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Home , Clostridium tetani

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Tetanus: an ever-present risk

Christopher Brightman, Consultant Microbiologist (retired); Locum GP, Lincoln CNRI/Science Photo Library was recognised as far back as the 5th century BC, when it was first described by Hippocrates. Today, immunisation has reduced the incidence of tetanus infection, but the responsible remains active in soil and manure. Although most people in the UK are covered by immunisation, the elderly and some immigrants, may be at risk.

he word tetanus comes from the TGreek tetanos, meaning ‘stretched’ or ‘rigid’ in regards to a muscle spasm. Though tetanus must have existed for Figure 1. It is the potent produced by millennia, the antiquity of the disease tetani that causes the characteristic spasms of tetanus is not known as it does not leave characteristic changes in skeletal the paintings and sketches produced Tetanus spores are present in the remains. Hippocrates (ca. 460–ca. 370 by Sir between 1809– faeces of horses, and have also been BC) recognised the disease, and its 1815. During the Peninsular War of detected in human faeces. The association with wounds has been 1808–1814, 13 out of every 1000 advent of the motor car, and the known for centuries. wounded soldiers developed tetanus. decline in the use of horses for The German Jewish physician This fell to 2 per 1000 during the transport, contributed to the fall in Arthur Nicolaier, in 1884, produced Crimean War of 1853–1856, but rose the incidence of tetanus in both tetanus in mice by injecting them with to 1 in 100 during the first two months civilian and military life. garden soil. He saw a in the of the First World War. However, the Dominique Jean Larrey (1766– pus from these animals which he incidence fell to 1.47 per 1000 after the 1842), surgeon to Napoleon I, assumed was the cause of the introduction of passive immunisation. recommended that wounds should disease, but was not able to isolate it Active immunisation against be cauterised to prevent tetanus. He in culture. In 1889, Japanese physician tetanus became available in about also recommended amputation to and bacteriologist Kitasato 1926, as a result of which the prevent tetanus in soldiers who had a Shibasaburo isolated the tetanus incidence of tetanus among wounded wound in the distal part of a limb. bacillus, and showed that it could only soldiers fell. The incidence of tetanus However, the effective treatment of grow in the absence of oxygen. among troops of the British tetanus did not become available until Tetanus has always been a Expeditionary Force between 1939– the introduction of intermittent complication of wounds in wartime. 1940 was 0.43 per 1000, and among positive pressure respiration and There is a dramatic painting of a Allied soldiers in Northwest Europe paralysis in the middle of the wounded soldier with tetanus among between 1944–1945, 0.06 per 1000. twentieth century.

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Bacteriology Intravenous drug addicts who Clinical features of tetanus Tetanus is caused by a produced ‘dilute’ heroin by mixing it with quinine It is difficult to give an incubation by Clostridium tetani (Figure 1), a are at risk from tetanus, as this causes period for tetanus, as spores may motile Gram-positive strictly anaerobic tissue necrosis, thereby providing an remain dormant in tissues for weeks bacillus that produces subterminal ideal environment for the to years, until conditions are suitable spores, although not every strain is of spores and the growth of the for exosporulation to take place. In a sporogenic. The organism grows vegetative organism. Elderly patients deep wound contaminated with soil, under strictly anaerobic conditions on are also at risk due to the decline in the incubation period will be a matter laboratory media. levels following immunisation of days. The incubation period for Though vegetative forms of C. in their youth. tetanus neonatorum, or neonatal tetani are easily killed by heat, the tetanus, is usually less than a week. spores are more resistant. Some are Pathogenesis The characteristic clinical signs of killed by boiling for 15 minutes, All the symptoms of tetanus arise tetanus are spasm and rigidity of the whereas others may survive for up to from a toxin produced by the voluntary muscles, in particular the three hours. Most spores are killed vegetative organism: they do not arise masseters, the abdominal muscles within a few hours by a 1% aqueous from invasion of tissues by C. tetani. and the erector spinae. Muscular solution of iodine, or by a 10-volume Spores of C. tetani have been isolated rigidity persists throughout the illness, solution of hydrogen peroxide. The from soil, street dust and, in the past, and can be detected by palpation. difficulty in killing spores explains why the dust in operating theatres. They Spasms are intermittent. They may cases of postoperative tetanus have enter the body through a wound, only involve the muscles of the mouth been caused by inadequately sterilised which can be as minor as the prick and face, giving rise to risus catgut – spores can survive for years from a thorn. In some cases, the sardonicus (rictus grin), but can also be under the right environmental patient may not remember the injury, generalised. Localised tetanus can conditions. Spores of tetanus have hence the difficulty in estimating the occur in which the rigidity and spasm been isolated in soils throughout the incubation period of the disease. are confined to muscles near an world, and can survive dry heat at 100 Spores will start to germinate if the infected wound. This is usually seen degrees Celsius for one hour. conditions in the tissue are under wartime conditions in soldiers A case of tetanus has been appropriate, the most important of who are partially immune. reported in which spores of C. tetani these being a low oxygen tension. This In some patients the signs of were isolated from abdominal scar is the case in deep, necrotic wounds; tetanus do not progress beyond tissue in a woman who had had an hence the frequency with which trismus (lockjaw), but in others abdominal hysterectomy 10 years tetanus occurs in wounded soldiers. generalised convulsions occur in before developing tetanus. C. tetani produces the toxin which the muscles of the trunk and tetanospasmin, a protein responsible limbs go into violent spasm. The neck Epidemiology for the clinical features of tetanus. It may become extended so that the It is estimated that each year at least is only slightly less toxic than botulin, shoulders are lifted off the bed. This is 100 000 cases of tetanus occur one of the most poisonous chemicals shown in the painting by Sir Charles globally. This is probably an known. The toxin enters peripheral Bell referred to previously. underestimate, as the majority of nerves from adjacent muscle. The frequency of convulsions vary, cases occur in countries with poor Evidence supports the theory that it and may be continuous in severe medical facilities, in which cases are reaches the central cases. The patient remains mentally likely to go unreported. About 60% of by transport in the axons of motor alert and there are no signs of cases occur in neonates and children nerves. It is probable that it is also generalised toxaemia. Difficulty in under five years old. disseminated to distant sites via passing urine, together with Between January and December lymphatic vessels and the constipation, is common. 2013, seven cases of tetanus were bloodstream. After entering pre- Cephalic tetanus can follow reported in England and Wales. The synaptic nerves, it binds to neuronal wounds of the head and neck. patients were aged between 35–82. gangliosides, inhibiting the release of Dysphagia is usually a prominent Two were intravenous drug addicts, . Its main action is symptom; diagnosis can be difficult as three cases sustained lacerations in to inhibit the action of interneurons, generalised convulsions may the home or garden, and one was responsible for the inhibition of be absent. injured on a farm. The seventh patient motor neurones, with the result that There are few complications in had no recorded injury. None of the the patient develops muscular rigidity cases of mild or moderately severe patients died. and spasm. tetanus that are only managed by

