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tetanus (tĕtˈnəs, –ənəs) or lockjaw, acute infectious disease of the central nervous system caused by the toxins of Clostridium tetani. The organism has a widespread distribution and is common in the soil, human and animal feces, and the digestive tracts of animals and humans; however, the toxin is destroyed by intestinal enzymes. Infection with the tetanus bacillus may follow any type of injury, whether incurred indoors or out, including nail puncture wounds, insect bites, splinter injuries, gunshot wounds, burns, lacerations, and fractures. Deep puncture wounds are most dangerous, since the bacillus thrives in an anaerobic environment.
The tetanus toxin, one of the most potent poisons known, acts on the motor nerves and causes muscle spasm at the site of infection and in other areas of the body. The most frequent symptom is stiffness of the jaw (lockjaw) and facial muscles. Difficulty in breathing and severe convulsions may ensue. The mortality rate is very high, especially in the very young and the aged; overall it is about 40%. Treatment with tetanus antitoxin should be started promptly in conjunction with human immune globulin. It is preferable, however, to prevent the disease by active immunization (including booster shots) with tetanus toxoid (see vaccination).
an acute infectious disease of humans and animals characterized by severe spasms resulting from an injury to the central nervous system. The causative agent of tetanus is the tetanus bacillus—Clostridium tetani—an anaerobe whose spores are highly resistant, being able to withstand boiling for as long as half an hour and surviving for years in the soil and on various objects. The soil is contaminated by the feces of animals (usually ruminants) and sometimes of humans (whom the bacilli parasitize but do not disease).
Tetanus is caused by the deposition of the spores of the causative agent into a wound in which necrotic tissue is present (anaerobic conditions). Deposition may occur with soil or a piece of fabric or wood harboring the spores. The disease is common among troops during wartime. It may also be caused by minor injuries that occur in the home, for example, while walking barefoot, as well as by injuries that occur in farm areas. It rarely affects industrial workers. Less frequently, tetanus is caused by burns, frostbite, animal bites, and parturition and abortion performed under unsanitary conditions. In the USSR, rare cases of the disease are recorded.
The incubation period of tetanus is from three to 30 days; the shorter the period, the more severe the course of the disease will be. The prodromal period is accompanied by severe pain in the wound. Primary tetanic manifestations include clonic and tonic spasms of the skeletal muscles, the twitching of the muscles adjacent to the wound, a sensation of general muscular constraint, and pain in the throat upon swallowing. Also characteristic of the disease are trismus (a difficulty in opening the mouth resulting from spasms of the masseter muscles) and risus sardonicus (a grotesque grinning expression caused by the spasmodic contraction of the facial muscles). Tonic spasms gradually spread to the muscles of the neck, torso, and abdomen. The head is thrown back, and the spinal cord is arched forward. An individual suffering from tetanus touches the bed only with the occiput and heels.
The spasms may develop spontaneously or as a response to external stimuli, for example, any noise or light. They may last from several seconds to several minutes, sometimes becoming so severe that they may cause the rupture of muscles and fracture of bones. Spasms of the respiratory muscles, diaphragm, or fissure of the glottis may lead to sudden death by asphyxia. Throughout the disease consciousness is maintained. The body temperature is normal or slightly increased. In addition to the common form of tetanus, there are also fulminating, recurrent, and other forms.
The treatment of tetanus includes supportive nursing care. The diseased individual should be kept in an environment conducive to relaxation and should be under the constant care of a physician. A well-balanced diet is important, as is antispasmodic therapy. In severe cases, curare-like drugs are used and artificial lung ventilation is administered. Large doses of antitoxin (gamma globulin) are injected to neutralize the tetanus toxin, and measures are taken to prevent and treat pulmonary complications. Therapeutic measures may be carried out most effectively in reanimation units, to which the individual is transported in the company of a physician.
