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Biotoxins

Common Characteristics

• Are by-products of bacteria or naturally occurring chemicals
• Do not replicate within the host
• Are not communicable
• LD₅₀ is quite low
• Can produce significant life-threatening disease when delivered as an aerosol

Clostridium botulinum Neurotoxin

• Three naturally occurring forms are recognized: food-borne, wound, and infant
• Inhalation botulism could occur if toxin is intentionally delivered as an aerosol
• The neurotoxin binds presynaptically to the cholinergic nerves blocking the release of acetylcholine producing severe neuromuscular paralysis
• Early symptoms include ocular paresis, rotatory nystagmus, dilated pupils, dysarthria, ataxia, and generalized weakness
• Clinical pearl: A young person presenting with difficulty swallowing and speaking who has not suffered a cerebral vascular accident is most likely to have botulism
• Electromyography may help to establish the diagnosis and a rabbit bioassay is available for confirmation
• The antitoxin is active against serotypes A, B, and E
• Treatment must be initiated when disease is suspected, without waiting for laboratory confirmation
• Trivalent antitoxin will prevent progression but will not reverse paralysis once it occurs
• Antibiotics are not indicated for inhalational botulism

Ricin

• A toxin that is derived from the castor bean, Ricinis communis
• Following inhalation, symptoms occur after 8 hours producing a necrotizing pnuemonitis and pulmonary edema
• After parenteral administration:
• • Local pain
  • Fifteen to 24 hours later, nausea, vomiting, fever, and localized lymphadenopathy proximal to the injection
  • After 48 hours, a sepsis-like syndrome occurs with hypotension, leukocytosis, DIC, multi-organ system
• Diagnosis may be confirmed by an ELISA assay
• Treatment is supportive:
• • A formalin-treated toxoid has had preclinical testing and may be available through the CDC as an Investigational New Drug

Staphylococcal Enterotoxin B (SEB)

• A superantigen that stimulates the major histocompatibility complex, producing a multi-system disease resembling sepsis:
• • Examples include toxic shock syndrome and staphylococcal food poisoning
• SEB is considered an incapacitating agent, although it can be lethal to some exposed victims
• After aerosolized exposure, respiratory symptoms predominate:
• • Within 10 hours, non-productive cough, dyspnea, orthopnea occur
  • Headache, chest pain, myalgias, nausea, and vomiting can also occur
  • An elevated white blood cell count, hypoxia, and a chest x-ray consistent with pulmonary edema may be seen
  • Most symptoms resolve within 24 to 36 hours, but exertional dyspnea may persist for 10 days
• The SEB toxin may be detected on nasal swabs early in the course of the illness
• For rapid detection, a PCR amplification is available from the CDC
• Treatment is supportive:
• • Since sepsis and pneumonia are in the differential diagnosis, antibiotics should be administered pending confirmatory tests

Trichothecene Mycotoxin (T-2)

• A mycotoxin that inhibits DNA and protein synthesis and, to a lesser extent, RNA synthesis
• Trichothecene occurs naturally in nature and can be manufactured in large quantities
• The toxin is rapidly taken up across the pulmonary and gastrointestinal mucosa and more slowly through the skin
• Skin exposure causes burning, blistering, petechiae, and ecchymoses
• Ocular exposure can cause burning and corneal opacification
• Respiratory exposure causes cough, pleuritic chest pain, dyspnea, and hemoptysis
• Gastrointestinal symptoms include hematemesis, abdominal pain, and bloody diarrhea
• Diagnosis can be suspected when exposure to a yellow oily liquid occurs, followed by the constellation of symptoms described
• Environmental or biological samples can be used for confirmation using gas chromatography-mass spectrometry
• Emergency measures include immediate skin decontamination with soap and water and isolation of contaminated clothes
• Treatment is supportive

B. Zane Horowitz, MD, FMACT
Oregon Poison Center
Oregon Health Sciences University

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