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. 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. 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 (ear infections) 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. The first sign is trismus, or lockjaw, and the facial spasms called risus sardonicus, 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.
A short report in The American Journal of Tropical Medicine and Hygiene states that in a patient research study, the spatula test had a high specificity (zero false-positive test results) and a high sensitivity (94% of infected patients produced a positive test result).
The wound must be cleaned. Dead and infected tissue should be removed by surgical debridement. Metronidazole treatment decreases the number of bacteria but has no effect on the bacterial toxin. Penicillin was once used to treat tetanus, but is no longer the treatment of choice, owing to a theoretical risk of increased spasms. However, its use is recommended if metronidazole is not available. Passive immunization with human anti-tetanospasmin immunoglobulin or tetanus immune globulin is crucial. If specific anti-tetanospasmin immunoglobulin is not available, then normal human immunoglobulin may be given instead. All tetanus victims should be vaccinated against the disease or offered a booster shot.
Drugs such as diazepam or other muscle relaxants can be given to control the muscle spasms. In extreme cases it may be necessary to paralyze the patient with curare-like drugs and use a mechanical ventilator.
In order to survive a tetanus infection, the maintenance of an airway and proper nutrition are required. An intake of 3500-4000 Calories, and at least 150g of protein per day, is often given in liquid form through a tube directly into the stomach, or through a drip into a vein. This high-caloric diet maintenance is required because of the increased metabolic strain brought on by the increased muscle activity.
Tetanus is a global health problem, as C. tetani spores are ubiquitous. The disease occurs almost exclusively in persons who are unvaccinated or inadequately immunized. Tetanus occurs worldwide but is more common in hot, damp climates with soil rich in organic matter. This is particularly true with manure-treated soils, as the spores are widely distributed in the intestines and faeces of many non-human animals such as horses, sheep, cattle, dogs, cats, rats, guinea pigs, and chickens. In agricultural areas, a significant number of human adults may harbour the organism. The spores can also be found on skin surfaces and in contaminated heroin.
Tetanus – particularly the neonatal form – remains a significant public health problem in non-industrialized countries. There are about one million cases of tetanus reported worldwide annually, causing an estimated 300,000 to 500,000 deaths each year.
In the United States, approximately 100 people become infected with tetanus each year, and there are about five deaths from tetanus each year. Nearly all of the cases in the United States occur in unimmunized individuals or individuals who have allowed their inoculations to lapse, whereas most cases in developing countries are due to the neonatal form of tetanus.
Tetanus is the only vaccine-preventable disease that is infectious but is not contagious.