This morning I heard a newscaster lament, “I was cut with rusty metal, and there is a national shortage of tetanus vaccine.”
Despite his concerns, this is not exactly certain death. Growing up in Southern California, I spent most of my youth barefoot, tangled with more than a few rusty nails and was on the tetanus-shot-a-year plan. This experience prompted an interest in the whole rusty nail tetanus connection.
What about rusty nails and tetanus? Tetanus is actually caused by a germ, not by rust. This germ is in spore form and lives in the dirt. The technical name is clostridia tetani. Clostridia is a bad family of bugs; its relatives cause botulism and gas gangrene. Pretty unpleasant stuff.
Rust is the oxidation product of iron. Oxidation is a form of chemical burning. You are familiar with this – this is what chlorine does to your swimming pool. It oxidizes germs, meaning it kills them. Rust is not infectious for anything, including tetanus. Yes, I said rust does not cause tetanus, and reading in the dark won’t ruin your eyes. So much for medical myths.
The concern is getting dirt in the wound, which may contain clostridia tetani spores. If these spores find a friendly environment in your wound, you can get tetanus. These spores don’t like a lot of oxygen, so wounds that have a lot of dead tissue, like road rash, are perfect for growing clostridia tetani. These spores also like wounds in the foot because the foot is a long way from the heart, so it doesn’t have the best blood flow.
There is the rusty nail connection. The nail was lying in the dirt, thus the rust. When you stepped on it, some dirt may have been pushed into the hole in your foot. Dirt in a foot wound is a good set up for tetanus. You could get tetanus from a plastic nail as long as dirt got into the wound.
If you get a few clostridia tetani spores in your wound and the conditions are just right, they will try to grow. If they succeed in growing, they will release a toxin that paralyzes your muscles. The lock-jaw will be the least of your problems; the lock-diaphragm stops your breathing. If you have had a tetanus shot recently, you have high levels of immunity that can kill these germs before they cause trouble. If you haven’t had a tetanus shot in 5 or 10 years, we give you a tetanus shot (usually TDap) and remind your immune system to get going. Once you have had a couple of tetanus shots, you can mount an immune response in a hurry when given a tetanus booster. Your body can actually make this protection faster than the clostridia spores can grow, so you’re safe.
A tetanus shot (TDap) gives you great immunity for 5 years. Even in the presence of a dirty wound containing clostridia tetani, you are safe from tetanus.
For five to 10 years after a tetanus shot, you have partial immunity to tetanus, but it would be a race between the clostridia growing and your immune system fighting it. If the wound is clean, you don’t need a tetanus shot, as there is little or no risk of tetanus. If it is dirty (literally containing dirt), we will give you a tetanus shot, just to be safe.
The most common wound that is the source of tetanus in the U.S. is rose thorn wounds. You are gardening, so you have dirty hands, a rose thorn pokes you, and what self-respecting gardener worries about a rose thorn prick? You don’t even wash your hands. You just keep gardening. Perhaps not too surprising this can be the source of tetanus.
So get a tetanus shot (TDap) every decade or sooner for dirty wounds. Remember to promptly use soap and water to get any visible dirt out of a wound, even minor wounds. Gardeners especially – stay up on your tetanus immunizations.
Stay well,
Dr. B
