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 develop in the jaw (thus the name "lockjaw") and elsewhere in the body.
[1] Infection can be prevented by proper immunization and by
post-exposure prophylaxis.
[2]
[edit] Signs and symptoms
Facial spasms called
Risus Sardonicus-First Symptom of Generalized Tetanus.
Lock-jaw and
risus sardonicus in a patient suffering from tetanus.
An infant suffering from neonatal tetanus.
Tetanus affects
skeletal muscle, a type of
striated muscle used in voluntary movement. The other type of striated muscle, cardiac or
heart muscle, cannot be
tetanized because of its intrinsic electrical properties. Mortality rates reported vary from 48% to 73%. In recent years, approximately 11% of reported tetanus cases have been
fatal. The highest
mortality rates are in unvaccinated people and people over 60 years of age.
[2]
The incubation period of tetanus may be up to several months but is usually about 8 days.
[3][4] In general, the further the injury site is from the
central nervous system, the longer the incubation period. The shorter the incubation period, the more severe the symptoms.
[5] 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.
[2]
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 up to 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.
[6]
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.
[edit] Cause
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 harbor 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 survive well 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 is provided by the same object which causes a puncture
wound, delivering endospores to a suitable environment for growth.
[edit] Pathophysiology
Tetanus begins when
spores of
Clostridium tetani enter damaged tissue. The spores transform into rod-shaped bacteria and produce the neurotoxin
tetanospasmin (also known as tetanus toxin). This toxin is inactive inside the bacteria, but when the bacteria dies, it is released and activated by
proteases. Active tetanospasmin is carried by retrograde
axonal transport[5][7] to the
spinal cord and
brain stem where it binds irreversibly to receptors at these sites.
[5] It cleaves membrane proteins involved in
neuroexocytosis,
[8] which in turn blocks
neurotransmission. Ultimately, this produces the symptoms of the disease. Damaged
upper motor neurons can no longer inhibit lower
motor neurons (see
Renshaw cells), plus they cannot control
reflex responses to afferent sensory stimuli.
[5] Both mechanisms produce the hallmark
muscle rigidity and
spasms. Similarly, a lack of neural control of the
adrenal glands results in release of
catecholamines, thus producing a
hypersympathetic state and widespread
autonomic instability.
C. tetani also produces
tetanolysin, another toxin whose role in tetanus is unknown.
[edit] Diagnosis
There are no blood tests that can be used to diagnose tetanus. The diagnosis is based on the presentation of tetanus symptoms and does not depend upon isolation of the bacteria, which is recovered from the wound in only 30% of cases and can be isolated from patients who do not have tetanus. Laboratory identification of
C. tetani can only be demonstrated by production of tetanospasmin in mice.
[2]
The "spatula test" is a clinical test for tetanus that 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).
[9]
[edit] Prevention
Unlike many infectious diseases, recovery from naturally acquired tetanus does not usually result in
immunity to tetanus. This is due to the extreme potency of the tetanospasmin toxin; even a lethal dose of tetanospasmin is insufficient to provoke an immune response.
Tetanus can be prevented by
vaccination with tetanus toxoid.
[10] 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 may not 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.
[11] 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.
[10]
[edit] Treatment
The wound must be cleaned. Dead and infected tissue should be removed by surgical
debridement. Administration of the antibiotic
metronidazole 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 immunoglobulin 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.
[edit] Mild tetanus
Mild cases of tetanus can be treated with:
[edit] Severe tetanus
Severe cases will require admission to
intensive care. In addition to the measures listed above for mild tetanus:
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 150 g of protein per day, is often given in liquid form through a tube directly into the stomach (
Percutaneous endoscopic gastrostomy), or through a drip into a vein (
Total parenteral nutrition). This high-caloric diet maintenance is required because of the increased metabolic strain brought on by the increased muscle activity. Full recovery takes 4 to 6 weeks because the body must regenerate destroyed nerve
axon terminals.
[edit] Epidemiology
Disability-adjusted life year for tetanus per 100,000 inhabitants in 2004. no data ≤10 10-25 25-50 50-75 75-100 100-125 125-150 150-200 200-250 250-500 500-750 ≥750
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 an international health problem, as
C. 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. This is particularly true with
manure-treated soils, as the spores are widely distributed in the intestines and feces of many non-human animals such as horses, sheep, cattle, dogs, cats, rats, guinea pigs, and chickens. Spores can be introduced into the body through puncture wounds. In agricultural areas, a significant number of human adults may harbor the organism. The spores can also be found on skin surfaces and in contaminated
heroin.
[2] Heroin users, particularly those that inject the drug, appear to be at high risk for tetanus.
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.
[2]
In the United States, approximately 100 people become infected with tetanus each year, and there are about five deaths from tetanus each year.
[12] Nearly all of the cases in the United States occur in unimmunized individuals or individuals who have allowed their
inoculations to lapse,
[12] 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.
[2][12]
[edit] History
Tetanus was well known to ancient people who recognized the relationship between wounds and fatal muscle spasms. The word "tetanus" is derived from the
Greek τέτανος
tetanos meaning "taut", and τείνειν
teinein to "stretch".
[13] In 1884,
Arthur Nicolaier isolated the
strychnine-like toxin of tetanus from free-living, anaerobic soil bacteria. The etiology of the disease was further elucidated in 1884 by
Antonio Carle and
Giorgio Rattone, who demonstrated the transmissibility of tetanus for the first time. They produced tetanus in rabbits by injecting pus from a patient with fatal tetanus into their sciatic nerves. In 1889,
C. tetani was isolated from a human victim by
Kitasato Shibasaburo, who later showed that the organism could produce disease when injected into animals, and that the toxin could be neutralized by specific
antibodies. In 1897,
Edmond Nocard showed that tetanus antitoxin induced
passive immunity in humans, and could be used for
prophylaxis and treatment. Tetanus toxoid
vaccine was developed by P. Descombey in 1924, and was widely used to prevent tetanus induced by battle wounds during
World War II.
[2]
Source:
Tetanus - Wikipedia, the free encyclopedia