The effects of tetanus come from a bacterial neurotoxin released in wounds during infection. This substance blocks the ability of skeletal muscles to relax, and instead makes them contract and spasm. Lockjaw or similar muscular rigidity is a common symptom. The effects of tetanus can be prevented through vaccination, and are often successfully reversed in hospital settings that include respiratory support. In the developing world, tetanus is a significant cause of death in newborn infants.
Clostridium tetani is a bacterium found in soil around the world, contaminating wounds in humans and other animals. The effects of tetanus are caused by a strong neurotoxin, tetanospasmin, manufactured by the bacteria and released when their cells come apart. When circulating the bloodstream, the toxin gradually is absorbed into the nerves, first peripherally, and then in the spinal cord itself. In as little as a week, tetanospasmin blocks neurotransmitter communication, preventing the neurons that control muscles from receiving commands from the brain. It inhibits muscular relaxation, so the skeletal muscles are constantly having contractions.
Muscular contractions across the body often begin with lockjaw, one of the most prominent effects of tetanus. General muscular rigidity, difficulty in swallowing, and paralysis follow. The patient is racked by powerful recurring spasms that can tear muscle and ligament, and even fracture the vertebral column. If it reaches the neurons in the brain stem, tetanus toxin threatens basic functions like breathing. The smooth muscles of the heart do not develop tetany and can still relax because tetanospasmin only blocks the neural control of skeletal muscle,.
Since it is rare in vaccinated individuals, tetanus is best prevented by vaccination at regular intervals, at least once a decade for adults. Treatment includes antibiotics, muscle relaxants, and hospitalized care. Since the most common cause of death from the effects of tetanus is respiratory failure, artificial respiration may be necessary for as long as the toxin is suppressing normal breathing. Recovery rates are fairly high outside of the elderly and some unvaccinated patients. Death rates vary widely, from less than a tenth of cases in parts of the developed world to over half in more impoverished countries.
In newborns, the effects of tetanus are similar to those in adults but follow a quicker and often lethal course. Neonatal tetanus is often acquired from cutting of the umbilical cord by a knife or scissors not properly sterilized, though contact with soil can be a factor. It is a common cause of early infant mortality in the developing world, though rare elsewhere. If an infant's mother has been vaccinated, neonatal odds of acquiring tetanus drop, regardless of sanitation, since passive immunity can be acquired by a fetus during the course of pregnancy.