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.The tetanus toxin initially binds to peripheral nerve terminals. It is transported within the axon and across synaptic junctions until it reaches the central nervous system. There it becomes rapidly fixed to gangliosides at the presynaptic inhibitory motor nerve endings, and is taken up into the axon by endocytosis. The effect of the toxin is to block the release of inhibitory neurotransmitters glycine and gamma-aminobutyric acid (GABA) across the synaptic cleft, which is required to check the nervous impulse.
If nervous impulses cannot be checked by normal inhibitory mechanisms, the generalized muscular spasms characteristic of tetanus are produced. The toxin appears to act by selective cleavage of a protein component of synaptic vesicles, synaptobrevin II, and this prevents the release of neurotransmitters by the cells Passive immunization with human tetanus immune globulin (TIG) shortens the course of tetanus and may lessen its severity. A dose of 500 U may be as effective as larger doses. Therapeutic TIG (3,000-6,000 units as 1 dose) has also been recommended for generalized tetanus.Other treatment measures include ventilatory support, high-calorie nutritional support, and pharmacologic agents that treat reflex muscle spasms, rigidity, tetanic seizures and infections.
In Finland, during the period 1969-1985, 28 (26%) of the 106 cases of tetanus were caused by occupational accidents, 16 of which occurred in agriculture and forestry. Twenty-one of the patients were men and seven were women. The mean annual incidence of tetanus was 1 per 100,000 occupational accidents during the study period. The cases were concentrated in summer and autumn. Most of the primary injuries were minor, 61% of the injuries occurring in the hands and fingers. Forty-three percent of the patients had not been immunized against tetanus, and 46% were unaware of their state of immunization. The systematic immunization of the population against tetanus is important because the disease is often caused by slight injuries not requiring treatment by health care personnel. This need is emphasized for work in agriculture, forestry, and other branches in which contact with soil or animals occurs.