"Toxin" is often loosely used to refer to any poison but technically refers only to a poisonous chemical produced by an organism (although some toxins can now also be produced synthetically). Because toxins used as mass casualty weapons do not include the infectious agents from which they are derived, they are not transmissible from person to person. Thus, toxins are more like chemical agents than biological agents because they cause poisoning rather than infection.
Hundreds of toxins are known. However, it is difficult to make large quantities of most toxins and hard to distribute toxins widely enough to affect many people. Thus, most toxins are more suited to assassination than to creating mass casualties. Only four toxins are considered high-threat agents by the US Centers for Disease Control and Prevention (CDC):
Of these, only botulinum toxin is classified among the highest priority agents. Epsilon toxin from C. perfringens is mainly of historical interest as an agent reportedly developed by Iraq in the 1980s.
Botulinum toxin, or botulinum neurotoxin, refers to any of seven known types of neurotoxins produced by the bacterium Clostridium botulinum. Food-borne, wound, and infant botulism are described elsewhere (see Botulism). Mass casualties from botulinum neurotoxin could occur from widespread contamination of food or water, but the most likely scenario would be inhalation of an aerosol form.
Botulinum neurotoxin blocks one of the types of chemicals that nerve cells use to send signals to other nerve cells and to muscles (neurotransmitters). Because the particular signaling chemical, acetylcholine, does not work properly, people become weak or paralyzed. Typically the paralysis starts at the top of the body about 12 to 36 hours (range 2 h to 8 days) after exposure to botulinum neurotoxin and extends downward. The toxin does not enter the brain, so thinking is not affected.
Doctors give an antitoxin by vein. The antitoxin becomes progressively less effective as symptoms and signs develop.
Ricin and Abrin
Ricin comes from beans of the castor plant, and abrin comes from jequirity, or rosary pea. Although ricin has been injected in assassination attempts, mass casualties would probably involve inhalation of an aerosol form of the toxin.
Symptoms of ricin and abrin poisoning vary by route of exposure. Within 4 to 8 hours of inhalation exposure, people develop cough, respiratory distress, and fever. Many organs are progressively affected over the next 12 to 24 hours, culminating in respiratory failure and often death. No specific antidote or antitoxin is available, and treatment focuses on supporting the person's breathing.
Staphylococcal Enterotoxin B
Staphylococcal enterotoxin B is one of 7 enterotoxins (toxins acting in the intestine) produced by the bacteria called Staphylococcus aureus. Staphylococcal enterotoxin B is responsible for staphylococcal food poisoning when ingested (see Staphylococcal Food Poisoning). Mass casualties could result from deliberate contamination of food but also from inhalation of an aerosol form of the toxin.
Symptoms typically occur 1 to 12 hours after ingestion and 2 to 12 hours (with a range of 1.5 to 24 hours) after inhalation. After initial flu-like symptoms of fever, chills, headache, and muscle aches, subsequent symptoms depend on the route of exposure. Ingestion causes nausea, vomiting, and diarrhea for 1 to 2 days. Inhalation causes cough, chest pain, and often nasal irritation and congestion. Eye inflammation (conjunctivitis) can result from contact of the aerosol with the eyes. Inhalation can rarely cause death. In survivors, fever may persist up to 5 days and cough for 4 weeks. Special laboratory tests may help doctors confirm the diagnosis. Doctors aim treatment efforts at relieving the person's symptoms.
The views expressed in this article are those of the author and do not reflect the official policy of the Department of Army, Department of Defense, or the US Government.
Last full review/revision January 2014 by James Madsen, MD, MPH