Tetanus is an acute disease manifested by skeletal muscle spasm and autonomic nervous system disturbance. It is caused by a powerful neurotoxin produced by the bacterium Clostridium tetani
Causes
- C. tetani is an anaerobic, gram-positive, spore-forming rod whose spores are highly resilient and can survive readily in the environment throughout the world.
- Spores resist boiling and many disinfectants.
- C. tetani spores and bacilli survive in the intestinal systems of many animals, and fecal carriage is common. The spores or bacteria enter the body through abrasions, wounds, or (in the case of neonates) the umbilical stump. Once in a suitable anaerobic environment, the organisms grow, multiply, and release tetanus toxin, an exotoxin that enters the nervous system and causes disease.
- Superficial abrasions to the limbs are the most common infection sites in adults.
- Deeper infections (e.g., attributable to open fracture, abortion, or drug injection) are associated with more severe disease and worse outcomes.
- In neonates, infection of the umbilical stump can result from inadequate umbilical-cord care; in some cultures, for example, the cord is cut with grass or animal dung is applied to the stump.
- Circumcision or ear-piercing also can result in neonatal tetanus.
- A foreign body in a wound, such as a nail or splinter
- A history of immune-suppressing medical conditions
- Infected skin lesions in people living with diabetes
Pathogenesis
Bacteria produce tetanus toxin (tetanospasmin) can cause tetanus. Tetanus toxin is intra-axonally transported to motor nuclei of the cranial nerves or ventral horns of the spinal cord. Tetanus toxin’s escapes normal lysosomal degradation.
Tetanus toxin prevents neurotransmitter release and effectively blocks inhibitory interneuron discharge. The result is unregulated activity in the motor nervous system. The autonomic system accounts for the characteristic features of skeletal muscle spasm and autonomic system disturbance. The increased circulating catecholamine levels in severe tetanus are associated with cardiovascular complications.
Clinical manifestations
- Mild form of local tetanus, only isolated areas of the body are affected and only small areas of local muscle spasm may be apparent.
- If the cranial nerves are involved in localized cephalic tetanus, the pharyngeal or laryngeal muscles may spasm, with consequent aspiration or airway obstruction, and the prognosis may be poor.
- Muscles of the face and jaw often are affected first, presumably because of the shorter distances toxin must travel up motor nerves to reach presynaptic terminals.
- Trismus (lockjaw)
- Muscle pain and stiffness
- Back pain
- Difficulty swallowing.
- In neonates, difficulty in feeding is the usual presentation
- As the disease progresses, muscle spasm develops. Generalized muscle spasm can be very painful. Commonly, the laryngeal muscles are involved early or even in isolation. This is a life-threatening event as complete airway obstruction may ensue. Spasm of the respiratory muscles results in respiratory failure.
- High blood pressure
- Low blood pressure
- Rapid heart rate
- Fever
- Extreme sweating
Diagnosis
- Doctors diagnose tetanus based on a physical exam, medical and vaccination history
- Culture of C. tetani from a wound provides supportive evidence.
- Serum anti-tetanus Ig G also may be measured