By Dr Lara Goldstein, MBBCh, MMED (Emergency Medicine), FCEM (SA), Cert. Critical Care (SA)

The sporeof Clostridium tetani is pervasive in the environment and leads to tetanus - an illness characterised by the acute onset of painful muscle spasm seemingly without cause. The global mortality rate of tetanus is estimated to be 30-50% but no one who has completed a primary immunisation series has ever died. The vaccine for tetanus is nearly 100% effective. Tetanus is a notifiable disease.

Clostridium tetani spores may be found in soil, manure, dust, skin, clothing and in the gastrointestinal tract in 10-25% of people. The spores release 2 toxins when they germinate viz. tetanospasmin (major toxin which enters the nervous system) and tetanolysin (non-toxic but causes damage to tissues).

Symptoms usually occur one week post-infection but can occur between 3 days and 3 weeks after exposure.

There are 4 forms of tetanus: generalised, local, cephalic and neonatal.

Generalised tetanus is the most common form featuring risus sardonicus and trismus. There may be involvement of the laryngeal muscles and the diaphragm which may compromise airway protection and ventilation. Subsequent autonomic instability is also a cause of mortality.

Local tetanus just causes muscle rigidity at the site of the wound inoculation. It may persist for months but usually resolves without negative sequelae. It may precede the generalised form.

Cephalic tetanus is a form of local tetanus due to a head wound. It can lead to cranial nerve palsies and be confused with a Bell’s palsy.

Neonatal tetanus occurs due to umbilical cord stump infection in neonates whose mothers were not previously immunised. Application of traditional poultices including cow dung also play a role in infection. Death occurs in up to 50% of tetanus cases in neonates in developing countries.

Tetanus is a clinical diagnosis. There is no benefit to laboratory or radiological tests unless an alternate diagnosis is considered more likely.

Pre-exposure prophylaxis

Pre-exposure prophylaxis should be administered according to local immunisation schedule guidelines.

Post-exposure Prophylaxis

Refer to the attached flow chart for guidance regarding tetanus vaccination and immunoglobulin administration.

Treatment

1. Prevention of further toxin release: Antibiotics kill the bacteria and therefore prevent further toxin release. Metronidazole should be used and not Penicillin G (increased risk of seizures due to inhibition of GABA and further potentiation of tetanospasmin). Metronidazole has comparable or better antimicrobial activity than Penicillin G. Tetanus toxoid immunisation should also be given as neither the disease nor the immunoglobulin conveys long-term immunity.

Surgical debridement has no benefit for tetanus. The wound responsible is commonly healed/healing at presentation. If debridement is indicated, it should be undertaken after the patient has been stabilised.

1. Neutralisation of unbound toxin: Tetanus immunoglobulin must be given within 24 hours of exposure in order to neutralise unbound toxin. Dosage is toxin-based not weight-based – 250-500IU IM is considered appropriate for both adults and children.
2. Minimisation of effects of bound toxin: Benzodiazepines (preferably short-acting e.g. midazolam) can be used for both spasms and seizures. Magnesium sulphate, 40 mg/kg followed by a continuous intravenous infusion can be considered as an adjunct but is still under investigation. Patients may need sedation, intubation and paralysis in ICU (need to monitor for seizures with an EEG if patient is paralysed).

Dr Lara N Goldstein is a Speaker at the Emergency Medicine Conference at the 2018 Africa Health Exhibition & Congress scheduled to be held from 29th to 31st May in Johannesburg, South Africa. 

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Dr Lara N Goldstein is a Specialist Emergency Physician and Intensivist at Netcare Mulbarton Hospital ICU, Division of Emergency Medicine, University of the Witwatersrand Johannesburg, South Africa