What is Tetanus?
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Clinically, tetanus is an acute intoxication caused by an exotoxin from Clostridium tetani. The bacterium usually enters through an injury like standing on a nail on the ground. That said, history of an injury may be lacking. Four types of disease manifestation are described, viz., generalised, localised, cephalic, and neonatal.
Generalised tetanus is characterised by painful muscular contractions, primarily of the main cheek and neck muscles which is known as trismus or lockjaw. Later the trunk muscles also go into painful contractions. Generalised muscle spasms are frequently induced by sensory stimuli like loud noises or bright lights.
Features of these spasms are extreme hyperextension of the body, so your head and heels are bent backward and your backbones arch forward in what is called opisthotonos, and you have a characteristic facial expression known as “risus sardonicus.”
A common first suggestive sign in older children and adults is abdominal rigidity
Infected wounds of the head and neck area can lead to cranial nerve dysfunction or cephalic tetanus.
Neonatal tetanus is known as tetanus neonatorum and is characterised by a neonate who sucks and cries well for the first few days after birth but who subsequently develops progressive difficulty and then inability to feed because of trismus which goes onto generalised stiffness with spasms or convulsions and opisthotonos.
The case-fatality rate (CFR) ranges from 10% to more than 80% depending on age, the quality of care available, and the length of the incubation period. Case-fatality rates for the neonatal disease can get higher than 80% among those with short incubation periods.
Mental retardation may occur after recovering from the neonatal disease.
The case-fatality rate is also high in the elderly and depends on the availability of high dependency critical care and resources.
Tetanus is caused by C. tetani, the tetanus bacillus, a Gram-positive bacillus, which is a common anaerobic soil bacterium. Anaerobic means it can live happily in the absence of oxygen.
In terms of diagnosis, trying to get laboratory confirmation is as useful as tits on a bull. A negative culture does not rule out the diagnosis as the organism is rarely recovered from the site of infection, and usually, antitetanus antibodies are undetectable in most cases.
Tetanus is a clinical diagnosis. While microbiologists will squeal with glee if we grow C. tetani it doesn’t really mean that much for patients with typical symptoms.
Tetanus occurs worldwide, fortunately, because of wide-spread use of a safe and effective immunisation, it is now uncommon in most industrialised countries but is more common in agricultural regions and in areas where contact with animal faeces is more likely and in places where immunisation is inadequate.
The parenteral use of illicit drugs, particularly intramuscular or subcutaneous injection, can result in individual cases and occasional circumscribed outbreaks.
In 2006, an estimated 290,000 people worldwide died, most of them in Asia, Africa, and South America. Populations in rural and tropical areas are especially at risk, and neonatal tetanus is common.
The neonatal disease is a serious health problem in many developing countries where maternity care services are limited and immunisation against tetanus is inadequate. In recent years the incidence of neonatal tetanus has declined in many developing countries because of improved training of birth attendants, hygienic confinements which is an old-fashioned way of saying having a baby, and immunisation coverage with tetanus toxoid for women of childbearing age. Despite this decline, WHO estimated in 2011 that tetanus neonatorum still caused about 61,000 deaths, mainly in the developing world.
Habitat of C. tetani
The spores of C. tetani are ubiquitous in the environment and are normal but harmless inhabitants of intestines of horses and other animals. Spores in soil or fomites contaminated with animal and human faeces can contaminate wounds of all types.
The incubation period is usually between 3 and 21 days, although it may range from 1 day to several months, depending on the character, extent, and location of the wound. Most cases occur within 14 days. In general, shorter incubation periods are associated with more heavily contaminated wounds, more severe disease, and a worse prognosis.
For tetanus neonatorum, the average incubation period is about 6 days, with a range from 3 to 28 days.
The disease is not transmitted person-to-person. The spores are usually introduced into the body through a puncture wound contaminated with soil, street dust, or animal or human faeces; through a laceration, burns, and even a trivial or unnoticed wound; or by injected, contaminated drugs illicit drugs.
Tetanus occasionally follows surgical procedures, such as circumcision and abortions performed under unhygienic conditions. The presence of necrotic tissue and/or foreign bodies favours growth of the anaerobic pathogen. Cases have followed injuries considered too trivial for medical consultation.
Tetanus neonatorum usually occurs through the introduction of tetanus spores via the umbilical cord during delivery through the use of an unclean instrument to cut the cord or after delivery by “dressing” the umbilical stump with substances heavily contaminated with tetanus spores, frequently as part of natal rituals.
Recovery from tetanus may not result in immunity; second attacks can occur and primary immunisation is indicated after recovery.
Risk groups include those with greater than usual risk of traumatic and puncture injury, especially workers in contact with soil, sewage, and domestic animals; members of the defence forces; police personnel, and others with greater than usual risk of traumatic injury; adults with diabetes mellitus; older adults who are currently at highest risk for tetanus and tetanus-related mortality; and unvaccinated women of reproductive age and their newborns.
Most newborn infants with neonatal tetanus are born to nonimmunised mothers delivered by an untrained birth attendant outside a hospital.
Prevention and management
Prevention strategies include:
Universal active immunisation with adsorbed tetanus toxoid, which gives durable protection for at least 10 years; after the initial basic series has been completed, single booster doses elicit high levels of immunity.
For children younger than 7 years, tetanus toxoid is generally administered together with diphtheria toxoid and pertussis vaccine as a triple antigen injection. In Australia, infants are immunised at 2, 4 and 6 months followed by booster doses later in the childhood and then in the teenage years. Tetanus immunisation should occur every 10 years after that.
Of course, the schedule is different for patients with relevant medical conditions, so it’s always important to consult with your own medical practitioner for specific advice.
In patients who have been completely immunised and who sustain minor and uncontaminated wounds require a booster dose of toxoid only if more than 10 years have elapsed since the last dose was given. For major and/or contaminated wounds, a single booster injection of tetanus toxoid should be administered promptly on the day of injury if the patient has not received tetanus toxoid within the preceding 5 years.
In patients who have not completed a full primary series of tetanus toxoid require a dose of toxoid as soon as possible following the wound and may require passive immunisation with human tetanus immunoglobulin if the wound is major and/or if it is contaminated with soil containing animal faeces.
Antibiotics have a limited role because the disease is an intoxication more than an infection. Antimicrobials against C. tetani may reduce production of toxin, but this does not obviate the need for prompt treatment of the wound together with appropriate immunisation. Metronidazole is the most appropriate antibiotic in terms of recovery time and case-fatality rate and should be given for 7–14 days in large doses.
Questions for readers and listeners
When was the last time you had your tetanus immunisation?
Have you ever stood on a rusty nail?
How do you feel about childhood immunisation?
Please leave your answers in the comments section of the show notes or on the Facebook page or on YouTube.
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