++
Biotoxins occupy a middle ground
in the spectrum between chemical and biological agents (Table 17–1). Neither
a living entity, such as bacteria, nor a laboratory invention, such
as nerve gases, biotoxins are products of metabolic pathways that
are toxic to humans. Some are made by single-celled organisms, whereas
others are derived from multicellular organisms. Naturally occurring
biotoxins may also be reproduced synthetically. Biotoxins can be
extremely potent, but they are not communicable and do not replicate
within the host. For this reason, properly decontaminated patients
pose no risk to health care workers (HCWs) and others with whom
they may come into contact. The clinical impact of biotoxins is
arguably more akin to chemical weapons than to biological weapons; however
their biological origins tie them in readily with biological weapons.
++++
Exposure to biotoxins occurs through ingestion, dermal absorbtion,
or as an aerosol. Militarily or as a weapon of terror, aerosol forms
of biotoxins pose the greatest risk not only in terms of numbers
of people exposed, but the rapidity of symptom onset. With some
of the biotoxins, inhalational effects are understood only from
animal studies, leaving many open questions about how an inhalational
exposure might present. Not all biotoxins are likely candidates
for use as weapons of mass destruction or terrorist weapons. Due
to their biological and physiochemical properties, Army biowarfare
experts consider botulinum toxin and Staphylococcal Enterotoxin
B (SEB) to be of most concern from the point of view of battlefield
exposures. SEB, a so-called superantigen, causes hyperactivation
of the immune system and prompt incapacitation (see Chapter 19).
As a Category A agent, botulinum is discussed in its own chapter
(Chapter 18).
++
Since terrorists may have more limited goals—for example,
sowing fear, as was seen with anthrax—wider options in
regard to potential biotoxin weapons, including ricin, abrin and
mycotoxins, exist. This, too, is discussed briefly.
++
The CDC classifies the biotoxins as biological weapons. Others
make biotoxins a category unto itself, or classify them as chemical
agents. For the purposes of this text, we have chosen to follow the
CDC categorization, thereby providing discussion of particular biotoxins
according to their Category A and Category B biological weapons
designation. The only exception is ricin, which although listed
with Category B agents by the CDC ...