LONDON, Ontario, Canada—Patients who experience gastrointestinal (GI) symptoms after a bacterial outbreak are more likely to report a diagnosis of arthritis in the ensuing 4 years, but such patients are not more likely to report using prescription medications to treat the joint pain and inflammation, according to new research published online in the journal Rheumatology.¹

"Symptoms of acute gastroenteritis during a bacteria outbreak were associated with new onset arthritis over a subsequent 4 years, however, there was no association with the need for prescription medications for arthritis," conclude researchers led by Amit X. Garg, MD, of London Health Sciences Centre in Ontario, Canada.

The municipal water supply in a small rural town of Southwestern Ontario was contaminated with E. coli 0157:H7 and Campylobacter in May 2000 primarily due to heavy rainfall that transported livestock fecal contaminants into inadequately chlorinated drinking water from a shallow well. As a result, 2300 residents became ill with acute gastroenteritis.

Researchers studied the risk of arthritis after this outbreak. They looked at the relationship between the severity of acute diarrhea and subsequent arthritis symptoms. None of the study participants had a history of arthritis prior to the outbreak.

Dose response seen between arthritis risk and GI symptom severity

Of the 2299 participants, 788 were asymptomatic during the outbreak, 1034 had moderate symptoms of acute gastroenteritis, and 477 had severe symptoms that required medical attention.

The researchers found that 15.7% of participants who had been asymptomatic during the outbreak said they had arthritis after a mean follow-up of 4.5 years after the outbreak. Moreover, 17.6% of participants with moderate symptoms reported arthritis as did 21.6% of those with severe GI symptoms after 4.5 years. Compared with the asymptomatic participants, those with moderate and severe GI symptoms had arthritis at an adjusted relative risk of 1.19.

"This is the largest study to suggest a 'dose response' of diarrhea severity and report of subsequent arthritis," the researches concluded. There was no association observed between gastroenteritis and the subsequent risk of receiving a prescription medication for arthritis, the study showed.

Translating research into practice

J. S. Hill Gaston, MD, rheumatologist at Addenbrookes Hospital in Cambridge England, has studied the mechanisms whereby GI infection can lead to inflammatory arthritis.

"There is no doubt that such infection can induce arthritis," Dr. Gaston said. "The incidence of arthritis after infection varies in different outbreaks, but the authors of this paper didn't directly address this. Instead they questioned patients nearly 2 years after the outbreak."

Dr. Gaston pointed out that the majority of patients who contracted reactive arthritis after infection would be asymptomatic at this stage because reactive arthritis is usually self-limiting. "In addition, in large outbreaks a substantial proportion of patients have arthritis symptoms that are not severe enough to take them to a doctor, so these would not have been detected since the definition used…by a doctor [was] 'you have arthritis.'" Dr. Gaston added, "The small excess of arthritis patients picked up in those with moderate or severe diarrhea may represent those patients who developed a persistent arthritis after infection, but it's hard to be sure from this study."

"If such an outbreak occurred again, physicians might be advised to actively trace those patients with new joint or back inflammation in the 2- to 6-week period following symptomatic infection. These [patients] could then be followed more carefully, possibly typed for HLA-B27 which increases risks of persistence, and treated early with drugs such as sulphasalazine or methotrexate, [although] the evidence for this is limited."

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