5 Traveler's Diarrhea

With increasing economic globalization and the increased popularity of tourism to developing nations, travelers’ diarrhea affects literally millions of travelers each year. A generally accepted definition for travelers’ diarrhea is the passage of three or more loose to diarrheal stools in 24 hours often but not invariably associated with other symptoms, including abdominal discomfort, nausea, vomiting, hematochezia, and fever, depending on the cause. Symptoms most often develop 2-10 days after arrival of the traveler but may occur at any time during foreign exposure.

The incidence of travelers’ diarrhea varies greatly with geographic region and correlates with the level of sanitation at the travelers’ destination. Incidence rates as high as 50% have been noted for selected Asian, Central African, and Latin American countries whereas estimated rates are 10-20% in Southern European countries, the Caribbean Islands, and Northern African countries. Estimated rates among travelers to and in Northern Europe, the United States and Canada, Australia, and New Zealand are well under 10%. Risk factors for the individual traveler other than destination are conditions that interfere with host defenses against enteric infections, as discussed earlier in this chapter. In particular, immunosuppressed patients and patients with hypochlorhydria caused by pharmacologic agents or gastric surgery may be especially vulnerable to developing traveler’s diarrhea.

Virtually any of the specific organisms discussed individually in this chapter may be the causative agent for any given case of traveler’s diarrhea. Pathogenic bacteria have been estimated to cause up to 90% of traveler’s diarrhea in some studies in which an etiologic agent was identified. ETEC and EAEC appear as the most common causes, but invasive bacteria including Campylohacter, Salmonella, Shigella species, and invasive E coli predominate among those with dysentery. Both rotaviruses and noroviruses are established causes, the latter being increasingly recognized among cruise passengers. Protozoa, while less common, have been isolated from a substantial number of travelers with more protracted diarrhea, especially among those who develop malabsorption.

The clinical features will not be belabored here and the reader is referred to the descriptions of specific infections earlier in the chapter. By far the most common presentation is that associated with ETEC or EAEC infection, with abrupt onset of watery diarrhea lasting a few hours to as long as 5 days. However, the entire spectrum of the clinical features of gastrointestinal infections may be seen, ranging from a few loose stools to severe dysentery with fever or protracted diarrhea with malabsorption, depending on the cause of the infection and the host’s immune response capacity.

Because a specific diagnosis is rarely established during travels, treatment is largely empiric. If diarrhea is severe, rehydration is crucial, preferably using an oral rehydration solution with a formula similar to that recommended by the WHO or, if necessary, intravenous hydration. Loperamide (2 mg up to four times daily) can provide symptomatic relief but should be used with caution in patients with dysentery of unknown cause and avoided in patients with possible C difficile (those taking prophylactic antibiotics) given the risk of development of toxic megacolon. There is also some evidence, though not conclusive, that antimotility agents can prolong the duration of some enteric infections such as shigellosis. Effective antibiotic therapy reduces the duration of ETEC and EAEC, the most common causes of traveler’s diarrhea. Development of antibiotic resistance is a major problem and has reduced the efficacy of trimethoprim-sulfamethoxazole, aminopenicillins, and tetracyclines. Instead, quinolones and azithromycin are now recommended. The nonabsorbed antibiotic rifaximin is effective against ETEC and may ultimately become the empiric antibiotic treatment of choice for nondysenteric traveler’s diarrhea.

Prevention is the most effective approach to reducing the burden of travelers’ diarrhea. Patient education is a crucial component of this strategy. Travelers should be instructed not to consume water that has not been thoroughly boiled, filtered with iodine-containing filters, or chemically treated with bleach or tincture of iodine. Drinks, especially those with ice, should be avoided. Teeth should be brushed with bottled or treated water and ingestion of water while showering should be avoided. Only thoroughly cooked vegetables, fish, shellfish, and meat should be eaten. Sauces and dips such as guacamole are a frequent source of infection. Fruits, unless freshly peeled, should not be eaten. Fruit-, vegetable-, and meat-containing salads should be avoided.

Bismuth subsalicylate (two tablets or 30 mL of the liquid preparation four times daily) can be taken as prophylaxis. However, compliance is generally poor due to the inconvenience, and salicylate toxicity is a small risk especially if intake is prolonged. Antibiotic prophylaxis for the casual, healthy tourist, although often used, is not generally recommended in view of cost and the risk of inducing antibiotic resistance among pathogens. Undesirable side effects of antibiotic prophylaxis may include allergic reactions, antibiotic-induced diarrhea, C difficile colitis, and yeast infections. Antibiotic prophylaxis can be justified for individuals who are immunocompromised, who have IBD or other significant comorbidities, or for those travelers whose responsibilities and schedule are such that severe traveler’s diarrhea would be more than an inconvenience and would potentially negate the purpose of their journey. Quinolones such as ciprofloxacin (500 mg daily) are most widely used, although resistance to these agents is increasing. Rifaximin (200 mg twice daily) is promising, reducing diarrhea more than threefold among travelers to Mexico in one study with little apparent alteration of the colonic flora.

Cheng AC, Thielman NM. Update on traveler’s diarrhea. Curr Infect Dis Rep. 2002;4:70-77. [PMID: 11853660]

DuPont HL, Jiang ZD, Okhuysen PC, et al. A randomized, doubleblind, placebo-controlled trial of rifaximin to prevent travelers’ diarrhea. Ann Intern Med. 2005;142:805-812. [PMID: 15897530]

Goodgame R. Emerging causes of traveler’s diarrhea: Cryptosporidium, Cyclospora, Isospora and Microsporidia. Curr Infect Dis Rep. 2003;5:66-73. [PMID: 12525293]

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