Prior to the fall of 2001, very few individuals in the Unites States, outside of the Centers for Disease Control (CDC) or the military, gave much thought to the possibility of a biological attack on this country. The events of September 11, 2001 and the anthrax attacks through the postal service in October of 2001 changed the perceptions of most Americans. While anthrax, smallpox and other biological agents have been media buzzwords for the past seven years, many other agents remain unknown to the general public. One of these unknowns is Staphylococcal Enterotoxin B or SEB.
The History of Staphylococcal Enterotoxin B
SEB was one of the many agents studied by the United States Army for use in a biological weapons attack during the Cold War. SEB was weaponized during the 1960's and stockpiled until 1969 as Agent PG. It remained as part of the biological arsenal while the United States maintained an offensive biological capability until the Biological Weapons Conventions of 1972. Like other biological weapons, SEB was developed due to the extremely small amounts needed to incapacitate its intended victims. It is listed as a Category B agent by the CDC.
SEB may be either inhaled through the lungs or ingested through the intestinal tract. Both routes of exposure yield different results. For inhalation, the dose required to kill 50 percent of a target population (LD50) is only 0.0014 grams. The dose required to incapacitate 50 percent of a target population (ID50) is even less at 0.000028 grams (Ellison, 2008). With numbers such as these, it is easy to see why biological weapons have been identified as the "poor man's atomic bomb".
Like all toxins, SEB is normally found in nature. It is not a man-made weapon such as a nerve or blister agent. Very little information exists as to how or where SEB occurs in nature. (Ulrich, 1997) Infections have been found in rodents, sheep and cattle. It has been the cause of numerous outbreaks of food poisoning, but the exact numbers cannot be known. Many incidents of food poisoning go either unreported or are simply written off as a case of the "stomach flu". Many people do not realize they have contracted food poisoning and therefore misdiagnose themselves. This makes tracking cases of SEB outside of the laboratory environment extremely difficult.
SEB has not been confirmed as having been used in any act of bioterrorism. Just because it has not, does not mean it will not. While American stockpiles have either been destroyed or held under rather tight security, the same cannot be said about stockpiles held by the former Soviet Union. The United States has been assisting the former Soviet states, but the issue is still in doubt.
SEB is the second most common cause of food poisoning, making it quite common outside of the laboratory. Some knowledge and rudimentary laboratory equipment could produce a weaker strain of SEB. This weaker strain may not be as lethal or incapacitating as weapons grade SEB, but the results (straining local emergency medical services (EMS) and public health agencies in addition to instilling fear into the general public) will still be achieved.
The bacteria can be grown in a growth medium or agar in a Petri dish. The colonies will continue to replicate until thousands of them exist. The bacteria can then be freeze dried to form a spore. The spores remain relatively stable for years and are extremely difficult to detect for first responders in the field.
Signs & Symptoms of SEB
The primary routes for SEB to invade the body are inhalation and ingestion. Inhalation will result in a faster onset of symptoms, but they will be somewhat different than the signs and symptoms demonstrated by ingestion.