Friday, July 18, 2008

Rare Disease Column: Tetanus

Ever gone to the ER for a few stitches in a minor wound and had the nurse ask you when your last tetanus booster was? Oh great. A shot.

Well, don't be too hard on her. Tetanus might seem like no big deal now in the age of the vaccine, but it is still a deadly menace. The number of cases reported in the US has fallen considerably since the invention of tetanus toxoid, which primes the body to immunity against the bacteria that causes this highly infectious (but not contagious) disease - Clostridium tetani (see photo).

Tetanus, known as Lockjaw prior to the 1920's, was described as early as Biblical times, and no wonder. The C. tetani bacteria can live for years in soil or animal carriers and is widespread. While it seems to prefer geographical areas that are warm, moist, and which have high levels of organic matter, it can live just about anywhere and in the inactive spore form can survive most chemical antiseptics as well as autoclaving (heating to sterilize) to 112C or 249.8F for 10-15 minutes. CDC

The real danger of C. tetani is in the toxin it produces - an exotoxin which is one of the most powerful neurotoxins known to man. Less than 200 nanograms of C. tetani's deadly neurotoxin is enough to kill most humans. The generalized form of this disease is among the most dramatic and cruel non-contagious diseases out there. The toxin produces progressive spasming of the muscles, starting with the jaw, which locks tight and prevents opening the mouth or swallowing. Sometimes the illness ends here, with the person having difficulty breathing and a quick death, but most often, the stiffening, uncontrollable muscle spasms progress down the body - the neck stiffens and hyperextends over the back, the arms and shoulders begin to posture and so forth. The spasms themselves can be so powerful as to snap bones, and for those who survive, paralysis from broken spinal cords may be a reality. ~30% of cases will not survive, however, and many will end up looking like this poor soldier (see portrait) who died shortly after this posture was seen.


So how does one get tetanus? A common misconception about the disease is that you have to step on a rusty nail, but in truth, any deep puncture, cut, or chronic wound can become infected, regardless of what caused it. Nails and tools that are left out in soil have an obvious advantage in this regard, as the soil is one of the main places C. tetani is located. However, consider the fiction implications of cultures who thrust their great swords into the dirt prior to battle (please don't try this with your katana or rapier, as your character is more likely to suffer death by virtue of having a broken weapon in battle than to inflict it upon the enemy via tetanus).

In modern times, treatment consists of managing the original wound - keeping it clean and bandaged, plus updating tetanus boosters if appropriate. In individuals who've never had a 3-dose series (which is a standard for children in the US), passive immunity can be confered by giving an injection of antibodies from another human host who is immune. Once symptoms start, the anti-toxin is of limited use, but is often still given to keep symptoms from worsening. Supportive therapy for airway, draining the bladder, providing nutrition, etc are the mainstays of treatment. Each year in the present-day US, approximately 20-100 people still develop tetanus infections, with about 10% dying, most often related to not updating boosters every 10 years or IV drug use (particularly heroin, which is sometimes contaminated with C. tetani).

Another nasty little note about tetanus - surviving it once doesn't protect someone from getting it again. Also, infants can develop tetanus from infection of umbilical cords, particularly if they are cut with non-sterile instruments, but only in mothers who are not vaccinated. The incidence of this worldwide is still relatively high, but in the US, only 2 cases have been reported in the last couple of decades.

For more information on tetanus:

Centers for Disease Control
MedLine Plus, National Institute for Infectious Disease

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