The lower the LD50, the more potent the toxin, and depending on the mode of entry of a toxin into the body, the LD50 value varies. An LD50 value of 3 µg/kg[2] bodyweight for humans, makes ricin most dangerous[3] when inhaled.

Tetrodotoxin

Tetrodotoxin is famous for its origin. The toxin is harbored by a bunch of marine species, the most well-known being the pufferfish, locally called the fugu, a delicacy in Japan.

Puffer fish, otherwise known as fugu is consumed as a delicacy in Japan — Puffer fish/ Photo by Brian Yurasits @ Unsplash/ see link under sources

Care should be taken while preparing the dish since this toxin vests in various parts of the fish, including its skin, and therefore the chefs require a special license to prepare fugu. Tetrodotoxin is a neurotoxin[4] which inhibits neural transmission, leading to body paralysis and in severe cases, cause death in a very short period. A case in a journal article[5] reports a Japanese woman who showed symptoms of partial limbic paralysis after the consumption of fugu. However, she recovered after 24 hours and showed no signs of poisoning a week after. The toxin has no known antidote.

Abrin

Abrin is another plant-based toxin found in the rosary pea plants. The toxin lies within the seeds of the plants and could be deadly even in small amounts. The estimated median lethal dose for humans is as small as 0.1-1 µg/kg[6] bodyweight, which makes it the most potent plant toxin in the world. Depending on the mode of entry into the body, the symptoms can range from vomiting and diarrhea to neurological effects like hallucinations. Like Ricin, Abrin is more toxic when inhaled.

Saxitoxin

Mussels arranged on a plate, ready to be served; also a source of shellfish poisoning — Photo by Nick Karvounis @ Unsplash/ Link under sources

Much like tetrodotoxin, saxitoxin is also found predominantly in marine environments and is known to cause the notorious shellfish poisoning. The shellfish, however, does not produce the toxin but is rather produced by algae. The toxin-producing microbes get preyed on by mollusks like shellfish during algal blooms, and the toxin accumulates within their tissues. The intoxication effects range from dizziness and headache in mild cases[7], to paralysis and breathing arrest in very severe cases, which may even lead to death in a few hours.

Batrachotoxin

Batrachotoxin is perhaps the odd one out in the list, for it is difficult to come across in everyday life. This toxin is found in beetles, and certain bird species, but its most documented source is the poisonous frogs of South and Central America. About 136µg of batrachotoxin[8], equivalent to two grains of table salt, is enough to kill a human weighing 68 kg, and a poison frog can pack as much as eight times more batrachotoxin in its skin! It affects the nervous system, and severe intoxications may lead to cardiac arrest.

The poison dart frog found in the amazon contain lethal doses of poison in its skin — Poison dart frog/ Zachary Spears @ Unsplash/ see link under sources

Botulinum neurotoxin

Saved the best for the last. Botulinum neurotoxin is indeed your average toxin in terms of availability, yet the deadliest when it comes to potency. So, how is it that it’s available in the market as a therapeutic agent? Well, the devil lies in the details. When used for medical purposes, the botulinum is mixed with other substances and is known as Botox[9], and it only consists of a tiny amount of the real stuff. Even though the Botox injections are administered professionally, side effects are still reported. However, this toxin is also known to enter the body through an entirely different means. Improperly canned foods harbor suitable anaerobic conditions for the toxin-producing Clostridium botulinum bacteria, which can lead to a condition known as botulism if consumed.

It only takes the tiny amount of 0.7-0.9 µg of botulinum toxin to kill a 70 kg human[10]. It’s even estimated that a cup full of pure botulinum toxin is capable of wiping out the entire population on earth[11]. Due to its high potency, easy availability, and difficulty in detection, centers for disease control and prevention[12] consider it as a category A bioterrorism agent.