The toxin enters the human body in one of three ways: by colonization of the digestive tract by the bacterium in children (infant botulism) or adults (adult intestinal toxemia), byingestion of toxin from foods (foodborne botulism) or by contamination of a wound by the bacterium (wound botulism). Person to person transmission of botulism does not occur.
All forms lead to paralysisthat typically starts with the muscles of the face and then spreads towards the limbs. In severe forms, it leads to paralysis of the breathing muscles and causes respiratory failure. In light ofthis life-threatening complication, all suspected cases of botulism are treated as medical emergencies, and public health officials are usually involved to prevent further cases from the same source.Botulism can be prevented by killing the spores by pressure cooking or autoclaving at 121 °C (250 °F) for 3 minutes or providing conditions that prevent the spores from growing. The toxin itself isdestroyed by normal cooking processes - that is, boiling for a few minutes.
The muscle weakness of botulism characteristically starts in the muscles supplied by the cranial nerves. A group of twelvenerves controls eye movements, the facial muscles and the muscles controlling chewing and swallowing. Double vision, drooping of both eyelids, loss of facial expression and swallowing problems maytherefore occur, as well as difficulty with talking. The weakness then spreads to the arms (starting in the shoulders and proceeding to the forearms) and legs (again from the thighs down to the feet).Severe botulism leads to reduced movement of the muscles of respiration, and hence problems with gas exchange. This may be experienced as dyspnea (difficulty breathing), but when severe can lead torespiratory failure, due to the buildup of unexhaled carbon dioxide and its resultant depressant effect on the brain. This may lead to coma and eventually death if untreated.
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