A type of bacteria often found in milk and beef could trigger the development of rheumatoid arthritis in some people, according to a new study.
Rheumatoid arthritis is a long-term condition that causes pain, swelling and stiffness in the joints. The symptoms usually affect the hands, feet and wrists.
The research, from the University of Central Florida, suggests there could be a link between Mycobacterium avium subspecies paratuberculosis, [MAP] and rheumatoid arthritis in people who are genetically at risk of developing the disease.
MAP, which can be found in about half the cows in the United States, can be spread to humans through the consumption of infected milk, beef and produce fertilized by cow manure.
The study, which was published in the Frontiers in Cellular and Infection Microbiology journal this week, was a collaboration between Saleh Naser, UCF infectious disease specialist, Dr. Shazia Bég, rheumatologist at UCF's physician practice, and Robert Sharp, a biomedical sciences doctoral candidate at the medical school.
After discovering a connection between MAP and Crohn's disease, Naser wanted to investigate MAP and rheumatoid arthritis - as both conditions share the same genetic predispositions, and are often treated using the same types of drugs.
Naser said: "Here you have two inflammatory diseases, one affects the intestine and the other affects the joints, and both share the same genetic defect and treated with the same drugs.
"Do they have a common trigger? That was the question we raised and set out to investigate."
In order to investigate, Bég recruited 100 of her patients to voluteer clinical samples to test.
They found that 78 percent of the patients with rheumatoid arthritis had the same genetic mutation found in Crohn's patients.
"40 percent of that number tested positive for MAP."
Naser said: "We believe that individuals born with this genetic mutation and who are later exposed to MAP through consuming contaminated milk or meat from infected cattle are at a higher risk of developing rheumatoid arthritis."
Bég added: "We don't know the cause of rheumatoid arthritis, so we're excited that we have found this association.
"But there is still a long way to go. We need to find out why MAP is more predominant in these patients - whether it's present because they have RA, or whether it caused RA in these patients.
"If we find that out, then we can target treatment toward the MAP bacteria."
The team is conducting further studies.