Tetanus is a potentially fatal disease: it acts very quickly and often kills before the body's natural primary response can take place. There are about 1million cases of tetanus a year with between 300,000-500,000deaths. It is a global problem because tetanus spores, which cause the infection, are everywhere. However, due to vaccination programmes, tetanus is rare in the UK with only about 10 cases a year; the main problems are encountered in developing countries where vaccines may be too expensive and equipment may not be properly sterilised.
Friday 26 August 2011
Tetanus – Basic Information & Prevention
Tetanus is caused by gram positive, obligate anaerobic bacteria: Clostridium tetani which affects skeletal muscles."Gram positive" means that the bacteria has a thick cell wall, while "obligate anaerobe" means that the bacteria can't survive in the presence of oxygen and survive using anaerobic respiration (without oxygen). The bacteria releases a neurotoxin called tetanospasmin which binds irreversibly to neurones; these are nerve cells that carry waves of electrical activity, known as nerve impulses. When the toxin binds to the neurone it prevents the inhibition of the motor reflex response to sensory stimuli. The motor reflex response is a rapid response to a stimulus, for example the knee jerk is a motor reflex response to tapping a specific nerve, and in this case it prevents us from falling over. However the toxin stops the nerve from suppressing the movement once the stimuli has gone so the movement continues as a muscle spasm which is characteristic of tetanus.
Causes:
Bacterium Clostridium tetani.
Contamination of a puncture wound, e.g.: a piercing.
Ear infections as bacteria may enter through ear.
Using unsterile equipment in surgery or other similarly invasive procedures such as tattooing and body piercing.
Tetanus is associated with rust which is a little misleading. You are not infected by the rust itself it's just that rust is a rough surface which makes a very good habitat for the endospores of C.tetani. Therefore if you suffer a puncture wound from a rusty object such as a nail, endospores might be delivered into the wound and then you become infected. Endospores are non-metabolising structures that metabolise and cause infection once they are in an adequate environment. Since this bacterium is an obligate anaerobe it can't live in the presence of oxygen, but a puncture wound is a good environment because it is a low oxygen environment.
The disease is common in areas with hot, damp climates that have soil rich in organic matter, or places where soil is treated with manure. This is because the spores of C.tetani are widely distributed in the intestines of animals such as horses, rats, sheep, cattle, dogs and chickens, and therefore are present in manure. Spores can also be found on skin surfaces and in contaminated heroin.
The incubation period for tetanus is usually between 3 and 21 days, so it may be a while before you are aware that you are infected, especially if the site of contamination was a small cut that you were hardly aware of, such as a thorn prick. The further from the central nervous system the contaminated wound is the longer the incubation period. However, the shorter the incubation period the higher the chance of death. Normally symptoms are present after 8 days and they last between 4-6weeks.
Symptoms:
Firstly muscle spasms occur near the wound
Muscle spasm spread to the jaw making it difficult to swallow or open your mouth, hence the name lockjaw
Muscle spasms spread to the face, neck, chest, stomach wall, arms and legs.
Sensitivity to touch
High fever
Sore throat
Rapid heart beat
General tiredness and weakness
Sweating
Can't pass urine
Difficulty with breathing due to chest muscle spasms and lockjaw
Headache
Bleeding into the bowels
Diarrhoea
Direct causes of death include:
Blood poisoning
Suffocation
Cardiac arrest (heart attack)
Kidney failure
Exhaustion.
Complications:
Development of pneumonia and other infections
Fractures of long bones due to severe muscle contractions
Spinal compression fractures
Breathing problems
Coma.
People who are most at risk are:
Over 60s as the vaccine was introduced in the 1960s so they may not be properly immunised
People who aren't immunised or have not had the full vaccination course (tetanus occurs almost exclusively in people who are unvaccinated or inadequately immunised.)
Those who live in poverty where vaccines may not be available or medical treatment is not adequate and equipment isn't properly sterilised.
Intravenous drug users.
There are four different types of tetanus:
Local Tetanus. This is a persistent contraction of the muscles in the same areas as the infected wound. This form is generally mild, but also uncommon.
Cephalic Tetanus. This is a rare form which involves cranial nerves especially in the facial area affecting expressions, breathing and swallowing. It can affect adults with head injuries or children with ear infections as the bacteria enter through the ear.
Generalised Tetanus. This is the most common form accounting for about 80% of cases. The first sign is lockjaw (trismus) and facial spasms (risus sadonicus) followed by a stiff neck, difficulty in swallowing and rigidity in the pectoral and calf muscles. Spasms occur frequently and last several minutes shaping the body into a characteristic posture of an arched and rigid back called opisthotonos. The spasms last for 3-4 weeks and it can take months for a complete recovery.
