The following information contains adaptations and excerpts from the US Army Center for Health Promotion and Preventive Medicine (USACHPPM) Tech Guide 244, The Medical NBC Battlebook.

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Characteristics. Ricin is a glycoprotein toxin from the seed of the castor bean plant. Altering ribosomal RNA blocks protein synthesis, thereby killing infected cells. Ricin's significance as a potential biological warfare agent relates to its availability worldwide, ease of production, and extreme pulmonary toxicity when inhaled.

Clinical Features. Overall, the clinical picture seen depends on the route of exposure. All reported serious or fatal cases of castor bean ingestion have taken approximately the same course: rapid onset of nausea, vomiting, abdominal cramps and severe diarrhea with vascular collapse. Death usually occurs on the third day or later after exposure. Following inhalation, one might expect nonspecific symptoms of weakness, fever, cough, and hypothermia followed by hypotension and cardiovascular collapse. In monkeys, inhalation toxicity is characterized by a dose dependent preclinical period of 24-36 hours followed by anorexia and progressive decrease in physical activity. Death occurs 36-48 hours post challenge. High doses by inhalation appear to produce severe enough pulmonary damage to cause death.

Prophylaxis. There is currently no prophylaxis approved for human use. Ricin in not dermally active; therefore, respiratory protection is the most critical means of prevention (similar to chemical agent exposure). Vaccines under development are immunogenic and confer protection against lethal aerosol exposures in animals.

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