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My Mother and aunties always asked with alarm how I got even a minor scratch when I was young. If an injury was caused by anything rusty, I was to be transported immediately to the doctor for a "tetanus shot" so I would not get "lockjaw". Do injuries from rusty object cause tetanus? Is there a significant chance of contracting tetanus this way in first world countries?

Logic Knight
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  • Isn't that what vaccines are for? – AaronD Nov 24 '15 at 23:33
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    @AaronD Td/Tdap vaccine shots are really just booster shots that degrade over time. It's typically suggested that you get a new one every ~10 years or every time you receive a puncture wound, whichever happens first. – TylerH Nov 25 '15 at 18:59
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    This is not authative so I'm making it a comment. Rust does not cause infection. In the "old days" the place where you found rusty nails to step on was the barn, as the compost fumes made the nails rust loosen and fall. And the animal waste on the ground is what causes the danger of infection. So you would beware of rusty nails, but the rust is not the infective agent; meerly the cause of it falling out, and the charactization of the hazard. – JDługosz Nov 26 '15 at 08:00

2 Answers2

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Rusty or not, any contaminated object that causes an injury could result the injured person to have a Tetanus infection. And it is not just the first world countries, because Tetanus occurs worldwide.

More than a rusty nail

The New York Times has demystified the claim in a short article [1], which is good for a prompt reading. It is more than just a rusty nail for one to have a Tetanus infection.

A rusty nail will do. But the infection can come from many sources -- sewing needles, animal bites, gardening tools, splinters. Injuries that create dead skin, like burns and frostbite, can also lead to infection.

Quora has similarly short answers [2] to debunk the claim; The most upvoted answer explained well in a paragraph, albeit had misspelt the bacteria name (corrected name with emphasis mine).

It is neither the nail nor the rust that causes Tetanus.

Tetanus is caused by the infection with Clostridium Tetani, an organism that is ubiquitous and more likely to be found in dust and dirty places. If it is present on a rusty nail, it can cause Tetanus, only if the person is not immunized against it.

HowStuffWorks has explained further on the exposure of the bacteria to the people. Neither people in farms and cities are completely safe, according to its article [3], notably page 2 as quoted below.

Tetanus is caused by bacteria known as Clostridium tetani, which is commonly found in soil, dust and animal feces. Because of its presence in soil and manure, gardeners and others who work in agriculture are particularly at risk for exposure to this bacteria [...] But city-dwellers aren't completely safe -- a dusty sidewalk or street may harbor just as many bacteria.

Clostridium tetani (C. tetani)

Centers for Disease Control and Precention (CDC) explains about Tetanus and the bacteria that causes the infection in its publication, which is available as an HTML page [4] and a PDF file [5].

Tetanus is an acute, often fatal, disease caused by an exotoxin produced by the bacterium Clostridium tetani. [...]

The organism (C. tetani) is sensitive to heat and cannot survive in the presence of oxygen. The spores, in contrast, are very resistant to heat and the usual antiseptics. They can survive autoclaving at 249.8°F (121°C) for 10-15 minutes. The spores are also relatively resistant to phenol and other chemical agents.

There is no mention of "rust" found in the text of publication, which would disagree with the claim that "rusty nail wounds cause tetanus". Regardless of minor or major wounds, contamination leads to a successful infection.

Transmission is primarily by contaminated wounds (apparent and inapparent). The wound may be major or minor. In recent years, however, a higher proportion of patients had minor wounds, probably because severe wounds are more likely to be properly managed. Tetanus may follow elective surgery, burns, deep puncture wounds, crush wounds, otitis media (ear infections), dental infection, animal bites, abortion, and pregnancy.

Tetanus treatment and prevention

While Tetanus is a preventable disease [4][5], a person who has been infected should be treated immediately with human tetanus immune globulin (TIG) (or equine antitoxin) [6][7].

Tetanus is not contagious from person to person. It is the only vaccine-preventable disease that is infectious but not contagious.

One should have received Tetanus vaccine when one was younger than 7 years of age. A booster dose may be given to adults, but the amount of dose varies by whether the adult was unvaccinated or after an exposure to the infection under some circumstances [8].

References

[1] The Claim: Stepping on a Rusty Nail Can Cause Tetanus by Anahad O'Connor, Feb. 22, 2005.

[2] If you step on a rusty nail, will you really get tetanus? on Quora, asked 15 weeks ago to this date.

[3] If you step on a rusty nail, will you really get tetanus? on HowStuffWorks.

[4] Tetanus Chapter of Pinkbook: Epidemiology and Prevention of Vaccine-Preventable Diseases on CDC, 13th Edition (2015) retrieved on Nov. 24, 2015.

[5] Printer friendly version of Tetanus Chapter of Pinkbook: Epidemiology and Prevention of Vaccine-Preventable Diseases on CDC, 13th Edition (2015) retrieved on Nov. 24, 2015.

[6] Tetanus: Diagnosis and Treatment on CDC.

