Tetanus
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Tetanus is a medical term indicating a prolonged contraction of skeletal muscle fibers. Skeletal muscle is a type of striated muscle. The other type of striated muscle, cardiac or heart muscle cannot be tetanized due to intrinsic electrical properties. If the condition is caused by exposure to certain bacteria, a serious and often fatal disease may result. Tetanus is the primary symptom 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.[1]
Infection can be prevented by proper immunization, as well as by post-exposure prophylaxis.
Tetany refers to a state of muscle tension.
Symptoms
The incubation period for tetanus is 3 days to as long as 15 weeks, with the average being about 8 days.[2] 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 bone fractures.[3] 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%.In treated cases, the rate of death is less than 10%.
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. Blockage of the airways is a common effect.
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. In the most severe of cases, it may be necessary to paralyze the patient using a naturally occurring substance, and engage a machine to continue breathing.
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 addition to the measures listed above for mild tetanus:
- human tetanus immunoglobulin 1000 units injected intrathecally (increases clinical improvement from 4% to 35%)
- tracheostomy and mechanical ventilation for 3 to 4 weeks
- magnesium, as an intravenous infusion, to prevent muscle spasm
- 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.[4] A booster vaccine is recommended every six 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. This booster cannot prevent a potentially fatal case of tetanus from the current wound as it takes 2 weeks for antibodies to form. For children under the age of seven, the tetanus vaccine is often administered as a combined vaccine, TDap or DTaP, which include vaccines against diphtheria and pertussis as well). For adults and children over seven, the Td vaccine (tetanus and diptheria) is commonly used.[4]
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 anaerobic bacteria. Since C. tetani is an anaerobic bacterium, it will thrive in an environment that lacks oxygen. The rough surface of rusty metal provides a prime habitat for the endospore to reside. This endospore is a non-metabolising survival structure and once in an adequate environment (e.g. a puncture wound) it begins metabolising and an infection begins. 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 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 (e.g. a scratch) does not create an oxygen-poor environment.
Epidemiology
Tetanus is a global health problem since C. tetani and Geravium tetani spores are ubiquitous. The disease occurs almost exclusively in persons who are unvaccinated or inadequately immunized.[1] 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.
In the US, there are about 100 cases and approximately five deaths each year.[5]
References
- ^ a b Wells CL, Wilkins TD (1996). Clostridia: Sporeforming Anaerobic Bacilli. In: Baron's Medical Microbiology (Baron S et al, eds.) (4th ed. ed.). Univ of Texas Medical Branch. (via NCBI Bookshelf) ISBN 0-9631172-1-1.
{{cite book}}:|edition=has extra text (help) - ^ "Tetanus". MedlinePlus. Retrieved 2006-09-20.
- ^ "Chapter 157. Bacterial Diseases". The Merck Manual of Diagnosis and Therapy. Retrieved 2006-09-20.
- ^ a b "Diphtheria, tetanus, and pertussis: recommendations for vaccine use and other preventive measures. Recommendations of the Immunization Practices Advisory committee (ACIP)". MMWR Recomm Rep. 40 (RR-10): 1–28. 1991. PMID 1865873.
- ^ "Tetanus Cases Prompt Advisory for Missourians to Get Vaccine, Check Booster Status". NewsAndPublicNotices. Retrieved 2006-09-20.