Tetanus, often called lockjaw, is caused by the release of tetanus toxin from a spore-forming bacterium found worldwide in the environment, especially in soil. Tetanus toxin is one of the most potent poisons known.
Unlike other vaccine preventable diseases, tetanus is not transmitted from person to person. Since the toxin is so potent, very low quantities are required to cause disease, Having tetanus does not usually provide future immunity against the disease.
Worldwide, at least one million cases of tetanus need hospital treatment each year. In developing countries, neonatal tetanus (acquired through the umbilical stump) accounts for approximately half these cases. In developed countries, injury causes around 7 out of 10 cases.
Universal infant immunisation with a tetanus toxoid vaccine began in 1960 in New Zealand. Tetanus toxoid is an inactivated form of the toxin.
Almost all the recent cases of tetanus in New Zealand, both adults and children, occurred in individuals who had not received a complete primary course of a tetanus-containing vaccine. A total of 31 tetanus cases were reported from 1997 to 2014; of whom, two adults over 70 years of age died.
Animals, including humans, can carry Clostridium tetani in their intestine and excrete the bacterium and spores with their faeces into the soil. The bacteria and/or spores can be introduced into the body through any wound, no matter how minor. Rural New Zealand children are at greater risk than, a child growing up in very large urban areas with less contact with soil..
Once in the wound, the spores mature into bacteria that releases a toxic chemical (tetanus toxin). The toxin is transported to the central nervous system, preventing the nerve signals that allow muscles to relax to be transmitted.
Wounds that are contaminated or have lots of tissue damage, and deep puncture-type wounds have the highest risk of containing Clostridium tetani. Chronic wounds, such as ulcers, can also be infected. In New Zealand, most cases of tetanus occur following a minor injury.
Initial symptoms, which appear 3-10 days after infection, include weakness, stiffness or cramps and difficulty chewing or swallowing food. As it progresses, tetanus is characterised by muscular rigidity and very painful spasms. A characteristic facial grimace (risus sardonicus) and arching of the back (opisthotonus) occur when the disease is severe.
If left untreated paralysis of the respiratory muscles can cause death.
There is no treatment for tetanus. Management is aimed at reducing the spread and effects of tetanus toxin in the first instance, and supporting the patient as the disease takes its course.
Even with high quality modern intensive care units, machines and medicines, death occurs in approximately 1 in 10 of people who get tetanus.
Everyone who has not received a primary course of three tetanus-containing vaccines is at risk. Anyone born in New Zealand before 1960 is less likely to have received a primary series, unless they were in the armed forces. Older women (who may have missed childhood vaccination) and unvaccinated children appear to be at particular risk.
Since tetanus bacteria are everywhere in the environment and the disease is not transmitted from person to person, community (herd) immunity does not protect individuals.
Vaccination with three or more doses of tetanus-containing vaccine is required for full protection, followed by booster vaccinations throughout life. Booster doses are funded at 11 years, 45 years and 65 years of age.
Boosters may be recommended following injury where the wound is at high risk of being infected with tetanus or if it has been more than 5 years since the last booster.