A bug that causes inflammation in the gut may play a key role in multiple sclerosis (MS), scientists have discovered.
In mice, the bowel bug caused healthy animals to become ill with MS-like symptoms.
Scientists believe it may have a similar effect in humans due to its impact on the immune system.
MS is an auto-immune condition which attacks the fatty insulation around nerve fibres known as myelin.
As the myelin is destroyed, the transmission of nerve messages becomes disrupted, leading to symptoms ranging from mild tingling to paralysis.
The disease affects around 85,000 people in the UK and 2.5 million worldwide.
Anecdotal evidence has suggested that genetically engineered MS-prone laboratory mice fare better in cleaner environments.
Experts have speculated that this might be because of bacteria that affect the development of MS.
The scientists believe that rather than causing MS directly, the bacteria are helping to create the right conditions for the disease to develop.