• Improvement in IBS Global Improvement Scale. [ Time Frame: once a month for the 6 months following completion of medication ] [ Designated as safety issue: No ]
  

• Change in Symptom Severity [ Time Frame: 6 months after medication regimine is completed ] [ Designated as safety issue: No ]
  
• Change in IBS-QOL Questionnaire [ Time Frame: 1 week after starting the medication, 2 weeks after starting the medication, 1 month after finishing medication, 6 months after finishing medication ] [ Designated as safety issue: No ]
  
• Change in LBT [ Time Frame: 6 months after completion of medication ] [ Designated as safety issue: No ]
  

Approximately 700,000 United States military personnel were deployed in the first Persian Gulf (PG) War. Several months after their return, up to 25% of Veterans had persistent symptoms which they suspected were related to their military service in the Gulf. Among the most frequent were gastrointestinal symptoms such as loose stools, excessive gas and abdominal pain. These symptoms are typical of diarrhea-predominant irritable bowel syndrome (IBS).

The cause of IBS is not known; speculated mechanisms include altered GI motility, bacterial overgrowth, visceral hypersensitivity and psychological stress. Another proposed mechanism relates to the fact that up to one third of patients with IBS describe the onset of their symptoms following acute gastroenteritis. This is called post-infective IBS (PI-IBS). How acute gastroenteritis leads to persistent GI symptoms of IBS is not known. A limited amount of data suggests that patients with IBS may have an imbalance in their gastrointestinal microflora. Several studies indicate that small bowel bacterial overgrowth is more common in individuals with IBS. Symptoms of SBBO are similar to diarrhea-predominant IBS and include chronic diarrhea, bloating and abdominal pain. More than 50 percent of military personnel developed acute gastroenteritis while on duty in the Gulf. Most of them who reported symptoms of IBS had an acute onset which occurred in association with an episode of acute gastroenteritis during their tour of duty. Other travelers are known to be colonized by new micro-organisms during travel to foreign countries. This acquisition is thought to be related to a change in diet. The natural history of this change in bowel flora, in part, depends on host factors and can persist for months after travel abroad. It seems likely, that PG veterans with persistent diarrhea and a negative work-up for known GI diseases have PI-IBS. No study in the past has evaluated the role of SBBO in causing chronic GI symptoms in PG Veterans. Furthermore, soldiers involved in combat are exposed to a highly stressful environment, perhaps making them more susceptible to persistent symptoms. We hypothesize that PG veterans with chronic GI symptoms have symptoms of diarrhea predominant IBS and this is caused by SBBO due to a change in microflora during deployment in the Persian Gulf and that it is predisposed to by the stress of combat. Intestinal microflora, once altered, is known to be relatively stable; once mucosal damage occurs it may become permanent.

Objectives Objective # 1: Estimate the burden of disease due to chronic gastrointestinal illness in PG veterans.

Hypothesis:

i. The prevalence of GI symptoms is high in PG veterans. ii. The prevalence of IBS is higher in veterans who report acute gastroenteritis during the period of deployment.

iii. PG Veterans with IBS have a lower IBS related QOL

Objective # 2: Evaluate whether SBBO is associated with chronic diarrhea in PG veterans.

Hypothesis i. SBBO is more common in PG veterans than non deployed veterans. ii. SBBO is more common in PG veterans with diarrhea-predominant IBS vs. those without.

Objective: # 3: Determine whether eradication of SBBO reduces symptoms of chronic diarrhea, abdominal pain and bloating in PG Veterans.

Hypothesis:

i. Treatment with rifaximin, a non-absorbable antibiotic, will improve symptoms and QOL in Veterans with SBBO.