Parkinson’s disease could be caused by an infection with tetanus bacteria, according to a radical new idea.
The claim stems from the finding that people who have recently been vaccinated against tetanus to prevent a wound infection are half as likely to later be diagnosed with Parkinson’s. “The closer to the vaccine date, the less likely individuals are to get diagnosed with Parkinson’s disease,” says at Tel Aviv University in Israel.
The results suggest that widely available tetanus vaccines could prevent or treat Parkinson’s, although first they need to be repeated. If confirmed, “it’s big news,” says Israel. “I really hope that it will change the way we understand and treat the disease.”
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Parkinson’s disease is a neurodegenerative condition that usually affects older people and involves tremors and difficulties in moving. It is caused by progressive death of a subset of brain cells that control movement, but its trigger is unknown.
The researchers analysed the records of a large health provider in Israel to see if any kind of vaccines given in adulthood were linked with a raised or lower risk of Parkinson’s. They picked nearly 1500 people who had been diagnosed at between 45 and 75 years old, then compared them with a five-fold larger control group, selected to have similar characteristics as those with the condition.
They found that 1.6 per cent of people with Parkinson’s had a record of having the tetanus vaccine before their diagnosis, compared with 3.2 per cent of those without the condition. The protective effect was also bigger in those who had the vaccine more recently, with no one developing Parkinson’s within two years of being immunised.
In Israel, as in many countries, adults generally get a tetanus vaccine if they have a wound contaminated with soil, faeces or saliva, as the bacterium that causes the disease, Clostridium tetani, can be found in these substances. If this pathogen infects a wound, it can lead to debilitating muscle spasms and even death.
Adding to the link with Parkinson’s, C. tetani is known to release a toxin that damages nerve cells. In fact, it is the effects of this toxin that cause the characteristic muscle spasms after tetanus infection of a wound.
The tetanus vaccine is an altered version of this toxin, which causes the immune system to make antibodies that are also effective against the real toxin.
C. tetani can live harmlessly in the human gut and Israel speculates that Parkinson’s may arise if it somehow transfers to the nose, where any toxins released could travel up nerve cells to the brain.
“We know that this toxin can travel along the neurons,” he says. “I do not think that the mere presence of Clostridium tetani somewhere in the microbiome is sufficient to cause the disease. There are probably some other factors, like genetic factors, that cause some people to be particularly sensitive to the damage caused by the toxin.”
at the University of Cambridge says the analysis considered quite small numbers of people when comparing those who had their vaccine at different intervals before they developed Parkinson’s. “That makes it hard to draw firm conclusions,” he says. “But I think it’s interesting and worth looking at in other populations.”
at the charity Parkinson’s UK says the findings raise “the interesting possibility that tetanus vaccinations could have the potential to offer protection against the development of Parkinson’s and may even be able to slow progression of the condition. As this is something current treatments can’t do, this would be hugely significant if realised.”
MedRxiv
