Tetanus

The Bacterium

Clostridium tetani, the organism that causes a tetanus infection, is an anaerobic, sport forming, gram-posi-tive bacterium. Its spores are ubiquitous in soil, and are also found in dust and animal feces.

Infection can occur through any open wound: cuts, scrapes, needle injection sites, the umbilical cord, insect bites. The infection rate is higher if the wound is contaminated with soil or caused by wood splinters or dirty, rusty metal. Neonatal tetanus is most often caused by the use of dirty instruments (scissors, clamps, etc.) to cut the umbilical cord.

After the organism enters an open wound, bacterial spores germinate in an anaerobic (low oxygen) environment and release the neurotoxin tetanospasmin. This toxin acts on the myoneuronal (muscle-nerve) junction to inhibit the ability of muscles to relax.

Symptoms

Symptoms of a tetanus infection usually arise one to two weeks after exposure. The tetanus toxin prevents muscles from relaxing, causing a condition known as “spastic paralysis.” In other words, the muscles are locked in the contracted position, leading to a stiff jaw, stiff neck, and the contraction of facial muscles resulting in a sneering expression known as risus caninus.

In newborn children, if tetanus is acquired during delivery, symptoms arise by the end of the first month of life. Symptoms include stiff muscles, fever, and poor feeding.

Muscle spasms, also known as “tetany” are associated with a more advanced stage of the disease and a poor prognosis.

Complications and Prognosis

These muscle spasms can be violent enough to cause spinal fractures. Tetanus has also been associated with abnormal heart rhythms. In adults, with proper treatment, the overall prognosis is good. For children however, prognosis is poor and often results in death. The overall mortality rate of tetanus is 10 percent.

A history of past tetanus infection does not make a patient immune to another infection, so these patients must also be vaccinated.

Treatment & Prevention

Tetanus infections are treated with antibiotics (penicillin or metronidazole) and tetanus antitoxin. The antitoxin is an immunoglobulin that neutralizes tetanospasmin. In severe cases, patients may be unable to breathe independently and they must be place on mechanical ventilation.

The disease can be prevented using a vaccine and by hygienic and sterile wound care and childbirth. In the US, the vaccine is given as the combination vaccine DTaP at 2, 4, 6, and 15 months, and 5 years of age. A booster is then given every 10 years, or after an injury if the last booster was more than 5 years prior. Unvaccinated adults get a three injection series over seven months.

A history of past tetanus infection does not make a patient immune to another infection, so these patients must also be vaccinated. Pregnant women should be vaccinated to pass on some immunity to the newborn child, this can be done while the woman is pregnant. Other countries use different vaccine combinations, including formulations with the hepatitis A and Haemophilus influenzae B (HiB) vaccines.

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