The preventive treatment of tetanus includes a planned system of immunization and prompt treatment in cases of injuries. In the USSR, children are immunized using a triple vaccine (whooping cough-diphtheria-tetanus), and adults (most important, those living in rural areas in the southwest and southeast, construction workers, and sanitation workers) are immunized using adsorbed tetanus toxoid. In cases of injuries, active-passive prophylaxis (toxoid and antitoxin preparations) is used; if the individual was previously vaccinated, only toxoids are used.
REFERENCESRukovodstvo po infektsionnym bolezniam. Edited by A. F. Bilibin and G. P. Rudnev. Moscow, 1962.
Obshchaia i chastnaia epidemiologiia, vol. 2. Edited by I. I. Elkin. Moscow, 1973.
V. L. VASILEVSKII and A. G. KISSIN
In animals. Horses, cattle, swine, dogs, cats, and birds may become afflicted with tetanus, with young animals being more susceptible. Infection occurs when the spores of the tetanus microbe are introduced into a wound along with dirt or manure. The incubation period is one to three weeks.
Tetanus is manifested by the spasmodic contraction of the musculature of the body, primarily of the masseter muscles (trismus). There is frequently a prolapse of the third eyelid, and the nostrils become infundibular in form. Retraction of the abdominal wall develops along the costal margin, and locomotion becomes difficult. The animal assumes a sawbuck stance, with neck and tail extended. In large animals the entire musculature of the body is affected, whereas in swine and dogs frequently only the masseter muscles contract. The body temperature is normal until immediately before death, when it rises to 40°–42°C.
Tetanus is treated with antitoxins, chloral hydrate, and amina-zine. Preventive treatment includes the immediate cleansing of the wound, the observance of aseptic and antiseptic conditions during castration or parturition, and the immunization of livestock with alum precipitated toxoid.
REFERENCEEpizootologiia, 2nd ed. Edited by R. F. Sosov. Moscow, 1974. Pages 89–94.
R. F. SOSOV
in physiology, the prolonged contraction of a muscle caused by a steady succession of nerve impulses at short intervals—a contraction based on the temporal summation of successive individual contraction waves. A tetanus occurs when the rate of muscle stimulation is so high that a new contraction begins before the preceding one has ended. This is called tetanic contraction, with the contraction waves seemingly superimposed on each other; the result is that the muscle remains contracted throughout the period of stimulation.
Two types of tetanus may be distinguished. In saw-tooth tetanus, a muscle begins to contract in response to each of a series of stimuli succeeding each other with no interval of complete relaxation. In even tetanus, with a higher rate of stimulation, the muscle receives each succeeding stimulus during the phase of muscle contraction.
Tetanic contractions are accompanied by a process that confirms their cumulative nature—namely, the rhythmical development of electrical action potentials in a muscle with each onset of excitation. A tetanic contraction greatly exceeds a single contraction in amplitude and duration. The various forms of a tetanus are determined by the particular phase, or degree of excitability, of the muscle when stimulated. The first to relate the intensity of contraction to the level of muscle excitability was N. E. Vvedenskii, who observed that, as the rate of stimulation is increased, the contraction initially reaches its maximum amplitude, or optimum, followed by a sharp drop, or pessimum.
Comparatively rapid fatigability is characteristic of tetanically contracting muscle fibers, inasmuch as the process entails a substantial expenditure of the muscles’ energy supply. It has been demonstrated by electrophysiological methods that the frequency with which nerve impulses travel along the spinal cord’s motoneurons toward the skeletal muscles is several times lower than the frequency of the impulses that cause a tetanus. The smoothness of movement typical of man and of animals, once ascribed to even tetanus, is now thought to be due to the motoneurons’ finely coordinated action, which ensures the alternating phasic contractions of a muscle’s individual fibers.
REFERENCESVvedenskii, N. E. “O sootnosheniiakh mezhdu razdrazheniem i vozbuzhdeniem pri tetanuse.” Poln. sobr. soch., vol. 2. Leningrad, 1951.
Fiziologiia myshechnoi deiatel’nosti, truda i sporta. Leningrad, 1969. (Manual of physiology.)
V. G. ZILOV