It’s a familiar enough scenario.
You step on a rusty nail, or your child appears with a puncture wound sustained while playing outdoors.
You immediately imagine tetanus infection and rush off to the local doctor or emergency department for treatment.
The doctor wants to give a tetanus injection, and you agree because you don’t know much about tetanus except it is connected to rusty nails and causes lockjaw.
It’s important to understand what tetanus is and the best course of treatment for possible exposure.
What Is Tetanus?
There’s a common misconception that rust causes tetanus. In fact it is caused by the bacteria Clostridium tetani. These bacteria are found everywhere in the natural environment. Spores can be found in soil and dust, and in animal and human intestines and faeces.
Tetanus is not a contagious disease and can’t be passed from person to person. The bacteria are often introduced into the body through puncture wounds, burns, deep flesh wounds, needle punctures from drug use, bites or scratches from animals, or other wounds that are contaminated by human and animal faeces or saliva.
It’s important to note the difference between the vegetative and spore state of C. tetani:
Vegetative State
In a vegetative state, C. tetani is anaerobic, which means it lives in the absence of oxygen. At this stage, it produces toxins that cause tetanus infections. In a vegetative state, C. tetani is heat sensitive and will die if exposed to oxygen.
Spore State
In the spore state, C. tetani is very tough, and consists of a core which has only the bare essentials ready to begin bacterial growth. The spore basically protects C. tetani bacteria from conditions that would normally kill it in a vegetative state.
In the spore state, C. tetani can survive oxygenated environments, heating and disinfectants. In this state, when C. tetani is introduced into an anaerobic environment, such as dead or injured tissue, the spores can germinate to the vegetative form, which causes tetanus infections.
What Does Tetanus Do?
Once the tetanus bacteria find their way into the body through an open wound, if the spores survive, they begin to germinate. The spores then produce two toxins:
- Tetanolysin, which damages the healthy tissue around the infection and creates anaerobic conditions for the spores to germinate in.
- Tetanospasmin, which is a powerful neurotoxin. It’s estimated only 240 grams would be needed to kill the entire world population. Its effects are very specific and irreversible; recovery only occurs through the growth of new nerve cells.
When tetanus has been introduced into the body, there is a period of incubation when the spores wait for conditions to be optimal for germination. When germination has occurred, the toxin secretions begin to build up.
At this stage, it’s not possible to see infection in the wound, and often the injury has healed by the time tetanus symptoms begin.
The incubation period is about one week from injury, with the length of incubation being related to the distance between the wound and the central nervous system: e.g. the incubation period after a cut on the finger will be longer than after a head wound.
Tetanospasmin spreads through the body via the central nervous system, interfering with messages to the brain (neurotransmitters). This leads to symptoms such as muscle stiffness, rigidity and spasms. In severe cases it can cause seizures.
Multiple Types Of Tetanus
A little known fact about C. tetani is it produces four clinical types of tetanus, each with slightly varying symptoms:
- Generalised type: the most common form, causing about 80% of all tetanus infections. The toxins travel through the body through the lymphatic and vascular systems, spreading further and affecting more nerves. This type normally begins at the top of the body and moves down, with the first signs being lockjaw and facial spasms, followed by stiffness of the neck, difficulty swallowing; then the chest muscles are affected. Other possible symptoms are fever, irregular heartbeat and involuntary muscle spasms
- Localised type: contractions and spasms occur near the site of the injury. This is a milder, less threatening form of tetanus, with a fatality rate of 1%. Treatment is necessary to prevent the condition developing into generalised tetanus.
- Cephalic type: affects the cranial nerves, and commonly happens after injuries such as ear infections and head trauma. It causes extreme pain as it affects the muscles of eyelids, tongue and lips.
- Neonatal type: occurs in newborns, commonly in developing countries where babies are born in unhygienic conditions, and is often the result of an infection of the umbilical stump. Progression of this infection is typically very fast, and has a fatality rate of about 90%.
How Likely Is Tetanus Infection?
Based on the facts, tetanus infection is very unlikely to occur in situations that are usually associated with the bacteria.
Infection by the most common type of tetanus requires a wound which is deep enough not to bleed or to be exposed to oxygen, so the spores can survive and germinate.
