I.Before reading the text look through the list of the following medical terms, be sure you know their meaning:
neurotoxin [
tetanospasmin
obligate
trismus,
risus sardonicus
opisthotonos
tetany
|
|
Tetanus Classification and external resources |
|
Tetanus is an acute, often-fatal medical condition that is characterized by a prolonged contraction of skeletal muscle fibres. 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 a puncture wound. Deep wounds or those with devitalized tissue are particularly prone to tetanus infection. As the infection progresses, muscle spasms in the jaw develop, hence the common 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.
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. Worldwide, as many as 50, 000 people die each year from tetanus. 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 is. 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 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. Spasm of the facial muscles produces a facial expression of a fixed smile and raised eyebrows called risus sardonicus. The first and the most common sign is stiffness of the jaw or trismus, which accounts for the name “lockjaw” 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 newborn infants. It occurs in infants who have not acquired passive immunity because the mother has never been immunized. 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.
Tetanus vaccine is a toxoid, meaning that it protects against the toxin produced by bacteria. Tetanus immunization is almost always administered to children in the form of the DTaP vaccine, which also protects against diphtheria and pertusis. Tetanus toxoid can also be given in combination with diphtheria vaccine alone in both adult (Td) and pediatric (DT) formulations. Infants are commonly given the DTaP vaccine in a schedule of four doses at 2, 4, 6, and 15-18 months of age. Another dose is administered at 4 to 6 years of age. Since the levels of antixon in the body gradually fall over time, booster vaccinations with the combined diphtheria-tetanus toxoid (Td) are recommended every 10 years. If it has been more than 10 years since a person has had last tetanus booster, it is imperative to contact a doctor to bring immunization up to date. A booster vaccination is also recommended if a patient has sustained a deep contaminated wound and more than five years have passed since the last dose because protective antibody levels may fall after five years in some people. An individual should also receive a series of three tetanus immunizations provided he or she did not get the childhood vaccine.
Serious adverse reactions from the tetanus shot are very rare. Mild reactions include localized swelling, tenderness, and redness at the injection site that generally persist for one to two days after vaccination.