CIWEC Clinic Travel Medicine Center treats approximately 2000 people with traveler`s diarrhea each year. Through our clinical experience and the research we have published, we have gained considerable experience in understanding the concerns that travelers have in avoiding sickness, and what to do if they should fall ill. Questions about symptoms, stool exams, fluids, diet, antibiotics, symptomatic medications, and so forth, are posed daily in our clinic. We have found many of the answers from our own experience, through the research we have performed, and through the research that others have done around the world. What follows is an attempt to share with you answers to the most commonly asked questions about diarrhea in travelers. It is my hope that this article will help you avoid illness where possible, to be able to self-diagnose and treat your own cases of diarrhea when you are away from medical car to seek help as appropriate, when you need it.

Introduction What is diarrhea? Why do travelers get diarrhea? What is organisms that cause diarrhea? What is the normal situation in the human intestine? How do the organisms cause diarrhea? How do we determine the cause traveler`s diarrhea in an individual case? What is stool examintaion? How can diarrhea be avoided? Do people become immune to traveler`s diarrhea? How do your treat traveler`s diarrhea? Does diet have an effect on traveler`s diarrhea? Water purification and personal hygiene Is it `bad` ta take antibiotics to treat diarrhea? A guide to self-treatment Diarrhea in Children Traveler`s Diarrhea while Pregnant or Nursing Other causes of traveler`s diarrhea Tropical sprue Returning home with diarrhea Research into traveler`s diarrhea: the future

Introduction

Diarrhea is a difficult topic to get people to take seriously in the developed world. However, as people contemplate a trip to an underdeveloped area of the world, they become increasingly anxious about the possibility of getting diarrhea while traveling. Some people don`t travel at all to such destinations because of their fear of diarrhea or other illness. Most traveler`s health books take a casual attitude towards traveler`s diarrhea, giving pet names for the illness itself ("Delhi Belly", "Kathmandu Quickstep"), and repeating several eating rules which are usually condensed to "boil it, peel it, or forget it." This attitude can lead the traveler to believe that diarrhea is a risk that only happens to careless people.

The reality of diarrhea in travelers is in fact much different. There has been much research detailing the types of organisms that can cause diarrhea, but very little research into how the organisms are acquired during travel. You can sometimes get ill despite your best efforts to avoid it. It then becomes useful to know how to diagnose and treat the various organisms that can be the cause of traveler`s diarrhea. Diarrhea in travelers is essentially never fatal, although it can be immensely uncomfortable at times. From a minor nuisance to a major cause of pain and hopelessness, diarrhea can have a major effect on the enjoyment and schedule of one`s journey.

What is diarrhea?

Diarrhea is a term that is used to describe stools that are more liquid and frequent than normal. There is no absolute definition of what constitutes diarrhea, but various definitions are utilized for the purpose of research, such as "3 or more unformed stools within 24 hours." Funk and Wagnell`s dictionary defines diarrhea as "morbidly frequent and fluid evacuation of the bowel," which has a more poetic ring to it. The word diarrhea is derived from the Greek and means "to flow through."

Dysentery is a term used for diarrhea when there is evidence that the organisms are invading the intestinal wall, causing pus, mucus, and blood to appear in the stool. There is often fever and abdominal cramps as well. Again, the word is derived from the Greek, and means "bad intestine" (there must have been a lot of diarrhea in Greece in the old days). Although the term dysentery conjures up more emotion, there is no clear-cut border between diarrhea and dysentery, and treatments are often the same. There is too much emphasis on trying to define the difference between diarrhea and dysentery in travel advice books. If you are having frequent loose bowel movements, and this is a change from your normal pattern, you can call it diarrhea.

Diarrhea in travelers is almost always caused by ingesting various infectious microorganisms that have the capacity to cause frequent unformed stools. However, diarrhea can have many other causes, such as nervousness, alcohol, surgery, use of various medications, or as a symptom of an underlying illness. Back home in developed countries, the chances of acquiring an infectious diarrhea are so small that when patients come in with diarrhea as a symptom, we usually look for some of these other causes first. When we travel, though, the exposure to infectious organisms is so high in comparison to back home, that we almost always look for an infection first.

