Travelers' Diarrhea: Antimicrobial Therapy and Chemoprevention

Herbert L DuPont

Disclosures

Nat Clin Pract Gastroenterol Hepatol. 2005;2(4):191-198. 

In This Article

Summary and Introduction

Summary

The use of preventive measures and self-treatment for travelers' diarrhea is routine in regions where the occurrence of diarrhea is predictably high. People traveling to these areas who do not exercise care in their selection of consumed foods and beverages will suffer high rates of illness. Such diarrhea normally affects the traveler for a day, although it can result in chronic postinfectious irritable bowel syndrome. Although systemic antibacterial drugs are effective in preventing diarrhea, their use is not routinely recommended because of side effects and their importance as a therapy for extra-intestinal infections. This review focuses on current and future uses of antibacterial drugs in the prevention and therapy of travelers' diarrhea. Minimally absorbed (<0.4%) rifaximin can effectively reduce the occurrence of travelers' diarrhea without side effects. Bismuth subsalicylate is a useful alternative, although it is less effective than rifaximin for the prevention of travelers' diarrhea and the required doses are less convenient. All people who travel to high-risk areas should take curative antimicrobial agents with them for self-treatment of illness: rifaximin 200 mg three times a day for 3 days, or an absorbable agent such as a fluoroquinolone or azithromycin taken in a single dose initially, with the need for a second or third dose determined by clinical response. Loperamide (up to 8 mg per day for ≤2 days) can be given with the antibiotic to offer rapid symptomatic improvement. In the future, the ability to evaluate the genetic risk of illness acquisition might allow person-specific recommendations to be made.

Introduction

Approximately 20 million episodes of diarrhea occur annually in people traveling from industrialized regions to developing countries. The world can be divided into three regions depending upon the risk of acquiring travelers' diarrhea for visitors from industrialized and low-risk regions (Figure 1).

Figure 1.

A map of the world depicting expected rates of diarrhea among international travelers from low-risk areas.

The success of antibacterial chemoprophylaxis in treating diarrhea provided the first evidence that bacteria are responsible for most episodes of the illness.[1] Studies demonstrating that antibacterial drugs were effective in the treatment of travelers' diarrhea were first carried out in 1980 and 1981, with each study published 2 years later.[2,3]

Thanks to microbiology studies[4] and the response of patients to antibacterial treatment, we now know that about 80% of cases of travelers' diarrhea are due to bacterial agents. There are three main causes of diarrhea. Diarrheogenic Escherichia coli, including enterotoxigenic E. coli and enteroaggregative E. coli, is responsible for ~50% of cases. The invasive bacterial pathogens Campylobacter jejuni, Shigella, Salmonella and invasive E. coli cause ~10-25% of cases, with the highest frequencies in southern Asia.[4,5] In ~20% of cases no pathogen is detectable; because they seem to be both treated and prevented by antibacterial drugs,[3,7,8,9] most of these cases are caused by undefined bacterial pathogens.[6] In coastal areas of the world, non-cholera Vibrio species cause a small percentage of diarrhea. V. cholerae can cause travelers' diarrhea in epidemic areas but cholera is rare in international travelers.

Regardless of cause, most cases of travelers' diarrhea have a similar clinical appearance, with patients complaining of watery diarrhea with abdominal pain or cramps of variable severity. Fever and dysentery (gross blood in stool) are infrequent and are documented in 1-3% of cases.[10,11,12] Illness generally incapacitates the traveler for about 1 day.[13] Diarrhea persists for more than 2 weeks in ~2-10% of cases[14] and as many as 10% of patients develop what is now recognized as postinfectious irritable bowel syndrome (IBS).[15] With postinfectious IBS, chronic gastrointestinal complaints occur with abdominal discomfort or pain that can be relieved by defecation and/or a change in bowel pattern and stool form (intermittent diarrhea and constipation), bloating, abdominal distention, passage of mucus, fecal straining, urgency or feeling of incomplete evacuation.

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