A strain of bacteria commonly found in beef and milk may be a trigger for developing rheumatoid arthritis (RA) in individuals who are genetically at risk, according to researchers at the University of Central Florida (UCF) in the United States.

The bacteria – Mycobacterium avium subspecies paratuberculosis (MAP) – is found in about half the cows in the US. The bacteria can be spread to humans through consumption of infected milk, beef, and produce fertilised by cow manure.

The new UCF findings by infectious disease specialist Dr Saleh Naser and rheumatologist Dr Shazia Beg, published in the journal Frontiers In Cellular And Infection Microbiology, are the first to connect the dots between MAP and RA, an autoimmune disease that attacks joints, muscles, bones and organs.

The research was inspired by – and builds upon – previous work by Dr Naser that linked MAP with the chronic inflammatory condition of the gastrointestinal tract, Crohn’s disease.

“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,” Dr Naser said. “Do they have a common trigger? That was the question we raised and set out to investigate.”

Dr Beg recruited 100 of her patients for the study. Subjects volunteered clinical samples for testing. Of the patients with RA, 78% were found to have a mutation in the PTPN2/22 gene, the same genetic mutation found in Crohn’s patients, and 40% of that number tested positive for MAP.

“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,” Dr Naser said.

Researchers said that further study is needed. “We don’t know the cause of rheumatoid arthritis, so we’re excited that we have found this association,” Dr Beg said.

“But there is still a long way to go,” she adds. “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.” – New York Daily News/Tribune News Service