In my experience with travelers, no one seems to have trouble deciding if they have diarrhea or not. They seem to adopt the attitude of an American Supreme Court Justice who, in referring to obscenity, said, "I don`t know how to define it, but I know it when I see it."

Why do travelers get diarrhea?

One of the triumphs of modern public health in the developed world is that we have managed to keep our stool out of our water supplies and the general environment. The organisms that cause diarrhea in travelers are the same organisms available throughout the world. The reason that we get diarrhea when we travel to certain developing countries is that stool is more generally available in the environment: in drinking water, on the street, on people`s hands, on flies, and on the food itself. The only way you can get a diarrheal illness is to eat organisms that have grown in someone else`s intestines: in other words, you have to eat someone else`s stool. Now, most sane people would not consciously eat someone else`s stool, but with the substance strewn widely in the environment, it is harder than you might think to avoid doing so.

Imagine a fancy hotel in Kathmandu. The high wall topped with broken-glass just behind the hotel makes a convenient shield for local people who don`t have toilets in their homes to sneak out for their daily evacuation. If they themselves have diarrhea, as they frequently do, their trips may be more numerous. The wall forms one side of a narrow path, down which some of the hotel kitchen employees come on their way to work. The odor from the "outdoor toilet" attracts numerous flies who lay eggs in the stool. Then, hungry, they are attracted to the odors emanating from the hotel. Their feet covered in stool, like those of the hotel employees who walked down the path, they also head for the kitchen.

In the kitchen, flies move freely about. The work surfaces are soon covered with raw meat, most of which is covered with bacteria present within the animals when they died. When they are finished cutting up the meat, they move to the vegetables, often on the same surface, not recognizing the danger. One of the employees has diarrhea himself, and has to make frequent trips to the toilet, where he cleans himself without toilet paper. By now, the kitchen workers hands are covered with organisms from the raw meat, from themselves, and from their shoes. They finish cooking the lasagnas and quiches for the day, testing their cooling temperatures with an expert (but unfortunately heavily contaminated) finger, inoculating a few thousand bacteria onto the surface, which is now around body temperature (optimum growing temperature for the bacteria). The bacteria grow the rest of the morning and on into the afternoon, dividing regularly and doubling every twenty minutes. By dinner time, the area of inoculation is still completely microscopic in size, but contains more than a billion bacteria. The lasagna is sliced, and heated slightly, but not enough to kill the bacteria. Like a game of Russian roulette, one of the diners will get the infected piece.

The traveler who ordered the lasagna takes care to not drink the water that is served along with his meal. He eschews ice in his drink, and refrains from eating the green salad which is served with the meal. He will go to sleep feeling comfortably satiated and confident, only to be awakened at 3:30 a.m. with the urge to vomit, followed rapidly by profound diarrhea. The rest of the night passes in a repetitive haze of cramps, vomiting, and diarrhea. And all the time the hapless traveler thinks, "But I followed all the rules."

What are the organisms that cause diarrhea?

Thirty years ago the exact cause of traveler`s diarrhea was still, for the most part, unknown. Most of the time when travelers with diarrhea were studied, a specific organism that was known to cause diarrhea could not be found. Technical advances in isolating organisms that can cause disease (called "pathogenic" organisms) have filled in most of the gaps in our knowledge. Still, a study of diarrhea in travelers is considered to be a good study if even 60% of the people studied have a known pathogenic organism in their stools (at the CIWEC Clinic in Kathmandu, we had 80% positive findings). This means that there are likely even more causes of diarrhea yet to be discovered. In fact, at the CIWEC Clinic, we discovered a new cause of diarrhea in 1989, that came to be called Cyclospora.

