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The following is excerpted from Dr. Jeffery Hill’s “Workshop Wound Care.” The book delves right to the heart of what you need to know when faced with common workshop injuries, from lacerations, to puncture wounds to material in the eye. Dr. Hill is an emergency room physician and an active woodworker. So he knows exactly the information a woodworker needs to know when it comes to injuries. And he presents information in a way that a non-medical professional can easily understand it.
There are a number of diseases that, due to their being very uncommonly encountered in the modern world, seem like quaint relics of antiquity. Diphtheria? Rubella? Mumps? Rabies? What even are those? There are a few diseases that have been completely eradicated (smallpox) or nearly completely eradicated (polio) thanks to sustained vaccination efforts. Tetanus, however, is here to stay on this earth through all of eternity regardless of our efforts at vaccination.
Why? Spores, that’s why
What is Tetanus?
Tetanus is a clinical condition caused by the tetanus toxin which produced by the bacteria Clostridium tetani. Clostridium tetani possesses the relatively uncommon ability to form spores (examples of other spore-forming bacteria include Clostridium botulinum, a.k.a. botulism, and Bacillus anthracis, a.k.a. anthrax).
Spores are exceptionally hardy bits of microbiology. Composed of a hard shell and just enough reproductive matter, they are typically produced when the bacteria run into rough times. A lack of nutrients, which would typically just kill off less fastidious bacteria, triggers C. tetani to produce these spores that can survive a lack of water, nutrients, presence of high amounts of radiation, freezing weather, boiling temps and even chemical disinfectants. Spores can remain viable in inhospitable environments for tens of thousands of years. C. tetani spores are most commonly found in soil, dust and manure, but can be found anywhere in the environment.
When tetanus spores find their way back to a hospitable environment they come alive and start to replicate, along the way producing tetanus toxin (awesomely named tetanospasmin). The tetanus toxin is taken up by the nervous system, ultimately ending up in the spinal cord and brain where it acts to block inhibitory signaling pathways. Because two negatives make a positive, the end result of this action is an excess of electrical transmission from the central nervous system to the muscles and severe muscle spasms.
These unopposed muscle contractions lead to the characteristic clinical manifestations of tetanus. “Lock jaw” is due to contraction of the jaw muscles. Contraction of the facial muscles results in “risus sardonicus,” a fixed smile/facial expression. And contraction of the back muscles results in severe arching of the back. But the neurotoxin doesn’t limit itself to the motor system; it can also lead to seizures and uncontrolledblood pressure (both high and low) and heart rate (also high and low).
If you have ever had a charley horse where your legs cramp up, you have a little taste of how terrifically painful muscle spasms can be. Now imagine that affecting your entire body. Also, because the tetanus toxin irreversibly binds with nerve cells, the uncontrolled nerve signals and muscle spasms continue until the body can grow new nerve endings (a process that is weeks to months long). Generalized tetanus can lead to broken bones, spasm of the respiratory muscles, and aspiration of stomach contents and food into the lungs. Ten to 20 percent of patients still die of tetanus despite modern medical therapies.
What Wounds are at High Risk for Tetanus Infection?
Tetanus infections don’t just come from rusty nails. In fact, all wounds – cuts, abrasions (both to the skin and eyes) and burns – are susceptible to tetanus infection. There are certain wounds, however, that are more prone to tetanus infection and create an environment where the tetanus bacteria will produce the tetanus toxin. Wounds that are dirty, puncture-type wounds and crush injuries are most at risk.
Logically, the more tetanus bacteria present in a wound, the higher the risk of infection. As such, injuries with significant contamination with soil are more likely to result in infection.
If the tetanus bacteria is pushed deep into the tissue, infection is more likely. Puncture wounds, in general, carry a higher risk of all types of wound infection. The narrow tract of a puncture wound is apt to quickly close over bacteria and other matter pushed deeply into the tissues. And, it is much more difficult to adequately clean at the time of injury, meaning it is much more difficult to use irrigation to decrease the number of bacteria present.
Because tetanus bacteria are more likely to grow and produce toxin in “devitalized” tissue, crush injuries are also highly susceptible to infection.
How does this translate to you, the woodworker? A scratch or minor cut from a chisel or knife is less risky. A injury from an axe or froe while breaking down green wood is more risky. (Though to reiterate: Any break in the skin carries a risk of tetanus infection.)
What About the Tetanus Vaccine?
The tetanus vaccine includes a component of the tetanus toxin called a toxoid. This toxoid is coupled with a diphtheria toxoid (Td) and often an acellular version of pertussis (TdaP).
As a side note, the risks of contracting diphtheria and pertussis in adulthood are sufficient enough that the administration of the whole package of TdaP is recommended by the CDC. Pertussis (whooping cough) can be common in older adults (often presenting as mild illness) and easily spread to incompletely vaccinated infants (often presenting as a severe respiratory illness). For this reason, if you are going to be around a new baby in the family (e.g. new grandparents), you’ll likely be asked to get a “tetanus booster” (though really you are boosting your pertussis immunity). Back to tetanus…
As with other vaccines, introducing the tetanus toxoid gives the body’s immune system a “wanted” poster of what the real toxin looks like, allowing the body to create neutralizing antibodies to the toxin. The typical vaccination schedule is for three doses of the vaccine to be administered at two months, four months, and six months of age, with boosters given around six to 12 months after the third dose, and again before entering kindergarten. Following that, boosters are recommended every 10 years. In the developed world, adherence to the recommended vaccination schedule is (thankfully) high, meaning that most people are “fully vaccinated” for tetanus through their childhood. It is not uncommon, however, for adults to miss out on their regular boosters. As a result of this, most cases of tetanus are reported in patients 50 years of age and older.
