Tetanus (“lockjaw”) results from poisoning by a potent toxin produced by Clostridium tetani, a ubiquitous bacterium that forms hardy, long-lived spores in soil, dust, and animal waste.
Clostridium spores usually enter the body through a wound; if conditions are favorable (i.e., a low-oxygen environment) the spores germinate and multiply. The toxin (tetanospasmin) is a metabolic byproduct of bacterial growth.
The incubation period between infection and onset of symptoms ranges from 2 to 50 days, with an average of 5 to 10 days. Once tetanospasmin binds to membranes at nerve synapses—where it prevents the release of inhibitory neurotransmitters—it cannot be neutralized.
Worldwide, tetanus causes one-half to one million deaths annually, mostly in newborns and young children. In developing countries, infection often occurs via the umbilical cords of newborn infants (tetanus neonatorum) or in the wombs of recently-delivered mothers (maternal tetanus). Disease incidence is directly related to the immunization level in a population.
In the US, fewer than 50 tetanus cases occur annually, due to widespread immunization programs and proper wound management. Because immunity wanes over time, over one-half of elderly Americans have inadequate antibody levels, and this population accounts for up to 1/2 of cases. Most of the remainder occur in inadequately immunized persons between the ages of 20 and 50. (The Merck Manual, 18th Edition. 2006:1503-1506)
Risk Factors for Tetanus
Risk of tetanus increases in situations where contamination with soil, dust, or feces is more likely:
- Burns
- Surgical wounds
- Deeply-penetrating or dirty wounds
- Injection drug abuse
- Lack of immunity
- Home birth (i.e., inadequate instrument sterilization or otherwise unsterile conditions)
Different Types of Tetanus
Three main classifications of tetanus have been used in clinical settings, but they often overlap because tetanospasmin moves readily through the bloodstream and along motor nerves:
- Generalized tetanus: affects all skeletal muscles. The most common and most severe form of tetanus (neonatal tetanus is a subtype of generalized tetanus)
- Localized tetanus: characterized by muscle spasms at or near the site of the infected wound
- Cephalic tetanus: affects one or several muscles of the face. May follow head injury or ear infection; usually develops rapidly
Signs and Symptoms of Tetanus
Early, nonspecific complaints (fever, sore throat, chills, headache, restlessness, and body aches) are followed by progressively severe symptoms and signs:
- Muscle stiffness
- Painful muscle spasms, including trismus (difficulty opening jaw), risus sardonicus (fixed smile and elevated eyebrows), and opisthotonos (severe spasm of abdominal, neck and back muscles); spasms are often precipitated by minor environmental disturbances (drafts, noises, etc.) and can be severe enough to fracture bones
- Urinary and fecal retention secondary to sphincter spasm
- Profuse sweating
- Hyperreflexia
- Cardiac dysrhythmias
Respiratory failure is the most common cause of death; abdominal and chest wall rigidity and diaphragmatic spasm lead to asphyxiation. Mental status usually remains clear, although coma may intervene following prolonged spasms.
Treatment for Tetanus
Treatment is supportive. Spasticity may persist for weeks in survivors.
Maintaining ventilation is a mainstay of treatment. This may require the use of drugs to temporarily paralyze patients while they are maintained on ventilators. Otherwise, three overarching principles guide therapy:
- Prevent further toxin production by cleaning the wound and administering antibiotics
- Neutralize non-fixed toxin with tetanus toxoid and tetanus immune globulin (injected into different sites)
- Minimize the effects of toxin that has already entered the central nervous system (i.e., administer medications to control spasm, rigidity, and seizures)
Prevention of Tetanus
Adequate immunization, including updating every 10 years, is the key to preventing tetanus. Meticulous wound care is also important.
Any infection-prone injury should prompt a visit to a medical professional, ideally within 72 hours. Vaccination can be administered based upon wound type and immunization history.
