04/08/2013 04:25 EDT | Updated 06/08/2013 05:12 EDT

Tetanus: How You Catch It And Avoid Infection

tetanus bacteria
TORONTO - You do not want to get infected with tetanus.

The disease, which used to kill about 40 to 50 Canadians a year in the 1920s and '30s, is now only rarely reported. In recent years, Canada has seen, on average, only a couple of cases a year.

But doctors who have seen what tetanus does do not forgot it.

The bacteria multiply and start producing toxins that force muscles into painful contractions. One of the first places where those contractions take hold is in the muscles of the jaw — that's where tetanus's other name, lockjaw, comes from. Patients are racked with spasms.

It can take weeks and even months for the toxins to break down and the muscles to release, if they do. Between 10 and 20 per cent of tetanus cases die.

Infectious diseases specialist Dr. Allison McGeer vividly recalls the first time she saw a tetanus case. She remembers the date without needing to consult notes or a calendar. It was Nov. 1, 1981, and she was a medical intern, a doctor in training.

It was the first day in her medicine rotation and McGeer was in the emergency department. In walked a British man in his late 70s.

"He said 'I think I have lockjaw,'" McGeer recalls.

"Three hours later, he was intubated and paralyzed. And he stayed in the ICU until the end of February. I have absolutely no idea how he survived."

The disease is caused by the bacteria Clostridium tetani, which are found in soil all over the world. The bacteria form spores, a hardy casing that helps them survive.

Because the bacteria are in soil, they are also in dust, so the spores can settle on objects like the thorns of a bush or a fence. Typical tetanus stories involve gardening, which is why health practitioners aggressively promote the shots around this time of year.

"Gardening is particularly bad because you have your hands in soil.... You're more likely to injury your hands when you are gardening — which is why people focus on the gardening. Doing anything outside," McGeer says.

That's just how the British man became infected.

He had been gardening and got a splinter from a wooden railing. The fragment of wood burrowed deep into the tissue between his thumb and index finger. He had never had a tetanus shot, growing up before the vaccine was added to the complement of vaccinations given in childhood.

People who haven't been vaccinated but who have been exposed — or possibly exposed — are treated with tetanus immune globulin, tetanus antibodies taken from donated blood. But when a case progresses to the stage that the British man's had, treatment involves placing patients into induced comas to try to combat the spasms. Patients are also put on ventilators, machines that breathe for them.

"You sedate the hell out of them so they're not awake, and then every once in a while you let the paralysis lift to see if they go into spasm. And if they go into spasm, you paralyze them again and you just wait," McGeer says.

But the toxins wreak havoc on the rhythm of the heart. The British man endured tachycardia — a rapidly racing heart beat — for hours on end. That can interfere with the circulation of blood, causing organs like kidneys to go into failure.

Dr. Ian Gemmill, the medical officer of health for the health unit that serves four counties in and around Kingston, Ont., has memories of a different tetanus case. In 1985, a man from his region was walking when he got knocked over by a cyclist. His face was abraded when it scraped the ground.

When emergency room staff treat skin wounds, they will often give tetanus vaccine, just to be on the safe side. But because this man had been in the Armed Forces, health professionals assumed he had had tetanus shots at some point in his life. He had not.

"This was really a preventable case and it was kind of tragic as a result because the person ended up dying," Gemmill says.

"It's a very nasty death because one can't breathe anymore, so you have to be intubated. And then it's a question of whether or not that very tightly binding protein, which is paralyzing muscle, can be removed over time. Or can you keep the person alive long enough ... before other complications lead to death?"

Fortunately, doctors in Canada these days don't often have to struggle to keep tetanus patients alive, because a large proportion of the population has been vaccinated.

Tetanus is among the shots given in childhood. It's bundled in vaccines that protect against diphtheria, pertussis (whooping cough), polio and Hemophilus influenzae type B. Any child who has had all his or her shots will be protected against tetanus. But that wouldn't be true for children whose parents refuse to vaccinate them. Those children would all be at risk.

With some diseases, unvaccinated children are shielded to a degree because most children are vaccinated. Diseases like measles and chickenpox are much rarer these days because so many children can't catch — and therefore don't spread — these viruses. That's a phenomenon called herd immunity.

But there is no herd immunity against tetanus, Gemmill notes. Because the source of infection is the environment, the only way an individual can be protected is if he or she is vaccinated.

Adults need tetanus booster shots every 10 years to maintain the needed level of protective antibodies. For adults, the vaccine comes in a serum that also protects against diphtheria and pertussis.

"Think about tetanus this time of year, especially if you're a gardener or you're working with your hands," says Gemmill. "Because that's exactly the kind of person who might sustain a injury."