Oxygenation occurs when we bleed from a wound. Oxygen is added as blood passes through our lungs, before being transported around our bodies. If we’re injured and the wound bleeds copiously and freely, oxygen is present and C. tetani can’t survive.
In most cases where tetanus infection occurs, it’s due to improper wound care.
Neonatal tetanus occurs in developing countries, where birth equipment might not be sterile, and cord care of the umbilical stump isn’t hygienic.
Diabetes is a leading factor in the likelihood of developing tetanus. Diabetics have poor circulation, which prevents healthy wound healing. According to the Centers For Disease Control And Prevention (CDC), in the US from 1987 to 2008, diabetics accounted for 13% of all reported tetanus cases and 29% of all tetanus deaths. The incidence of tetanus among diabetics was more than three times that among non-diabetics.
Elderly populations have lowered immune systems and are more likely to have circulatory disorders, making them more likely to be infected by tetanus. The CDC reports the risk of dying from tetanus is five times greater in people 65 years or older.
Intravenous drug use also increases the risk of developing tetanus. The CDC reports intravenous drug users accounted for 15% of tetanus cases from 2001 to 2008.
If you have concerns about being infected by C. tetani, the only way to get a diagnosis is to have a clinical examination. Your doctor will look for obvious signs of tetanus infection, such as muscle stiffness, spasms and pain.
There is no laboratory test available to test and diagnose for tetanus infection.
Treatment Of Tetanus Infection
If tetanus infection is diagnosed, there is a multiple treatment approach:
- Prevent further toxin release: this involves cleaning the wound, removing any dead tissue and giving antibiotics to kill the bacteria
- Neutralise unbound toxin: tetanus immunoglobulin, or tetanus antitoxin, is injected to neutralise the toxin which is not yet in the central nervous system.
- Minimise effects of bound toxin: there is no way to deactivate bound toxin and reverse the damage already done, except to wait for growth of new nerve cells, which can take several weeks. During this time, symptoms are managed with sedation, anticonvulsants, neuromuscular blocking agents, and mechanical ventilation.
What About The Tetanus Vaccine?
If a member of your family is admitted to hospital with an injury, one of the first things doctors will ask about is tetanus vaccine status. They will probably insist on administering a tetanus booster as a form of treatment.
There are a few very important things to know about the tetanus vaccine, which most parents and many care providers aren’t aware of:
- There is no single tetanus vaccine. It’s given as a combination of diphtheria, tetanus and pertussis (DTaP). If you wish to avoid the diphtheria and pertussis component of the vaccine, it’s probably not possible.
- The vaccine can take several weeks to create antibodies against tetanus. If tetanus has been introduced into a wound, this would be too long to prevent infection from occurring.
- The CDC states the efficacy of the tetanus toxoid has never been studied in a vaccine trial.
What Can I Do For A Potential Tetanus Injury?
The most important thing to remember, if you are concerned about tetanus infection, is to seek medical assistance as quickly as possible after the injury has occurred.
There several common recommendations for care of wounds to prevent tetanus infection. Unfortunately, a deeper understanding of how tetanus survives shows these recommendations offer little help.
#1: Let The Wound Bleed
While C. tetani in the vegetative state can’t survive in oxygenated environments, the spores can. If an injury bleeds, the spores can still be introduced into the wound and find dead tissue, where they can germinate and produce toxins.
#2: Use Hydrogen Peroxide
Hydrogen peroxide has been used as an antiseptic for almost 100 years. When applied to an open wound it fizzes and bubbles, which happens as the peroxide comes into contact with an enzyme called catalase.
But the antiseptic can’t differentiate between healthy cells and bacteria cells. Using hydrogen peroxide on a wound might kill healthy cells, creating the perfect environment for tetanus spores to germinate.
#3: Clean The Wound
Wound cleaning generally isn’t a bad thing, but it won’t necessarily kill off any tetanus spores lurking in injuries. Wounds begin the healing process not long after the injury has occurred, so cleaning might not reach all the affected tissue.
What Else Can I Do After An Injury?
If someone in your family is at risk for tetanus infection due to an injury, you can request prophylactic treatment with the human tetanus immunoglobin (TIG) injection.
It’s important to ensure the TIG is from human plasma, not from animal blood, as human TIG confers much longer protective immunity and causes fewer adverse reactions than animal TIG.
