Tetanus

This disease is notifiable in the UK under the Public Health (Infectious Diseases) Regulations 1988.

Tetanus is the result of infection with Clostridium tetani, a spore-forming Gram-positive obligate anaerobe. It was first described by Hippocrates in the 5th century BC.

Spores are found in virtually all soil, particularly soil rich in manure, but also in house dust and both animal and human faeces.
Spores can enter even the smallest wound and in anaerobic conditions found in necrotic tissue, active infection or the presence of a foreign body, produces tetanospasmin, a powerful exotoxin. This spreads via lymph and blood, and is transported up the nerves, binding irreversibly to neurons, and preventing inhibition of motor reflex responses to sensory stimuli.
This results in the characteristic muscle spasms (severe enough to tear muscles, cause long bone fractures or spinal compression fractures) and rigidity.

Incidence and mortality

• Rare in the UK approx. 10 cases/year, i.e. 0.20 per million.¹
• Largely a disease of the developing world and the poor, where there is inadequate vaccination, neonatal tetanus causing 23-75% of neonatal deaths. Killed 277,400 people worldwide in 1997.²
• Mortality in the untreated up to 45% (66% in neonates), with treatment <10%, the rate in those who have received 1-2 doses of vaccine previously being approximately half that of the unvaccinated.

Risk factors

• Age >60 years, lack of immunisation, poverty, drug addiction.
• Wounds contaminated with garden soil or manure and those caused by rusty metals are particularly dangerous.
• Can also complicate burns, ulcers, gangrene, snakebite, frostbite, otitis media, septic abortion, childbirth.
• Can also occur following IM injections in surgery.
• Tetanus neonatorum is associated with poor obstetric techniques. This is particularly the case with the practice of applying cow dung or clarified butter to the cut surface of the umbilical cord, in both Africa and India.³

Incubation period is on average 7 or 8 days but can range from 1 day to 2 months. Shorter the incubation period the worse the severity.
15-25% of cases show no evidence of recent wounds.
Clinically 3 forms recognised:

• Generalised tetanus (80%); usually a descending pattern after prodromal fever, malaise and headache:
  • Trismus (lockjaw, associated later feature: risus sardonicus, a grin-like expression from fixed facial muscle spasm)
  • Neck stiffness (which may develop into opisthotonus: arched body with hyperextended neck)
  • Swallowing difficulties
  • Abdominal muscle rigidity
  • Muscular spasms (initially reflexive, then spontaneous).
  Neonatal tetanus is a form of generalised tetanus in the newborn lacking passive immunity from a non-immune mother, infected usually via the umbilical stump through lack of antiseptic practice and application of "local remedies" (see above). Presents with inability to suck, irritability, grimaces, and rigidity.
• Local tetanus; uncommon, may precede generalised tetanus, but generally self-limiting illness with painful muscle spasms localised to the site of injury.
• Cephalic tetanus; usually secondary to otitis media or head injury, exhibiting cranial (especially facial) nerve palsies, and progressing to the generalised form if untreated.

Complications in severe generalised tetanus:

• Aspiration pneumonia
• Laryngospasm, which may lead to asphyxia
• Fractures from sustained contractions and convulsions
• Respiratory embarrassment with tachypnoea, and intermittent apnoea
• Autonomic nervous involvement leading to hypertension, dysrhythmias and cardiac arrest
• Tetanic seizures mimicking epilepsy, frequency and severity related to severity of illness, and indicate poor prognosis
• Pulmonary embolus particularly in drug abusers and the elderly.

No specific diagnostic laboratory test, diagnosis made clinically.
Spatula test useful: touching the back of the pharynx with a spatula elicits a bite reflex in tetanus, instead of a gag reflex.

Tetanus infection does not confer immunity, and immediate vaccination (inactivated tetanus toxoid) is too slow to address current infection.
Antibiotic prophylaxis against tetanus in wound management is not indicated. Active infection should be treated appropriately.

• Clean minor wounds:
  • >3 doses vaccine: no immunoglobulin, no vaccine, unless >10yrs since previous dose, and complete 5 dose schedule.
  • Unknown or <3 doses vaccine: no immunoglobulin, give vaccine, and complete 5 dose schedule.
• All other wounds:
  • >3 doses vaccine: no immunoglobulin (unless particularly high risk wound, eg contaminated with manure), no vaccine unless >5yrs since previous dose, and complete 5 dose schedule.
  • Unknown or <3 doses vaccine: give immunoglobulin, give vaccine, and complete 5 dose schedule.

Active immunisation is central to prevention, given as part of "triple vaccine", followed by boosters at school entry and leaving, 5 doses likely to confer lifelong immunity.⁵

• An additional booster may be given to travellers to areas where medical attention may be unavailable,(and likely to sustain at-risk injury) if last dose >10yrs ago, even if completed 5 dose schedule.
• Local adverse reactions to vaccine are common, but severe local reactions are usually only seen in those with high antitoxin levels.
• Rarely severe systemic reactions do occur, and there is an association with brachial neuritis and Guillain-Barre syndrome.

The muscle stiffness and ankle clonus can last for months after recovery and significant weight loss is always seen.
Signs that are significantly associated with increased mortality are⁶:

• Older age (especially > 60 years)
• Shorter duration of symptoms - trismus, rigidity and dysphagia
• Severe disease at presentation
• Shorter period of onset.