Travelers Diarrhea

Etiology

The most common bacterial cause is enterotoxigenic Escherichia coli (ETEC), with estimates that the bacteria is responsible for nearly 30% of cases. Other common bacterial causes of travelers’ diarrhea include Campylobacter jejuni, Shigella, and Salmonella species. Norovirus is the most common viral cause while rotavirus is another source of infection. Giardia intestinalis is the most common parasitic source while Cryptosporidium and Entamoeba histolytica can also cause travelers’ diarrhea. The most common cause of travelers’ diarrhea varies by region, though the source is rarely identified in less severe cases.[4][5][6]

Traveler's diarrhea can occur in both short and long term travelers; in general, there is no immunity against future attacks. Traveler's diarrhea appears to be most common in warmer climates, in areas of poor sanitation and lack of refrigeration. In addition, the lack of safe water and taking short cuts to preparing foods are also major risk factors. In areas where food handling education is provided, rates of traveler's diarrhea are low.

Epidemiology

Estimates place the incidence of travelers’ diarrhea at 30% to 60% of travelers to resource-limited destinations. Incidence and causal agent vary by destination, with the highest incidence reported in sub-Saharan Africa. Other locations with high incidence include Latin America, the Middle East, and South Asia. Risk factors are typically related to poor hygiene in resource-limited areas. These include poor hygienic practices in food handling and preparation; lack of refrigeration due to inadequate electrical supply; and poor food storage practices. Additional modifiable risk factors include proton pump inhibitor (PPI) use, recent antibiotic use, and unsafe sexual practices. Risk factors for severe complications are pregnancy, young or old age, travelers with underlying chronic gastrointestinal diseases, or people who are immunocompromised. [7][8]

Pathophysiology

Travelers’ diarrhea is most commonly spread by fecal-oral transmission of the causative organism, typically through consumption of contaminated food or water.  The incubation period varies by causal agent, with viruses and bacteria ranging from 6 to 24 hours and intestinal parasites requiring 1 to 3 weeks before the onset of symptoms.  The pathophysiology for travelers’ diarrhea differs by a causative agent but can be split into non-inflammatory or inflammatory pathways. Non-inflammatory agents cause a decrease in the absorptive abilities of the intestinal mucosa, thereby increasing the output of the gastrointestinal (GI) tract. Inflammatory agents on the other hand cause destruction of the intestinal mucosa either through cytotoxin release or direct invasion of the mucosa. The loss of mucosa surface again results in a decrease of absorption with a resultant increase in bowel movements.[9]

History and Physical

The onset of symptoms will typically occur 1 to 2 weeks after arrival in a resource-limited destination, though travelers can develop symptoms throughout their stay or shortly after arrival. Travelers’ diarrhea is considered as three or more loose stools in 24 hours or a two-fold increase from baseline bowel habits. Diarrhea often occurs precipitously and is accompanied by abdominal cramping, fever, nausea, or vomiting. Patients should be asked about any blood in their stool, fevers, or any associated symptoms. A thorough travel history should be obtained including timeline and itinerary, diet and water consumption at their destination, illnesses in other travelers, and possible sexual exposures.

In most self-limited cases physical examination will show mild diffuse abdominal tender to palpation. Providers should assess for dehydration through skin turgor and capillary refill.  In more severe cases patients may have severe abdominal pain, high fever, and evidence of hypovolemia (tachycardia, hypotension).

Evaluation

Laboratory investigation is typically not required in most cases.  In patients with concerning features, such as with high fever, hematochezia, or tenesmus, stool studies can be obtained. Typical stool studies include stool culture, fecal leukocytes, and lactoferrin. The stool should be assessed for ova and parasites in patients with longer duration of symptoms. New multiplex polymerase chain reaction (PCR) screens are becoming available and provide quick analysis of multiple stool pathogens. These screens, however, are expensive, are not widely available, and may not change the clinical management of patients.[4]

Radiological studies are not required in most cases. Kidneys, ureters, and bladder x-ray can be obtained to assess for acute intra-abdominal pathology or look for evidence of perforation in severe cases. An abdominal CT can also be used to assess for intraabdominal pathology in severe cases.

Treatment / Management

Travelers should be counseled on risk reduction before travel, including avoiding tap water & ice, frequent hand washing, avoiding leafy vegetables or fruit that isn’t peeled, and avoiding street food. Bismuth subsalicylate (two tabs 4 times a day) can be used for prophylaxis and can reduce the incidence of travelers’ diarrhea by almost half, though it should be avoided in children and pregnant women due salicylate side effects. In short high-stakes travel, it may be reasonable to start antibiotics as prophylaxis but is generally avoided in longer-term travel. Rifaximin is a commonly used chemoprophylaxis due to its minimal absorption and minimal side effects.[10][11][12](B3)

The foundation of diarrhea management is fluid repletion. In mild cases, travelers should focus on increasing water intake. Water is usually sufficient though sports drinks and other electrolyte fluids can be used. Pedialyte can be used for pediatric patients. Milk and juices should be avoided as this can worsen diarrhea. In more severe cases, oral rehydration salt can be used to ensure rehydration with adequate electrolyte repletion. In cases of severe dehydration, IV fluids may ultimately be required.

Treatment is supportive in mild-moderate cases. In patients without signs of inflammatory diarrhea, loperamide can be used for symptomatic relief.  The typical dose for adults is 4 mg initially with 2 mg after each subsequent loose stool, not to exceed 16 mg total in a day.

Also, travelers can be given antibiotics to take as needed at the onset of symptoms. Ciprofloxacin is commonly used for treatment, though there are concerns with resistance with Campylobacter species.  For this reason, fluoroquinolones are not often prescribed for travelers to Asia and azithromycin preferable. Also, azithromycin is often prescribed for pregnant travelers and children. A common regimen is 500 mg daily for three days, though evidence suggests that a single dose of 1000 mg may be slightly more effective. Parents can be given azithromycin powder with instructions to mix with water when needed. Rifaximin is a minimally absorbed antibiotic that is also available and is safe for older children and pregnant travelers.

Differential Diagnosis

• Pseudomembranous colitis
• Ischemic colitis
• Vipoma
• Radiation-induced colitis
• Food poisoning

Staging

New Guidelines for Traveler's Diarrhea

1. Travelers should be advised against the use of prophylactic antibiotics
2. In high-risk groups, one may consider antibiotic prophylaxis
3. Bismuth subsalicylate can be considered in any traveler.
4. The antibiotic of choice is rifaximin
5. Fluoroquinolones should not be used as prophylaxis

Prognosis

The outcomes in most patients with traveler's diarrhea are good. However, in severe cases, dehydration can occur requiring admission.

Complications

• Dehydration
• Malabsorption
• Sepsis
• Hemolytic uremic syndrome
• Reactive arthritides