Tetanus is caused by the Gram-positive, spore-forming, obligate anaerobe Clostridium tetani. This bacteria are found worldwide, distributed in the soil.

Tetanus occurs when a wound is contaminated by C. tetani in non-immunized individuals. The toxin tetanospasmin released by this bacteria is a potent neurotoxin, affecting neuromuscular junctions and the sympathetic nervous system, causing muscle spasm and autonomic dysfunction. The mechanism of action of the tetanus toxin is that it inhibits inhibitory neurones, preventing the release of inhibitory neurotransmitters such as GABA, thus allowing a state of tetany to result from unopposed action.

Spasm of the facial muscles produces the characteristic grinning expression called risus sardonicus. Lockjaw is caused by masseter muscle spasm. Spasms are precipitated by noise, movement and light. Untreated, the frequency of spasms increase. Respiration becomes difficult because of laryngeal spasm. Dysphagia and urinary retention result from oesophageal spasm and urethral spasm. Arching of the back and neck (opisthotonus) may occur. There may be tachycardia, a labile blood pressure, sweating and cardiac arrhythmias because of the autonomic dysfunction.

Death results from respiratory arrest, cardiac arrest, aspiration, hypoxia or exhaustion.

Diagnosis: clinical.

Treatment: Prevention is preferable in ALL cases. Antibiotics and antitoxins should be given. Spasms should be controlled with diazepam. Active immunization should be commenced after recovery as immunity from an attack of tetanus is incomplete.

Prevention: Everyone should be immunized regardless of age. Tetanus immunization is now standard for childhood immunizations. Boosters should be given at 5 or 10 year intervals. For any individual presenting with a potentially dirty wound, a booster dose should be given if they do not remember when they had an injection of the tetanus toxoid.

note: vaccination against tetanus does not provide immunity against the bacterium C. tetani, but it does provoke the immune system to react against the tetanus toxin that is produced, rendering it harmless.