Tetanus

Alternative names:

lockjaw

Definition:

A disease caused by the toxin of the bacterium Clostridium tetani that affects the central nervous system, sometimes resulting in death.

Causes, incidence, and risk factors:

Spores of the bacterium Clostridium tetani live in the soil and are distributed worldwide. In the spore form, Clostridium tetani may remain dormant in the soil but infectious for periods longer than 40 years. Infection begins when the spores are introduced into an injury or wound. The spores germinate, releasing active bacteria that multiply, and produce a neurotoxin, called tetanospasmin. Tetanospasmin selectively blocks inhibitory nerve transmission from the spinal cord to the muscles, allowing the muscles to go into severe spasm. Spasmodic contractions may be so powerful that they tear the muscles or cause compression fractures of the vertebrae.

Tetanus often begins with mild spasms in the jaw muscles (trismus), neck muscles, and facial muscles. Rigidity rapidly develops in the chest, back and abdominal muscles and sometimes the laryngeal muscles (which then interferes with breathing). Muscular seizures (tetany) cause sudden, powerful, and painful contraction of muscle groups. During these episodes, fractures and muscle tears can occur. Without treatment, 1 out of 3 affected people die. The mortality rate for newborns with untreated tetanus is even higher, 2 out of 3.

The incubation period is 5 days to 15 weeks, with 8 to 12 days as the average. About 100 cases of tetanus occur every year in the U.S., all in unimmunized individuals or those whose last immunization was no longer current. In developing countries, tetanus frequently causes death in newborn infants when the umbilical stump becomes infected.