[7] Tetanus Immune Globulin (Injection) on National Library of Medicine - PubMed Health.

[8] Vaccines: VPD-VAC/Tetanus/main page on CDC.

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    Absolutely outstanding answer, and excellent sources – J Sargent Nov 24 '15 at 12:46
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    The reason why rusty nails are blamed, is because they are one of the few objects capable of producing a wound in such a way as to be very beneficial to tetanus. Tetanus abhors air, it cannot survive when exposed to Earth's atmosphere. So a nail, or other metal (typically rusty) buried right below the surface of the Earth provides both the ideal living conditions for the bacteria and a potential transmission vector. Couple this with a nail's ability to create deep, closed, wounds, and you have the perfect Tetanus transmission object. – Jonathon Nov 24 '15 at 13:48
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    Just to be clear, _Clostridium_ is the infectious organism; tetanus is the disease (referring to its primary symptom, spastic paralysis). – sam Nov 24 '15 at 21:17
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    I wonder what anti-vaxxer parents do when their kid gets a puncture wound … – Tom Zych Nov 25 '15 at 09:48
  • @JonathonWisnoski: Just last week I stepped on an upright rusty nail that was sticking up from a wooden board. It pierced the shoe and impaled my left foot. I went straight to the clinic for a tetanus shot. **You mention that the bacteria cannot survive when exposed to air**. Therefore in the situation that I describe, in which the nail was upright and soaked in air, was I at risk of infection? **Thank you**. – dotancohen Nov 25 '15 at 13:28
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    @dotancohen: *Definitely*, because [*C. tetani* forms spores](https://en.wikipedia.org/wiki/Clostridium_tetani) to survive in hostile aerobic environments, only activating when in a favorable environment such as your foot. – Tom Zych Nov 25 '15 at 15:02
  • @TomZych: Thank you. I actually had just read that article but it was not mentioned there that the spores activate in such environments. Of course, that may be so clear to biologists that it doesn't need to be explicitly stated! – dotancohen Nov 25 '15 at 15:20
  • @dotancohen Well like this answer points out, there really is not anything special about nails. Being out in the open, means its not anymore likely to have Tetanus than a prickle bush. If the wound was deep, you might want to have it cleaned out (and the doctor is very likely to give you a Tetanus shot, but mostly just because "why not?") I once had a rusty metal rod shoved up my armpit and the doctors did not bother with a T. shot. – Jonathon Nov 25 '15 at 17:02
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    Animal bites are quite famous for causing Tetanus indeed. Getting hit during a traffic accident and scraping over the asphalt will work as well. – Mast Nov 26 '15 at 10:20
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    Yeah, the thing about nail wounds is that they don't typically bleed much (and bleeding carries away contamination), plus the cut is not open to permit it to be easily washed. And often a nail wound is considered "minor" and not seen to require medical treatment. So this creates the perfect conditions to introduce the bacterium into the body and keep it from being subsequently removed. – Daniel R Hicks Nov 28 '15 at 07:42
  • @DanielRHicks: That was exactly my experience. There was no bleeding, and even though I could clearly identify the hole by touch when I removed my shoe immediately for inspection, by the next day it was completely hidden from outside observation (still hurt, though). I cannot imagine how the would would have been cleaned without surgery. – dotancohen Nov 28 '15 at 10:13
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Tetanus toxin, which has been given the scientific name tetanospasmin, is created when the bacterium Clostridium tetani divides and grows. C. tetani cannot divide in an oxygenated environment, but as a piece of iron flakes off and rusts, it robs the surrounding environment of oxygen. This is the easiest way for C. tetani to reproduce and create toxins (source 1). It is the exposure of an iron surface, not the amount of rust, which makes it possible for C. tetani to become potent, but rust is obviously a danger sign.

Tetanus toxin is one of the most potent neurotoxins in the world. If your skin is broken by contact with rusting iron and active C. tetani spores enter the bloodstream, the toxin will start work immediately and it is indeed worth a hospital visit. Lockjaw, caused by the toxin binding itself to more vulnerable parts of the nervous system, has been known as one of the first signs of tetanus poisoning since ancient times (source 2).

Sources

  1. Demain AL, Gerson DF, Kole M, Fang A. "The role of reduced iron powder in the fermentative production of tetanus toxin." Appl Microbiol Biotechnol. 2006 Nov;73(1):55-9. Epub 2006 Apr 19.

  2. J M Pearce. "Notes on tetanus (lockjaw)." J Neurol Neurosurg Psychiatry. 1996 Mar; 60(3): 332.

Avery
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    That first source does not seem to be about growth of tetanus in the natural environment; it's about how to efficiently produce tetanus toxin, which is used to create vaccines. Do you have any source you could use instead that focuses on tetanus growth in non-cultivated conditions? – paradisi Nov 24 '15 at 10:26
  • I wasn't able to find anything, but perhaps this study can guide a common sense judgment that rust indicates deoxygenation at work. I don't disagree with the other answer saying that the bacteria is found in other places as well. – Avery Nov 25 '15 at 03:25