Tetanus

Tetanus, or lockjaw, is a bacterial infection caused by Clostridium tetani, characterised by muscle spasms and potentially fatal complications.

This infection typically starts with muscle spasms in the jaw and progresses to the rest of the body.

Signs and Symptoms

Tetanus often begins with mild spasms in the jaw muscles, known as lockjaw or trismus. These spasms can spread to the facial muscles, causing risus sardonicus, and other muscle groups including the chest, neck, back, and abdomen. Severe spasms can lead to opisthotonus (arching of the back) and respiratory problems. Other symptoms include fever, sweating, headache, difficulty swallowing, elevated blood pressure, and a rapid heart rate. Muscle spasms can be intense enough to cause fractures and muscle tears.

Incubation Period

The incubation period ranges from 3 to 21 days, typically averaging around 10 days. The farther the injury site from the central nervous system, the longer the incubation period, with shorter periods leading to more severe symptoms. In neonatal tetanus, symptoms appear 4 to 14 days after birth.

Types of Tetanus

• Generalised Tetanus: The most common form, presenting with a descending pattern starting with lockjaw, then facial spasms, followed by neck stiffness, difficulty swallowing, and muscle rigidity.
• Neonatal Tetanus: Affects newborns, usually due to infection of the umbilical stump. Common in developing countries, it causes significant neonatal mortality.
• Local Tetanus: Causes persistent muscle contractions near the injury site. It is generally milder and less fatal.
• Cephalic Tetanus: The rarest form, affecting the muscles and nerves of the head. It has a higher fatality rate due to potential progression to generalised tetanus.

Cause

Tetanus is caused by the bacterium Clostridium tetani, which is commonly found in soil, dust, and animal faeces. The bacteria enter the body through breaks in the skin, such as puncture wounds. They thrive in anaerobic environments, producing toxins that interfere with normal muscle contractions.

Pathophysiology

The tetanus neurotoxin binds to the presynaptic membrane of the neuromuscular junction and is transported to the central nervous system. It inhibits the release of neurotransmitters GABA and glycine, leading to uncontrolled motor neuron activity and muscle spasms. The toxin is composed of a heavy chain and a light chain, each playing a role in the binding, internalisation, and action of the toxin within neurons.

Diagnosis

Diagnosis is based on clinical presentation, as there are no definitive blood tests for tetanus. The "spatula test" can be used, where touching the posterior pharyngeal wall with a soft-tipped instrument leads to an involuntary jaw contraction in positive cases.

Prevention

Vaccination with tetanus toxoid is the primary preventive measure. The CDC recommends a booster every ten years. For those with significant wounds and uncertain vaccination history, both vaccination and tetanus immune globulin are recommended.

Treatment

Treatment includes tetanus immune globulin, antibiotics like metronidazole, and muscle relaxants such as diazepam. Severe cases may require mechanical ventilation and intensive care. Nutritional support is also very important, with high-caloric and high-protein intake to support recovery.

Epidemiology

Tetanus remains a global health issue, particularly in developing countries. In 2013, there were approximately 59,000 deaths worldwide. In the United States, tetanus cases are rare, with most occurring in unimmunized individuals.

In Animals

Tetanus affects goats and sheep, causing symptoms like extended head and neck, stiffness, lockjaw, and spasms. Death often results from respiratory paralysis.

History

Tetanus has been recognised since ancient times. Significant milestones in understanding and treating tetanus include the isolation of the bacterium by Kitasato Shibasaburō in 1891 and the development of the tetanus toxoid vaccine in 1924.

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Self-assessment MCQs (single best answer)

What bacterium causes tetanus?

What is the common initial symptom of tetanus?

Which form of tetanus primarily affects newborns?

How does the tetanus toxin affect the body?

What is the primary preventive measure against tetanus?

During which period do tetanus symptoms typically appear after infection?

What is the purpose of the "spatula test" in diagnosing tetanus?

What is the role of tetanus immune globulin in treating tetanus?

Which of the following is NOT a symptom of tetanus?

In which environment do Clostridium tetani bacteria thrive?