Tetanus

Tetanus

Tetanus, also called lockjaw, is a medical condition characterized by a prolonged contraction of skeletal muscle fibers. The primary symptoms are caused by tetanospasmin, a neurotoxin produced by the Gram-positive, obligate anaerobic bacterium Clostridium tetani. Infection generally occurs through wound contamination, and often involves a cut or deep puncture wound. As the infection progresses, muscle spasms in the jaw develop, hence the name lockjaw. This is followed by difficulty in swallowing and general muscle stiffness and spasms in other parts of the body. Infection can be prevented by proper immunization and by post-exposure prophylaxis.

Signs and symptoms

Tetanus affects skeletal muscle, a type of striated muscle. The other type of striated muscle, cardiac or heart muscle, cannot be tetanized because of its intrinsic electrical properties. In recent years, approximately 11% of reported tetanus cases have been fatal. The highest mortality rates are in unvaccinated persons and persons over 60 years of age. C. tetani, the bacterium that causes tetanus, is recovered from the initial wound in only about 30% of cases, and can be found in patients who do not have tetanus.

The incubation period of tetanus ranges from 3 to 21 days, with an average onset of clinical presentation of symptoms in 8 days. In general, the further the injury site is from the central nervous system, the longer the incubation period. The shorter the incubation period, the higher the chance of death. In neonatal tetanus, symptoms usually appear from 4 to 14 days after birth, averaging about 7 days. On the basis of clinical findings, four different forms of tetanus have been described.

Local tetanus is an uncommon form of the disease, in which patients have persistent contraction of muscles in the same anatomic area as the injury. The contractions may persist for many weeks before gradually subsiding. Local tetanus is generally milder; only about 1% of cases are fatal, but it may precede the onset of generalized tetanus.

Cephalic tetanus is a rare form of the disease, occasionally occurring with otitis media (ear infections) in which C. tetani is present in the flora of the middle ear, or following injuries to the head. There is involvement of the cranial nerves, especially in the facial area.

Generalized tetanus is the most common type of tetanus, representing about 80% of cases. The generalized form usually presents with a descending pattern. The first sign is trismus, or lockjaw, and the facial spasms called risus sardonicus, followed by stiffness of the neck, difficulty in swallowing, and rigidity of pectoral and calf muscles. Other symptoms include elevated temperature, sweating, elevated blood pressure, and episodic rapid heart rate. Spasms may occur frequently and last for several minutes with the body shaped into a characteristic form called opisthotonos. Spasms continue for 3–4 weeks, and complete recovery may take months.

Neonatal tetanus is a form of generalized tetanus that occurs in newborns. Infants who have not acquired passive immunity because the mother has never been immunized are at risk. It usually occurs through infection of the unhealed umbilical stump, particularly when the stump is cut with a non-sterile instrument. Neonatal tetanus is common in many developing countries and is responsible for about 14% (215,000) of all neonatal deaths, but is very rare in developed countries.

Spatula test

The "spatula test" for tetanus involves touching the posterior pharyngeal wall with a sterile, soft-tipped instrument, and observing the effect. A positive test result is the involuntary contraction of the jaw (biting down on the "spatula"), and a negative test result would normally be a gag reflex attempting to expel the foreign object.

A short report in The American Journal of Tropical Medicine and Hygiene states that in a patient research study, the spatula test had a high specificity (zero false-positive test results) and a high sensitivity (94% of infected patients produced a positive test result).

Treatment

The wound must be cleaned. Dead and infected tissue should be removed by surgical debridement. Metronidazole treatment decreases the number of bacteria but has no effect on the bacterial toxin. Penicillin was once used to treat tetanus, but is no longer the treatment of choice, owing to a theoretical risk of increased spasms. However, its use is recommended if metronidazole is not available. Passive immunization with human anti-tetanospasmin immunoglobulin or tetanus immune globulin is crucial. If specific anti-tetanospasmin immunoglobulin is not available, then normal human immunoglobulin may be given instead. All tetanus victims should be vaccinated against the disease or offered a booster shot.

An infant suffering from neonatal tetanus.

Mild tetanus

Mild cases of tetanus can be treated with:

• Tetanus immune globulin IV or IM
• metronidazole IV for 10 days
• diazepam
• tetanus vaccination

Severe tetanus

Severe cases will require admission to intensive care. In addition to the measures listed above for mild tetanus:

Lock-jaw in a patient suffering from tetanus.