Neonatal Tetanus. This is generalised tetanus that occurs in newborn babies. They are infected because they haven't obtained passive immunity from their mother because she wasn't immunised. It occurs through the infection of the unhealed umbilical stump, especially if it is cut by unsterilised equipment. Also in some countries it is traditional to put manure on the umbilical stump which can lead to infection. In developing countries this form is responsible for 14% of neonatal deaths but it is rare in developed countries.
You can do blood tests for tetanus but it takes a number of weeks for the body's antibodies to appear in the blood and since tetanus can act quite quickly waiting for blood test results takes too long; a diagnosis is often made on clinical basis. This can usually be diagnosed by the characteristic lockjaw and prolonged muscle contractions of skeletal muscle fibres. Also a spatula test can be done which involves touching the pharynx, which is at the back of the mouth, with a soft-tipped, sterile instrument and observing the results. If there is an involuntary contraction of the jaw, making the person bite down on the spatula then the test is positive and the person has tetanus. A negative result would be a normal gag reflex reaction as the person tries to repel the foreign object from their mouth.
Treatment:
If you suspect that you might be at risk to tetanus you should seek medical help immediately. The wound should be washed clean to remove any dirt and foreign particles from the wound. If it is a particularly dirty or severe wound then dead and infected tissue may be removed by surgery debridement (this involves cutting away the dead tissue).
In mild cases:
Antibiotics such as metronidazole can be prescribed to fight the anaerobic bacteria. It reduces the number of bacteria present but it has no effect on the toxin that the bacteria produce. If metronidazole isn't available penicillin may be prescribed but it is not as effective. If you aren't sure when you had your last tetanus vaccine or have not had a complete course of immunisation then you may be given a booster shot, however this will not prevent potentially fatal cases of tetanus as it takes up to 2 weeks to develop tetanus antibodies to fight the bacteria. Diazepam, also known as valium, can be given as a muscle relaxant.
Passive immunisation with anti-tetanospasmin immunoglobulin is vital. Immunoglobulins are antibodies and form part of the body's immune response. In this case the immunoglobulin used is an antitoxin which means it blocks the toxins released by bacteria. The antibodies are taken from blood donors who have recently been vaccinated against tetanus and inserted into a vein or muscle (intravenously or intramuscular injections). These provide immediate protection, however they are only temporary because it is a form of artificial passive immunity and the body's own immune cells haven't produced the antibodies so memory cells aren't made therefore if there is a second exposure then the body will still have to make its own antibodies which take time. Also the body regards the donated antibodies as foreign and they are removed from the circulation and destroyed in the liver and spleen.
In severe cases:
This must be treated in an intensive care unit in hospital. Injecting immunoglobulins is important as it increases clinical improvement from 4 to 35%. Maintaining an open airway is vital; in some cases a tracheostomy is performed which involves creating a hole in the neck through to the windpipe and inserting a tube in to allow you to keep breathing freely although your mouth or throat may be blocked higher up, you may be supported on mechanical ventilation for 3-4weeks. In very severe cases the patient may have to be paralysed and supported on mechanical ventilation.
Magnesium can be given as intravenous injection as this prevents muscle spasms, diazepam may also be given as it is a muscle relaxant.
Proper nutrition is required: 3500-4000 calories are needed every day with at least 150g of protein a day. The amount must be so high because of the increased metabolic strain caused by the increased muscle activity of spasms. It can often be given in liquid form through tubes directly into the stomach or through a drip into a vein.
Prevention:
The best prevention against tetanus is proper immunisation as tetanus occurs almost exclusively in people who are unvaccinated or inadequately immunised. In the UK the vaccination is included in children's vaccination programmes and is part of the combined diphtheria/tetanus/polio/haemophilus influenza b vaccine. For adults and teenagers it is included in the tetanus/diphtheria/polio vaccine. The vaccination course involves 5 doses of vaccinations: the primary course is given as 3 separate doses each a month apart, normally it is given to babies, starting when they are two months old, but it can be given to adults as well. In children the fourth dose is given three years after their primary course, in adults it is administered ten years after the primary course. Finally the fifth dose is given ten years after the fourth. The primary course provides protection for a number of years while the fourth and fifth doses maintain this protection and should last a life-time. Vaccinations inject a small amount of dead or harmless bacteria into the blood, which the body recognises as foreign. The body's immune system then produces antibodies to destroy these foreign particles and at the same time memory cells are made so that if there is a second exposure (if you actually were infected by tetanus) your immune response would be much quicker and more effective. After the vaccine it is normal to feel slightly unwell with symptoms including mild headache, aching muscles and mild fever which last a few days. You should not have the vaccine if you already have an illness causing a fever or if your last tetanus vaccination caused a severe reaction although this is very rare. It is safe to have the vaccine if you are pregnant or breast feeding.
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