Scientists have identified a type of bacteria they believe may cause Crohn's disease.
The condition may be passed on through milk
The bowel disorder affects 100,000 Britons and can cause a variety of symptoms, ranging from a lack of appetite to chronic diarrhoea and abdominal pain.
Its cause is unknown, although one theory is that it can be passed to humans in milk, suggesting that it may be caused by a bacterium.
This discovery of a type of bacteria in patients with the disease will raise hopes of better treatments to fight the condition.
Professor John Hermon-Taylor and colleagues at St George's Hospital Medical School in London carried out tests on a group of patients with Crohn's disease.
They also carried out tests on another group without the condition.
They found Mycobacterium avium paratuberculosis (MAP) bacteria in 92% of patients with the disease.
However, they only found the bacteria in 26% of patients without the condition.
This has led the scientists to suggest that this bacteria may play a key role in causing the disease.
"The rate of detection of MAP in individuals with Crohn's disease is highly significant and implicates this pathogen in disease causation," said Professor Hermon-Taylor.
"The problems caused by the MAP bug are a public health tragedy," he said.
Professor Hermon-Taylor said an unexpected finding of the research showed that patients suffering from irritable bowel syndrome (IBS) may also be infected with MAP.
IBS is painful and can cause diarrhoea, or diarrhoea alternating with constipation.
Sufferers often desperately need to go to the toilet with little warning, which severely limits their lifestyle.
No-one knows what causes IBS, although it is suggested that stress can make it worse. More women are affected than men.
"In animals, MAP inflames the nerves of the gut," Professor Hermon-Taylor said.
"Recent work from Sweden shows that people with IBS also have inflamed gut nerves.
"There is a real chance that the MAP bug may
be inflaming people's gut nerves and causing IBS."
The findings are published in the Journal of Clinical
Microbiology. Professor Hermon-Taylor said he has sent a copy of the paper to Sir Liam Donaldson, chief medical officer for England.
The research was welcomed by the medical charity Action Research.
It said that previous studies have suggested that MAP is found in 2% of retail pasteurised milk cartons.
"The discovery that the MAP bug is present in the vast
majority of Crohn's sufferers means it is almost certainly causing the intestinal inflammation," it said in a statement.
"Action Research does not recommend that anyone stops drinking milk.
"However, for those individuals with Crohn's
disease or their close relatives who may feel particularly at risk, it may be sensible to start drinking UHT milk.
"As UHT involves higher pasteurisation temperatures, it is probable that MAP is destroyed," it said.
The charity called for Crohn's to be made a reportable disease, for more stringent milk pasteurisation, for tests for MAP in dairy herds, and procedures for reducing MAP infection on farms.