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sedation. The main danger arises Box 1. Tetanus-prone wounds as defined by Public Health England from aspiration of secretions, which can occur during or after a spasm. This can lead to collapse of part of a ● Wounds or burns that need surgery, but where surgery cannot be lung, or to pneumonia. The latter is performed within 24 hours the most common cause of death in ● Wounds or burns where a significant amount of tissue has been removed, or tetanus neonatorum. puncture-type injuries such as animal bites, particularly if they have had Bone fractures, including contact with soil or manure compression fractures of vertebrae, ● Wounds containing any substance that should not be there, such as dust or can occur as a result of muscular dirt (foreign bodies) spasm. Several complications can ● Serious fractures where the bone is exposed and prone to infection occur in patients with severe tetanus (compound fractures) who are paralysed and on respiratory ● Wounds and burns in people who have systemic sepsis support. Cardiovascular complications, in particular a labile blood pressure, is tetanus. Strychnine poisoning can autonomic nervous system should be probably due to the action of cause spasms similar to those of ‘stabilised’ with sedatives and, if tetanospasmin on the brainstem. This tetanus, but there is complete necessary, drugs to control a labile can be accompanied by severe muscular relaxation between blood pressure. sweating, which may be followed by spasms. The symptoms of rabies can The patient may need to be failure of the peripheral circulation. also be similar, but the spasms tend paralysed and put on a ventilator; Hyperpyrexia, with temperatures to be localised to the muscles of the however, this may not be possible in reaching 40 degrees Celsius (104 neck, mouth and pharynx. Diagnosis some countries with less well degrees Fahrenheit), can be seen in can be difficult if trismus is the main developed medical facilities, in which patients who have been paralysed, symptom, as painful conditions tetanus is common. The author and is a bad prognostic sign. Again, affecting the oropharynx can make looked after a patient in a remote part this is probably due to tetanospasmin it difficult for the patients to open of Africa in which the only active acting on the brainstem. Dilatation of their mouths. treatment available was sedation the stomach and intestines can also with diazepam. occur in severe cases: this is usually Treatment fatal. The metabolic rate is increased Skilled nursing is essential in the Prevention in patients with severe tetanus, treatment of tetanus. Close attention Immunisation with tetanus is resulting in weight loss. This can be should be paid to oral hygiene. The very effective at preventing the difficult to prevent. patient must be kept in a darkened disease. In the UK the first dose is There are no permanent sequelae room in which there is little noise, and given at two months of age, followed in patients who have recovered from it is important to monitor the patient’s by a second and third dose at monthly tetanus. In countries where intensive weight together with fluid balance. intervals. Booster doses are given at care facilities are good, most patients Human anti-tetanus three to five years, and at 13–18. No should recover. However, an attack of immunoglobulin should be given to further doses are given unless a tetanus, however severe, does not neutralise any toxin that is still in the patient has a wound that is likely to confer immunity to further episodes of circulation. There is evidence that give rise to tetanus (Box 1). the illness. intrathecal administration diminishes All wounds should be thoroughly the severity of the illness. Anti-toxin cleaned and debrided if necessary. It Diagnosis will have no effect on toxin that is may be appropriate to give anti-toxin, Diagnosis is based on clinical signs already bound to gangliosides. with or without tetanus immunisation, and symptoms. Laboratory Metronidazole should be given to if the patient has a deep wound investigations are of no value. It may eradicate vegetative stages of C. contaminated with soil. be possible to isolate C. tetani from tetani that may still be in the wound. A booster tetanus injection is material taken from a wound; This antibacterial agent is preferable to recommended for people travelling to however, by the time the organism penicillin as the latter can act as a an area with limited medical facilities has been grown in the laboratory, an competitive inhibitor of gamma-amino whose last tetanus injection was more astute clinician will have already made butyric acid, one of the neuroinhibitors than 10 years ago. the diagnosis. affected by tetanospasmin. There are other conditions that Muscular spasms should be Declaration of interests: none may simulate the clinical features of controlled with diazepam. The declared.

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