Tetanus is a dangerous nerve ailment caused by the toxin of a common bacterium, Clostridium tetani. Bacterial spores are found in soil -- most frequently in cultivated soil, least frequently in virgin soil. They also exist in environments as diverse as animal excrement, house dust, operating rooms, contaminated heroin, and the human colon. If the spores enter a wound that penetrates the skin and extends deeper than oxygen can reach, they germinate and produce a toxin that enters the bloodstream.
This toxin, tetanospasmin, ranks with botulism toxin as the most potent known microbial poison. It is taken up from the blood by the outermost nerves and moves inward toward the spine at a rate of about 10 inches a day. After 7 to 21 days, it begins to short-circuit nerve signals and block the relaxation of muscles. This results in sustained muscle contractions, notably the lockjaw for which tetanus is nicknamed.
Spasms of the jaw or facial muscles may follow, spreading to the hands, arms, legs, and back and blocking the ability to breathe. Spasms are often precipitated by noise or touch. Once tetanus has spread, the mortality rate is approximately 40%, even in modern medical facilities.
An estimated 1 million infants die of tetanus in developing countries each year because of poor hygiene. Since childhood immunization laws were passed in the United States in the 1970s, only about 50 cases a year are reported in this country; about three-quarters are elderly people or people who have never been immunized
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