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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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