|Scientific Name(s)||From the castor bean plant Ricinus communis|
|Physical Attributes||From the seed of the castor plant, inhibits protein synthesis|
|Mode(s) of Transmission||Breathing in ricin mist or powder, swallowed (powder or dissolved in liquid), injection; not contagious|
|Likely BW Form(s)||Aerosol; it can be dissolved in liquids; injected|
|Vector/Dormant Form||Powder, a mist, or a pellet; stable substance|
|Fatality||Lethal dose: of 3 - 5 mcg/kg are lethal inhalation; 20 - 40 mcg/kg ingestion|
|Vaccine||Experimental (as of 2007): RiVax contains a recombinant subunit of the A chain of ricin toxin|
|Treatment||No antidotes; supportive care|
Ricin is a glycoprotein toxin (66,000 daltons) from the seed of the castor plant. It blocks protein synthesis by altering the rRNA, thus killing the cell. Ricin can be in the form of a powder, a mist, or a pellet. It can be dissolved in water or weak acid. It is not contagious. Ricin's significance as a potential biological warfare agent relates to its availability world wide, its ease of production, and extreme pulmonary toxicity when inhaled in aerosolized form.
Depending on the route of exposure (such as injection or inhalation), as little as 500 micrograms of ricin could be enough to kill an adult. A 500-microgram dose of ricin would be about the size of the head of a pin. A greater amount would likely be needed to kill people if the ricin were swallowed.
Death typically occurs 36-72 hours after exposure; if no death occurs 3-5 days after exposure, the victim survives. Ricin poisoning differs from anthrax in that the activation of anthrax spores takes at least 24 hours and sometimes several days while ricin symptoms typically manifests itself 4-12 hours after exposure. The clinical picture depends on the route of exposure. All exposures typically develop fever, coughing and gastrointestinal complications.
Following inhalation, within a few hours of inhaling significant amounts of ricin, the likely symptoms would be respiratory distress (difficulty breathing), fever, cough, nausea, and tightness in the chest. Heavy sweating may follow as well as fluid building up in the lungs (pulmonary edema). This would make breathing even more difficult, and the skin might turn blue. Excess fluid in the lungs would be diagnosed by x-ray or by listening to the chest with a stethoscope. Development of flesh eroding lesions long the airways contribute in respiratory and heart failure. Finally, low blood pressure and respiratory failure may occur, leading to death. In cases of known exposure to ricin, people having respiratory symptoms that started within 12 hours of inhaling ricin should seek medical care.
The symptoms of ricin poisoning resemble those induced by sarin gas or gas phosgene used in World War I. However, while sarin gas kills instantly, death due to ricin poisoning takes several days.
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. Dehydration, hallucination, seizures and blood in the urine may result. Death typically occurs on the third day or later after possible liver, spleen or kidney failure. Ricin poisoning can also occur when injected into humans or from physical contact.
Physical contact with ricin in powder or mist form can cause redness and pain of the skin and the eyes.
Therapy for ricin poisoning is supportive. Care could include such measures as helping victims breathe, giving them intravenous fluids (fluids given through a needle inserted into a vein), giving them medications to treat conditions such as seizure and low blood pressure, flushing their stomachs with activated charcoal (if the ricin has been very recently ingested), or washing out their eyes with water if their eyes are irritated. There is presently no antitoxin available for treatment.
As for 2007, there is no prophylaxis approved for human use. Active immunization and passive antibody prophylaxis are under study, as both are effective in protecting animals from death following exposure by intravenous or respiratory routes. In case of exposure to aerosolized ricin poisons, the Center for Disease Control (CDC) suggests that one should get to fresh air, remove clothing, and wash the poison from skin with water and soap as soon as possible.
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