Wednesday, June 4, 2008

Dietary Hygiene in the Prevention of Travellers' Diarrhea

This information is intended to be educational in nature and should not be construed as medical advice. You should consult your physician regarding any specific medical conditions or questions and before taking any medications.

Travellers' diarrhea is the most common illness experienced by travellers from industrialized countries journeying to Third World countries. While it is usually a self-limiting illness, it can nevertheless ruin three to four days of a holiday or require alteration of holiday plans. The primary cause of travellers' diarrhea is infectious. The etiology is both geographically and seasonally dependent, but the principle agents include enterotoxigenic Escherichia coli, Shigella and Salmonella species, Campylobacter jejuni, non-cholera Vibrio species, Plesiomonas shigelloides, Aeromonas species, Giardia lamblia, Entamoeba histolytica, Cryptosporidium parvum, rotavirus, and Norwalk virus. Travellers' diarrhea is strikingly common, with an incidence estimated from 20% to over 80%.

It is common for travellers to have profound changes in their bowel habits due to many factors, not least among them dietary changes. We do not consider loose movements to be diarrhea, but rather limit the definition to:

Travellers' diarrhea

The occurrence of three or more unformed stools within a 24 hour period or any number of such unformed stools when accompanied by either nausea, vomiting, abdominal cramps, tenesmus (involuntary straining with little or no passage of fecal matter), or fever.

As is the case for other enteric infections, ingestion of contaminated food and water is thought to be the most important means of transmission of travellers' diarrhea. This is the basis for stressing the importance of dietary hygiene to travellers. Although there have been many studies examining the causes of travellers' diarrhea and its treatment, there is no consensus among the few studies which have addressed the question of whether following food and water precautions will reduce the likelihood of acquiring travellers' diarrhea. Until further knowledge is available in this area, we advocate a common-sense approach to avoiding these enteric infections: limit potential exposure by choosing what goes in your mouth, and wash your hands before you eat.

We recommend avoiding the following foods that are generally considered high-risk:

-Drinking untreated water (this includes brushing your teeth with it!)

-Ice cubes in a drink (alcohol does NOT provide protection)

-Chang (rice beer, usually made with untreated water)

-Raw vegetables


-Uncooked fish

-Uncooked or rare-cooked meat

-Unpeeled fruit

-Fresh fruit juice


-Ice cream

-Any kind of street vendor food

And the following foods in Kathmandu that have specifically been found to have a high association with subsequent diarrhea:

-Lassi (a yogurt shake)




Except in certain special cases I do not support the use of antibiotic prophylaxis against diarrhea. There is a protocol involving taking Bismuth Subsalicylate (Pepto-Bismol®), two tablets four times per day, which has been shown to be at least partially protective against travellers' diarrhea. However, the volume of tablets that would need to be carried make this impractical for most trekkers. This medication is also not without side effects - it may transiently color your tongue and your stools black, it can cause constipation, and it is a salicylate (related to aspirin) so it should be taken only with caution by persons on anti-coagulants or allergic to aspirin.

Treatment Issues

Travellers' diarrhea is felt to be a self-limiting illness, it will usually resolve on its own. However, most trekkers are on a limited vacation and don't want to spend a week of it running a relay between their bed and the outhouse, so treatment with antibiotics is often seen as a better alternative.

In all cases, careful attention must be paid to adequate rehydration. This is particularly important at altitude, as we believe dehydration may be a risk factor for developing altitude sickness. In cases of profound fluid loss an electrolyte replacement solution is preferable to plain water. Various commercial solutions and powder mixes are available in Kathmandu, or a homemade variety may be used:

World Heath Organization/UNICEF Oral Rehydration Fluid

1 liter water (obviously, this should be disinfected)

10 g (2 teaspoons) sugar

2.5 g (1/2 teaspoon) salt

2.5 g (1/2 teaspoon) baking soda (sodium bicarbonate)

Antibiotic treatment varies depending on the cause of the diarrhea. Unfortunately, when trekking in the mountains there is rarely a medical lab handy, and an empiric diagnosis may be the only choice. Travellers' diarrhea generally falls into two main groups: presumed bacterial and presumed protozoal (Giardia). Amoebic dysentery is rare in trekkers; Cyclospora ("blue-green algae") is only seen during the monsoon (summer) months, and thus rarely in trekkers; there are no specific treatments for the viruses.

Bacterial Diarrhea

Bacteria are by far the most frequent cause of travellers' diarrhea in Nepal, and are responsible for 70 - 80% of cases. Enterotoxigenic Escherichia coli is the chief cause, followed by Shigella. In general, bacterial diarrhea is characterized by a sudden onset of "explosive" watery diarrhea, plus or minus any of: fever, nausea, or blood in the stool. The onset is from one to seven days after exposure, and is usually so dramatic that patients can tell us just when they got sick. I can recall no better description of this syndrome than that given by B.H. Kean (1):

At 4 AM he awakened with a start, desperately aware that he was about to move his bowels. He traversed the bed-to-bathroom distance in what must have been record time, and relieved himself of a totally watery bowel movement which was accompanied by slight "transverse colon" cramps. The patient returned to bed in a stunned state, only to discover that no sooner had he arrived than he was constrained to leave again, with uncustomary alacrity. This stacatto ballet continued at 15-minute intervals with the patient exhibiting progressive weakness, profound malaise, increasingly severe cramps, almost constant nausea, and several episodes of vomiting.

The preferred treatment for bacterial diarrhea in Nepal is one of the fluoroquinolone antibiotics:

-Norfloxacin 400 mg twice a day for three days

-Ciprofloxacin 500 mg twice a day for three days

-Ofloxacin 400 mg twice a day for three days

None of these should be given to children; pregnant women should discuss with their physician the risks-versus-benefits of taking any of these medications. It is common for patients to report dramatic improvement after their first dose of antibiotics.

Sulfamethoxasole-trimethoprim antibiotics (SMX-TMP, Co-trimoxasole, Septra®, Bactrim® and others) are often ineffective against bacterial diarrhea in Nepal due to relatively high resistance there among the bacteria that cause this illnesses. These medications are however, first-line treatment for cyclospora ("blue-green algae").

Protozoal Diarrhea: Giardiasis

Giardia lamblia is a one-celled parasite that causes diarrhea and gastrointestinal upset. It has a much longer incubation time than the bacterial diarrheas, with onset of symptoms ten to fourteen days after ingestion. The diarrhea is much more indolent, without the explosive onset, more on-again off-again in nature. There may be a fever, but it is less common than with bacterial diarrhea. There may be nausea. The famous "rotten egg burps" are not diagnostic: they occur with equal frequency in bacterial diarrhea (as well as from other causes). The preferred treatment for Giardia is one of the nitroimidazole antibiotics:

-Tinidazole 2 grams at bedtime for two nights (not available in the US)

-Metronidazole 500 mg three times a day for seven days

Common side effects of these medications include nausea, a bitter taste, and the possibility of a violent interaction with alcohol. DO NOT DRINK ALCOHOL while on these medications or for several days afterwards!

Anti-motility drugs

There are several anti-motility medications that many trekkers carry and use against diarrhea, often with the mistaken impression that they are antibiotics. These medications slow down the movement of the gut (thus slowing the diarrhea) but do not treat the infection. They are useful to treat cramping. I discourage their use except in combined use with appropriate antibiotics. This class of medications includes:

-Diphenoxylate (Lomotil®)

-Loperamide (Immodium®)

-Codeine and other narcotics

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