What is tetanus?

What is Tetanus?

Tetanus is an acute, often fatal, noncommunicable disease caused by the potent neurotoxin tetanospasmin, which is produced by the anaerobic bacterium Clostridium tetani when its spores germinate in oxygen-poor wounds or necrotic tissue. 1

The Causative Organism

• Clostridium tetani is a ubiquitous, spore-forming, Gram-positive anaerobic bacillus found worldwide in soil, animal excrement, and the intestines of animals and humans 2, 1
• The spores are extremely hardy and can survive in the environment indefinitely, entering the body through any breach in the skin or mucous membranes 1
• Germination occurs only under anaerobic or hypoaerobic conditions, such as those found in deep puncture wounds, blunt trauma with necrotic tissue, burns, surgical sites, or contaminated umbilical stumps in newborns 2, 1

The Pathophysiology

• Once germinated, the vegetative bacilli multiply and produce tetanospasmin, an extremely potent exotoxin that binds irreversibly to neural tissue 1, 3
• Tetanospasmin prevents the release of inhibitory neurotransmitters (particularly GABA) in the spinal cord, brainstem motor nuclei, and brain, resulting in unopposed muscle contraction 1
• This irreversible binding is the critical pathophysiologic feature—once toxin binds to neurons, it cannot be reversed, which is why treatment focuses on neutralizing circulating toxin before it reaches neural tissue 1

Clinical Manifestations

• The disease typically presents with trismus (lockjaw) as the initial symptom, followed by generalized rigidity and painful tonic spasms of skeletal muscles 2, 3
• A characteristic grayish adherent membrane in the pharynx (described for diphtheria, not tetanus) is NOT a feature of tetanus 2
• Muscle stiffness progresses from the jaw and neck to become generalized, with paroxysmal contractions that can impair respiratory function 2, 3
• Severe cases develop glottic spasm, respiratory failure, and autonomic instability (dysautonomia) that can result in death 2, 3

Temporal Course

• The incubation period ranges from 3 to 21 days (median: 7 days), with extremes of 1 day to several months 1, 4
• Shorter incubation periods correlate with more severe disease and worse prognosis, while longer incubation periods occur with injuries furthest from the central nervous system 4
• The acute disease course is typically intense for at least 4 weeks before subsiding 4
• The convalescent period is protracted, and long-term neurologic sequelae or intellectual and behavioral abnormalities may follow recovery 4

Mortality and Prognosis

• Without high-quality medical care, mortality approaches 100% 5, 4
• Even with modern intensive care, the case-fatality rate remains 10-20% (80-90% survival rate) 5
• In the United States, the case-fatality ratio has improved from 18% (1998-2000) to 8.0% (2001-2016) 5
• Mortality is highest in infants and the elderly 5, 4

Key Epidemiologic Features

• Tetanus is unique among vaccine-preventable diseases because it is noncommunicable—it is not transmitted person-to-person 2
• The disease occurs almost exclusively among persons who are unvaccinated, inadequately vaccinated, or have unknown vaccination histories 2, 4
• Natural immunity does not develop from tetanus infection, so recovered patients must complete a full primary immunization series 4
• In the United States, tetanus is primarily a disease of older adults, with at least 40% of persons aged >60 years lacking protective antibody levels 2

Critical Clinical Pitfall

• Serologic tests indicate that immunity to tetanus toxin is NOT acquired naturally—having the disease does not protect against future episodes, making vaccination after recovery essential 2, 4