Tetanus

Related Topics:
Tetanus_Toxoid :: Tetanus

Tetanus is a serious and often fatal disease caused by the neurotoxin tetanospasmin which is produced by the Gram-positive, obligate anaerobic bacterium Clostridium tetani. Infection usually originates from a contaminated wound, often a cut or deep puncture wound. Common symptoms are muscle spasms in the jaw (hence the common name lockjaw), followed by difficulty swallowing and general muscle stiffness in other parts of the body. Infection can be prevented by proper immunization, as well as by post-exposure prophylaxis.

Tetany refers to a state of muscle tension.

General information

Tetanus was first documented by Hippocrates, and records dating back to the 5th century BC document countless distinctive clinical observations of the disease. However, the etiology of the disease was not discovered until 1884 by Berlin physician Arthur Nicolaier. Shibasaburo Kitasato and Emil von Behring obtained a pure culture in 1899. Passive tetanus immunization was first implemented during World War I.

Bacilli of C. tetani can be found in soil (especially agricultural soil), and the intestines and feces of horses, sheep, cattle, rats, dogs, cats, guinea pigs, and chickens. Spores are found in manure-treated soil, skin surfaces (of both animals and humans), under nail-beds, and in contaminated heroin.

There are four different clinical forms of tetanus: local (uncommon), cephalic (rare), generalized (most common), and neonatal (a common cause of infant mortality in underdeveloped countries). Generalized tetanus accounts for 80% of tetanus cases.

Symptoms

The incubation period for tetanus is 3 days to as long as 15 weeks (with the average being about 8 days) ^*. For neonates, the incubation period is 4 to 14 days, with 7 days being the average. Most of the time, the further the wound is from the central nervous system, the longer the incubation period. Incubation period length and likelihood of death are inversely proportional; a deep, contaminated wound that allows the bacteria to flourish and causes a quick, aggressive infection is much more life-threatening than a shallower, less-contaminated wound that causes milder symptoms to appear days or weeks later.

The first sign of tetanus is a mild jaw muscle spasm called lockjaw (trismus), followed by stiffness of the neck and back, risus sardonicus, difficulty swallowing, and muscle rigidity in the abdomen. The stiffness and spasming of muscles expands throughout the body inferiorly, and can be so powerful that they cause muscle tears and even fractures^*. These muscle contractions are due to tetanospasmin—a chemical released by C. tetani—which inhibits the release of both GABA and glycine, the neurotransmitters that serve to inhibit muscle contraction.

Typical signs of tetanus include an increase in body temperature by 2 to 4°C, diaphoresis (excessive sweating), an elevated blood pressure, and an episodic rapid heart rate. Spasms and muscle contraction last for 3 to 4 weeks, and complete recovery may take months. About 30% of tetanus victims die, most of whom are elderly patients. In developing countries, the mortality rate may be as high as 60%.

Complications of the disease include spasms of the larynx (vocal cords), accessory muscles (chest muscles used to aid in breathing), and the diaphragm (the primary breathing muscle); fractures of long bones secondary to violent muscle spasms; and hyperactivity of the autonomic nervous system.

Treatment

The wound must be cleaned; dead and infected tissue should be removed by surgical debridement. Metronidazole will help decrease the amount of bacteria but has no effect on the bacterial toxin. Penicillin has been used in the past to treat tetanus, but is no longer the treatment of choice because there is a theoretical risk that it can increase spasms; however, if metronidazole is not available penicillin should still be used. Human anti-tetanospasmin immunoglobulin (or tetanus immune globulin) is a crucial part of treatment; if specific anti-tetanospasmin immunoglobulin is not available then human normal immunoglobulin may be given instead. All tetanus victims should be vaccinated against tetanus or offered a booster vaccine if they have been previously vaccinated.

Mild tetanus

Mild cases of tetanus can be treated on the ward. In addition to the measures given above:

5000 units tetanus immune globulin IV or IM
metronidazole 500mg IV for 10 days
diazepam 5 to 20mg tds PO
tetanus vaccination

Severe tetanus

These patients will require admission to intensive care. In additional to the measures listed above for mild tetanus:

human tetanus immunoglobulin 1000 units intrathecally (increases clinical improvement from 4% to 35%)
tracheostomy and mechanical ventilation for 3 to 4 weeks
diazepam 20 to 100mg per day continuous IV infusion
autonomic features can be difficult to manage (alternating hyper- and hypotension, hyperpyrexia/hypothermia) and may require IV labetalol, magnesium, clonidine, nifedipine, etc.

Prevention

Tetanus can be prevented by vaccination. A booster vaccine is recommended every ten years, and standard care in many places is to give the booster to any patient with a puncture wound who is uncertain of when he or she was last vaccinated. One Tetanus booster used presently is called TDap or DTaP (a protection from Diphtheria and Pertussis as well). The risk from Tetanus, Diphtheria and Pertussis (whooping cough) is higher than the risk of vaccine side-effects. There was a shortage of tetanus vaccine in the United States in 2001 and 2002, but this supply issue was corrected in 2003.

Worldwide, there are approximately one million cases of tetanus each year. (There are about 100 cases and approximately five deaths each year in the USA.) ^*

Association with rust

Tetanus is often associated with rust, especially rusty nails, but this is somewhat misleading. Rust itself does not cause tetanus or contain more C. tetani bacteria. Objects that accumulate rust are often found in the outdoors or places that generally contain more bacteria. Since C. tetani is an anaerobic bacterium, it will thrive in an environment that lacks oxygen. Therefore, stepping on an old forgotten nail in a stable could easily result in tetanus, partly because C. tetani is found in animal feces (which is rather abundant in a stable) and the puncture wound would effectively create an ideal breeding ground for the bacteria (because of the lack of oxygen). Such an old nail would likely be rusty, but a lack of rust would provide no protection. On the other hand, someone scratching themselves against a rusty fire escape ladder in an urban setting would have a much lesser chance of getting tetanus since fire escape ladders do not often come into intimate contact with soil, dirt or organic waste and the wound itself (eg a scratch) does not create an oxygen-poor environment.

Around the globe

Tetanus is a global health problem since Clostridium tetani spores are ubiquitous. The disease occurs almost exclusively in persons who are unvaccinated or inadequately immunized. Tetanus occurs worldwide but is more common in hot, damp climates with soil rich in organic matter. Tetanus, particularly the neonatal form, remains a significant public health problem in non-industrialized countries, causing an estimated 300,000 to 500,000 deaths each year.

External links

Infectious diseases | Bacterial diseases

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