Why should you worry about tetanus when you hurt yourself with something rusty?
In: Biology
Actually, you dont have to worry. The bacteria that cause the tetanus live commonly in the soil. They can invade your body through a puncture/slash or any kind of wound. The object causing the wound being a rusty one is just a myth.
It’s not the rust that’s the problem, it’s that something being rusty means it’s likely been sitting in the open for quite some time and has all sorts of bacteria on it. So it’s more likely that the bacteria which causes tetanus is going to be present than if you hurt yourself with a freshly-cleaned kitchen knife, for instance.
Because it’s caused by a bacterium that enters your body in the form of “spores” that ripen to the full (toxin producing) bacterium once they entered your body.
Rusty metal is just a good place to cut yourself on something that can hold a lot of dirt (including these spores). A non-rusty piece of metal is smooth and so spores are washed off by rain easily.
There are many ways to get tetanus into wounds without rusty metal though
You shouldn’t worry too much if your tetanus vaccinations are up to date (usually every 10 years). Otherwise, yes, see a doctor – once set in tetanus is a horrible way to die. The bacteria lives in anaerobic environments – without oxygen – so either soil or other places where it’s protected from air; and often that would be the places where objects that can puncture your skin have already rusted (like metal nails). But if you have open wounds or sores, you don’t need a metal object, just contact with soul is enough.
Rust doesn’t cause Tetanus, the bacteria Clostridium tetani does.
Because C. tetani is a type of anaerobic bacterium, it lives and grows in an environment that lacks oxygen. For example, the surface of a rusty nail is a perfect environment to host endospores in part because atmospheric oxygen reacts with iron to form iron oxide. The rusting process binds the oxygen to iron in such a way as to aid in the creation of an anaerobic environment within the layers of surface rust.
**EDIT: Sorry, I felt I needed to add an edit based on some of the other comments in this ELI5 re rusty nails.**
Clostridium tetani bacteria is ubiquitous outdoors. It is an organism that feeds on dead things; it decomposes plant and animal matter through several fermentative pathways and is part of a massive microbiome that makes up soil. The Clostridia bacteria will grow and multiply in an environment that is low in oxygen, wet, dark, and surrounded by plant or animal matter.
Now take a moment to imagine what a nail is typically pounded into.
Yup, C. tetani eats and grows in decomposing wood. So, imagine that nail hammered into a fence post and left outdoors exposed to the rain. Endospores of C. tetani will be blown around as dust from the soil and act like little seeds that will land in the nooks and crevices around the nail head. The spores will germinate and then work their way into the wet cellulous rich environment surrounding the nail. The iron in the nail will react with atmospheric oxygen to create an anaerobic environment and the bacteria will multiply and then sporulate creating many more spores. The pits and rough scale on the nail can act like a sponge to hold spores of C. tetani. The spores are hearty and are not killed by exposure to the air.
So if you ever do step onto a nail, ask yourself what it may have been hammered into before and if it may actually be a hypodermic petri dish for C. tetani
Tetanus is a soil bacteria, but significantly it’s anaerobic, and dies in the presence of oxygen. It can live in mud and shit, but it really needs to be isolated from the air.
The thing about rusting metal is that the metal eats any oxygen in the water in its immediate surroundings, so it provides a much more portable anaerobic environment for the bacteria to travel around on. Instead of needing to be buried half an inch deep in unaerated soil, it can live in a thin film of mud on the surface of a rusty nail or pitchfork.
The other thing you need to know is that the kinds of wounds that are prone to tetanus infection are dirty puncture wounds. A slash or cut gets lots of blood flow (with nicely oxygenated blood), and any soil/etc in the wound is easily washed out.
But get a muddy nail in the sole of your foot, or stab yourself with a garden implement or something…. and now it’s got a dark little hole to live in, with the dirt in the wound blocking the blood flow, hard to clean out, and likely to just get bandaged up – making itself a nice little pocket of dying cells giving up their nutrients and further cutting off oxygenation of the tissues as the bacterium releases its toxins to kill more cells…
Yeah.
Important to say that tetanus is a very dangerous disease caused by bacterias and can kill. Hard to spread, but quite deadly and the infection has no cure. The treatment is focused on symptoms.
That’s the main reason why we should worry.
But it has vaccine.
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