• human tetanus immunoglobulin injected intrathecally (increases clinical improvement from 4% to 35%)
• tracheostomy and mechanical ventilation for 3 to 4 weeks,
• magnesium, as an intravenous (IV) infusion, to prevent muscle spasm,
• diazepam (known under the common name Valium) as a continuous IV infusion,
• the autonomic effects of tetanus can be difficult to manage (alternating hyper- and hypotension, hyperpyrexia/hypothermia) and may require IV labetalol, magnesium, clonidine, or nifedipine.

Drugs such as diazepam or other muscle relaxants can be given to control the muscle spasms. In extreme cases it may be necessary to paralyze the patient with curare-like drugs and use a mechanical ventilator.

In order to survive a tetanus infection, the maintenance of an airway and proper nutrition are required. An intake of 3500-4000 Calories, and at least 150g of protein per day, is often given in liquid form through a tube directly into the stomach, or through a drip into a vein. This high-caloric diet maintenance is required because of the increased metabolic strain brought on by the increased muscle activity.

Prevention

Tetanus can be prevented by vaccination. The CDC recommends that adults receive a booster vaccine every ten years, and standard care practice 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, or if he or she has had fewer than 3 lifetime doses of the vaccine. The booster cannot prevent a potentially fatal case of tetanus from the current wound, however, as it can take up to two weeks for tetanus antibodies to form. In children under the age of seven, the tetanus vaccine is often administered as a combined vaccine, DPT/DTaP vaccine, which also includes vaccines against diphtheria and pertussis. For adults and children over seven, the Td vaccine (tetanus and diphtheria) or Tdap (tetanus, diphtheria, and acellular pertussis) is commonly used.

Epidemiology

Tetanus cases reported worldwide (1990-2004). Ranging from strongly prevalent (in dark red) to very few cases (in light yellow) (grey, no data).

Tetanus is a global health problem, as C. 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. This is particularly true with manure-treated soils, as the spores are widely distributed in the intestines and faeces of many non-human animals such as horses, sheep, cattle, dogs, cats, rats, guinea pigs, and chickens. In agricultural areas, a significant number of human adults may harbour the organism. The spores can also be found on skin surfaces and in contaminated heroin.

Tetanus – particularly the neonatal form – remains a significant public health problem in non-industrialized countries. There are about one million cases of tetanus reported worldwide annually, causing an estimated 300,000 to 500,000 deaths each year.

In the United States, approximately 100 people become infected with tetanus each year, and there are about five deaths from tetanus each year. Nearly all of the cases in the United States occur in unimmunized individuals or individuals who have allowed their inoculations to lapse, whereas most cases in developing countries are due to the neonatal form of tetanus.

Tetanus is the only vaccine-preventable disease that is infectious but is not contagious.

Association with rust

Tetanus is often associated with rust, especially rusty nails, but this concept is somewhat misleading. Objects that accumulate rust are often found outdoors, or in places that harbour anaerobic bacteria, but the rust itself does not cause tetanus nor does it contain more C. tetani bacteria. The rough surface of rusty metal merely provides a prime habitat for a C. tetani endospore to reside, and the nail affords a means to puncture skin and deliver endospore into the wound. An endospore is a non-metabolising survival structure that begins to metabolise and cause infection once in an adequate environment. Because C. tetani is an anaerobic bacterium, it and its endospores will thrive in an environment that lacks oxygen. Hence, stepping on a nail (rusty or not) may result in a tetanus infection, as the low-oxygen (anaerobic) environment of a puncture wound provides the bacteria with an ideal breeding ground.

Famous tetanus victims

• George Montagu – English ornithologist; contracted tetanus when he stepped on a nail.
• Joe Powell – English footballer; contracted following amputation of a badly broken arm.
• John A. Roebling – Civil Engineer and Architect famous for his bridge designs, particularly the Brooklyn Bridge; contracted tetanus following amputation of his foot due to an injury caused by a ferry when it crashed into a wharf.
• George Crockett Strong – Union brigadier general in the American Civil War; from wounds sustained in the assault against Fort Wagner on Morris Island, South Carolina.
• Fred Thomson – silent film actor; stepped on a nail.
• Johann Tserclaes, Count of Tilly; wounded by a cannon ball in the Battle of Rain.
• Traveller – General Robert E. Lee's favorite horse; stepped on a nail.
• George Hogg – English adventurer who rescued war orphans in China; died in 1945 from an infection resulting from a foot injury.
• Joe Hill Louis – Memphis blues musician; died in 1957 as a result of an infected wound to his thumb.
• Tom Butler – English footballer; contracted after suffering a badly broken arm.

External links

• Tetanus Information from Medline Plus
• Tetanus Surveillance -- United States, 1998-2000 (Data and Analysis)

Media

• Video: Generalized tetanus in a 70-year-old woman (Neurology)
• Video: Tetanus in dogs