Botulism.
Botulinum toxin is the most potent toxin known to humans and as little as 100 ng can be lethal. The toxin blocks peripheral cholinergic neurotransmission at the neuromuscular junction and cholinergic autonomic nervous system by introducing an endopeptadase enzyme into the presynaptic side of the synapse. The endopeptadase cleaves acetylcholine vesicle docking proteins that are required for the synapse to release acetylcholine into the synaptic cleft. Botulism occurs from consumption or inhalation of preformed botulinum toxin or growth of Clostridium botulinum bacteria in the infant gastrointestinal tract or within a wound. Growth of C. botulinum in the immature gut or wound will release botulinum toxin that reaches the circulation. All forms of botulism cause progressive weakness, bulbar signs (blurred vision, diplopia, mydriasis, dysphagia, and dysarthria), and respiratory failure with normal sensation and mentation. Treatment is aimed at 1) maintaining respiration via intubation and mechanical ventilation, 2) stopping progression of weakness by administration of botulinum antitoxin (equine trivalent botulinum antitoxin for adults and botulism immune-globulin intravenous-human for infant botulism), and 3) preventing complications from weeks of paralysis with good supportive care. The source of the botulinum toxin should be identified to prevent additional cases. Patients can recover normal muscle strength within weeks to months, but usually complain of fatigue for years.