Tetanus is an infectious disease caused by contamination of wounds from the bacteria Clostridium tetani, or the spores they produce that live in the soil, and animal feces. Tetanus has been recognized for centuries; the term is derived from the ancient Greek words tetanosand teinein, meaning taut and stretched, which describe the condition of the muscles affected by the toxin, tetanospasm, produced by Clostridium tetani.
The causative bacterium, Clostridium tetani, is a hardy organism capable of living many years in the soil in a form called a spore. The bacterium was first isolated in 1889 by S. Kitasato while he was working with R. Koch in Germany. Kitasato also found the toxin responsible for tetanus and developed the first protective vaccine against the disease.
Tetanus occurs when a wound becomes contaminated with Clostridium tetani bacterial spores. Infection follows when spores become activated and develop into gram-positive bacteria that multiply and produce a very powerful toxin (tetanospasmin) that affects the muscles. Tetanus spores are found throughout the environment, usually in soil, dust and animal waste.
The usual locations for the bacteria to enter the body are puncture wounds, such as those caused by rusty nails, splinters, or insect bites. Burns, any break in the skin, and IV drug access sites are also potential entryways for the bacteria. Tetanus is acquired through contact with the environment; it is not transmitted from person to person.
Tetanus results in severe, uncontrollable muscle spasms. For example, the jaw is "locked" by muscle spasms, causing the disease to sometimes be called "lockjaw". In severe cases, the muscles used to breathe can spasm, causing a lack of oxygen to the brain and other organs that may possibly lead to death.
The disease in humans is the result of infection of a wound with the spores of the bacteria Clostridium tetani. These bacteria produce the toxin (poison) tetanospasmin, which is responsible for causing tetanus.
Tetanospasmin binds to motor nerves that control muscles, enters the axons (filaments that extend from nerve cells), and travels in the axon until it reaches the body of the motor nerve in the spinal cord or brainstem (a process termed retrograde intraneuronal transport).
Then the toxin migrates into the synapse (small space between nerve cells critical for transmission of signals among nerve cells) where it binds to presynaptic nerve terminals and inhibits or stops the release of certain inhibitory neurotransmitters (glycine and gamma-aminobutyric acid).
Because the motor nerve has no inhibitory signals from other nerves, the chemical signal to the motor nerve of the muscle intensifies, causing the muscle to tighten up in a huge continuous contraction or spasm. If tetanospasmin reaches the bloodstream or lymphatic vessels from the wound site, it can be deposited in many different presynaptic terminals resulting in the same effect on other muscles.
In the United States, because of widespread immunization and careful wound care, the total annual number of cases has averaged about 40-50 cases per year since 1995. In developing countries of Africa, Asia, and South America, tetanus is far more common. The annual worldwide incidence is between 500,000-1 million cases. The majority of new cases worldwide are in neonates in third-world countries.
- The disease can show four possible types:
- Generalized tetanus can affect all skeletal muscles. It is the most common as well as the most severe form of the four types.
- Local tetanus manifests with muscle spasms at or near the wound that has been infected with the bacteria.
- Cephalic tetanus primarily affects one or several muscles in the face rapidly (in one to two days) after a head injury or ear infection. Trismus ("lockjaw") may occur. The disease can easily progress to generalized tetanus.
- Neonatal tetanus is similar to generalized tetanus except that it affects a baby that is less than 1 month old (called a neonate). This condition is rare in developed countries.
The hallmark feature of tetanus is muscle rigidity and spasms.
- In generalized tetanus, the initial complaints may include any of the following:
- Irritability, muscle cramps, sore muscles, weakness, or difficulty swallowing are commonly seen.
- Facial muscles are often affected first.Trismus or lockjaw is most common. This condition results from spasms of the jaw muscles that are responsible for chewing. A sardonicsmile - medically termed risussardonicus - is a characteristic feature that results from facial muscle spasms.
- Muscle spasms are progressive and may include a characteristic arching of the back known as opisthotonus. Muscle spasms may be intense enough to cause bones to break and joints to dislocate.
- Severe cases can involve spasms of the vocal cords or muscles involved in breathing. If this happens, death is likely, unless medical help (mechanical ventilation with a respirator) is readily available.
- In cephalic tetanus, in addition to lockjaw, weakness of at least one other facial muscle occurs. In two-thirds of these cases, generalized tetanus will develop.
- In localized tetanus, muscle spasms occur at or near the site of the injury. This condition can progress to generalized tetanus.
- Neonatal tetanus is identical to generalized tetanus except that it affects the newborn infant. Neonates may be irritable and have poor sucking ability or difficulty swallowing.
Clostridium tetani is a gram-positive rod-shaped bacterium that is found worldwide in soil; it is usually in its dormant form, spores, and becomes the rod-shaped bacterium when it multiplies. The vegetative rods produce the spore usually at one end of the rod. The organisms are considered anaerobic.
- Clostridium tetani is the bacterium responsible for the disease. The bacteria are found in two forms: as a spore (dormant) or as a vegetative cell (active) that can multiply.
- The spores are in soil, dust, and animal waste and can survive there for many years. These spores are resistant to extremes of temperature.
- Contamination of a wound with tetanus spores is rather common. Tetanus, however, can only occur when the spores germinate and become active bacterial cells.
- The active bacterial cells release two exotoxins, tetanolysin and tetanospasmin. The function of tetanolysin is unclear, but tetanospasmin is responsible for the disease.
- The disease typically follows an acute injury or trauma that results in a break in the skin. Most cases result from a puncture wound, laceration (cut), or an abrasion (scrape).
- Other tetanus-prone injuries include the following:
- crush wound,
- IV drug users (site of needle injection).
- Wounds with devitalized (dead) tissue (for example, burns or crush injuries) or foreign bodies (debris in them) are most at risk of developing tetanus.
- Tetanus may develop in people who are not immunized against it or in people who have failed to maintain adequate immunity with active booster doses of vaccine.
Medical treatment has two aims: limit growth and eventually kill the infecting C. tetani and thus eliminate toxin production; the second aim is to neutralize any toxin that is formed. If the toxin has already affected the patient, the two aims are still important, but supportive measures will be needed for the patient.
These steps are outlined below:
- Antibiotics (for example, metronidazole [Flagyl, Flagyl 375, Flagyl ER], penicillin G or doxycycline [Adoxa, Alodox, Avidoxy, Doryx, Monodox, Oracea, Oraxyl, Periostat, Vibramycin, Vibramycin Calcium, Vibramycin Monohydrate, Vibra-Tabs]) to kill the bacteria, tetanus booster shot, if necessary, and occasionally, antitoxin (termed tetanus immune globulin or TIG) to neutralize the toxin.
- Wound cleansing to remove any obvious bacteria collections (abscesses) or foreign bodies; if the patient is exhibiting any toxin-related problems, TIG is usually administered first and wound care is delayed for a few hours while the TIG neutralizes toxin because infected wounds, when manipulated, may release more toxin.
- Supportive measures.
- Pain medicine as needed.
- Sedatives such as diazepam (Valium) to control muscle spasms and muscle relaxants.
- Ventilator support to help with breathing in the event of spasms of the vocal cords or the respiratory muscles.
- IV rehydration because, as muscles spasm constantly, increased metabolic demands are placed on the body.