How does Tetanus actually lock your jaw together?

Tetanus, a dreaded bacterial infection, used to be a terror of the world. Frequently fatal, its first sign was the stiffening of the jaw that rendered the sufferer mute. But how does a bacterium lock a person's jaw shut, anyway?

Of all the ways for someone in the pre-vaccination age to go, tetanus was among both the most commonplace and the more horrible. It could strike anyone, from a man who shaved with a razor blade to a hobby gardener or woodworker, to a lady working at her needlepoint. Over time, it became associated with rusty metal. Actually, the cause of tetanus was, and is, everywhere. It's a bacteria that creeps through the soil, clings to surfaces, and swims through the intestines of animals and even humans. Because it's anaerobic, it thrives in environments without oxygen. This might be why it's associated with rust — the rough surface gives it a place to cling and the oxidization of the material removes that pesky oxygen. Rusty metal, such as barbs and nails, also makes for deep puncture wounds with interiors that have limited exposure to oxygen.

How does Tetanus actually lock your jaw together?

Once it's in the bloodstream, the bacteria, Clostridium tetani, does the two most destructive things it can do; multiplies and dies. Between the two, dying is the worse offense. Many bacteria produce toxins that have certain functions, fighting off external threats or maintaining internal order. Exactly what function the tetanus toxin performs in the Clostridium tetani is as-yet unknown. When the bacteria dies in the outside world, the toxin harmlessly seeps into the ground to decay. When the bacterium dies in the body, it travels through the nervous system as one of the more horrible neurotoxins out there.

Muscles only catch our attention when they're engaged. Relaxation, it seems to us, is the default state of a muscle. The tetanus toxin shows that this isn't necessarily so. Once a muscle is engaged, the body releases a chemical transmitter called GABA to inhibit further contraction of the muscle. The toxin released by the tetanus bacterium stops the release of GABA. The muscles experience continual contraction.

How does Tetanus actually lock your jaw together?

When there was no treatment or vaccine for tetanus, it might have been kinder if this happened to all the muscles in the body. The heart would seize up, and the victim would be dead relatively quickly. But not all muscles undergo the same process of deliberate stimulation and relaxation. Only the skeletal muscles, the muscles under our conscious and voluntary control, are subject to tetanus.

So while the mind keeps functioning and the heart keeps beating, untreated tetanus victims undergo muscle spasms that can half-smother them, make them seize backwards so their body forms an arch, and cause their own muscles to snap their own bones. The first symptoms of tetanus are in the most delicate, and often used, voluntary muscles. The jaw and the facial muscles first stiffen, then lock, and then start seizing. This is why the illness acquired the famous nickname, lockjaw.

Today, in areas where most people are given regular vaccinations for tetanus, the number of cases per year is fairly small. Where access to vaccines is limited, there are still terrible cases of neonatal tetanus. The bacteria is prolific enough that it's doubtful that tetanus will ever be eradicated, so get yourself jabbed in the arm, so you can walk around the world and not worry too much about stepping on rusty nails.

Image: Graham Crumb

Via NCBI, Medicine Net, Medical News Today.