Why is it so dangerous to step on a rusty nail?

In the 5th century, the renowned Greek physician Hippocrates, who is credited with creating the Hippocratic Oath, encountered a troubling case during a sea voyage. The ship's captain was gravely ill with symptoms that included severe muscle spasms, jaw clenching, and a stiffness that affected his neck and spine. Despite Hippocrates' thorough documentation of these symptoms, he was unable to identify or treat the affliction. Tragically, the captain died six days later. This early account is now recognized as one of the first documented cases of tetanus. Fortunately, contemporary medical practices have advanced significantly, enabling physicians to effectively manage this once-mysterious infection.

Tetanus, caused by the bacterium Clostridium tetani, is distinct from other bacterial infections like tuberculosis or strep throat because it is not transmitted from person to person. Instead, the bacteria enter the body through wounds such as cuts or abrasions. The association between tetanus and rusty objects, such as nails or scrap metal, stems from the fact that these items can cause injuries where the bacteria can thrive. However, the link to rust is more incidental than direct. Clostridium tetani bacteria are commonly found in soil, animal manure, and decaying plant matter. These bacteria can endure for years in the form of spores, surviving extreme conditions of heat and dryness.

When organic materials such as soil or manure are disturbed, they may expose metal objects that have rusted over time. A person who injures themselves on such objects may thus increase their risk of tetanus infection. Rusty metal can cause deep, jagged wounds with areas of dead tissue, creating an environment where the bacteria can flourish. Once the spores enter the body, they begin to germinate, producing several toxins, including the highly dangerous tetanus toxin. This toxin is absorbed by nerve endings and transported to the brain and spinal cord, where it disrupts the function of interneurons. Interneurons typically help regulate muscle actions, from complex movements like kicking a ball to simple ones like breathing.

The tetanus toxin impedes the neurotransmitters that interneurons release, resulting in uncontrollable muscle contractions and spasms. Symptoms generally start within 7 to 10 days after infection, beginning with general discomfort, difficulty swallowing, and lockjaw. The head and neck are usually affected first. As the toxin progresses, it causes increased rigidity in larger muscle groups, which can lead to severe back arching. If untreated, the spasms can escalate, ultimately affecting the muscles involved in breathing and leading to suffocation within 72 hours from the onset of symptoms. Without prompt treatment, the survival rate for tetanus is very low.

Fortunately, modern medicine has developed effective strategies for managing tetanus. The treatment protocol starts with cleaning the infected wound and administering antibiotics to eliminate the bacteria and halt further toxin production. An antitoxin is then given to neutralize any tetanus toxin that has not yet affected the central nervous system. The patient will also receive supportive care over several weeks, which may include muscle relaxants to alleviate spasms and ventilatory support to prevent breathing difficulties.

In Hippocrates' time, there were no effective treatments, and patients could only hope for the best. Today, the focus is on prevention. The development of tetanus vaccines in the early 1920s has been a crucial advancement in preventing the disease. Vaccination schedules typically start at two months of age and continue with booster shots until around age 12. Despite these efforts, tetanus still poses a significant threat, particularly in low- and middle-income countries where vaccine access is limited, such as in South Asia and sub-Saharan Africa. Each year, over 20,000 infants die from tetanus, often due to unvaccinated mothers who can transmit the bacteria to their newborns through the umbilical stump. Vaccinating mothers during pregnancy can help reduce this risk.

Tetanus remains a serious health concern, emphasizing the importance of vaccination and wound care. Ensuring that you and your loved ones are up-to-date with tetanus vaccinations and taking appropriate measures to clean and treat wounds can help prevent this dangerous infection, whether caused by a rusty nail or an ancient ship anchor.