One of the major breakthroughs in understanding the causes of traveler`s diarrhea was isolating a particular kind of bacteria called Enterotoxigenic Escherischii coli, or ETEC. This is a bacteria that looks identical to the E coli organisms that are one of the major normal inhabitants of the bowel. Only elaborate additional testing found out that these particular bacteria could produce a toxin that was similar to the toxin of cholera bacteria. The toxin binds to intestinal cells, causing them to produce water into the intestine, which causes diarrhea. In all subsequent studies, ETEC has usually been the most common bacterial pathogen found in patients with traveler`s diarrhea, accounting for 25% to 60% of cases.

In addition to ETEC, there are about a dozen other bacteria that can cause diarrhea in travelers. The most common of these organisms are called Shigella, Salmonella, and Campylobacter. Certain other bacteria can cause diarrhea, not through infection, but by growing on the food and producing a toxin, which results in a violent syndrome we call "food poisoning." Besides the bacteria, there are several protozoa that can cause diarrheal disease. Protozoa are larger organisms, often called "single-celled animals." These organisms have names such as Giardia lamblia, Entamoeba histolytica, Cryptosporidium jejuni, and Cyclospora cayetanensis. They are much less common as a cause of infection in travelers than bacteria. We will discuss each of them under their own heading.

Finally, there is the relatively recent discovery of intestinal viruses that can cause diarrhea. Viruses are particles that are so small that for centuries after the microscope was invented, they couldn`t even be imagined. Finally, with sophisticated antibody testing, and the use of the electron microscope, we have a good understanding of these strange organisms. Because these organisms don`t have a life outside the cells they have invaded, it has been very difficult to invent antibiotics that can treat them without also killing their host cell. Fortunately, the human body can identify the invaders and produce antibodies that stick to the virus particles, marking them for pick-up by the scavenging immune cells in the blood. Within a few days the infection is usually under control.

The intestinal viruses have descriptive names based on their shape, such as rotavirus and astrovirus. Viruses currently account for about 10% of the causes of traveler`s diarrhea. But it`s possible that some of the explanation for the missing 20-40% of specific causes of diarrhea in travelers may be filled in by viruses yet to be discovered.

What is the normal situation in the human intestine?

To understand how pathogenic organisms can overcome our defenses and cause diarrhea, we have to understand the normal structure and functioning of our intestines. The gastrointestinal tract is one long tube, starting at the mouth and ending in the anus. After food is chewed in the mouth, it drops straight to the stomach, where it is met by a highly acidic environment that can kill most microorganisms. The food then moves to the small intestine, where it is mixed with enzymes and other digestive aids, and absorbed into the body. Most of the small intestine is free of bacteria, but as it approaches the large intestine, we begin to see some of the trillions of normal bacteria that live in the gut. The small intestine is devoted to absorption of food, and the large intestine is devoted to producing formed stool for evacuation. In the normal situation, the large intestine begins to recover some of the liquid in the food (that we now start to call "stool"), and as the stool makes its final turn and heads south, it begins to have some solid qualities. In the absence of diarrhea, we usually evacuate the last portion of our large intestine once or twice a day.

The food--destined to become stool--is moved along the intestine by rhythmic, wave-like contractions called peristalsis (from the Greek: "around compression"). These contractions flow one after the other, every 6-10 seconds, gently pushing along the food, liquid, and air in the intestines. The peristalsis is controlled by what is called the "autonomic" nervous system, which means that it works without our conscious control. This nervous system is, however, subject to emotions, and stress, and may react to various noxious stimuli (such as infection or toxins) in the gut. An increase in peristalsis will result in more frequent and liquid stools, as there will not be enough time to absorb the food and liquid out of the intestine. A decrease in peristalsis or absence of peristalsis may result in no bowel movements at all, or may contribute to a build up of gas (that would ordinarily be milked gently along the intestine). Sometimes, after an episode of infectious diarrhea, peristalsis may be disturbed for awhile, with some sections of the intestine contracting normally, and others not moving at all. The non-moving sections act as a kind of obstruction to the air trying to move through, and this can cause uncomfortable gas and cramps. Within a few days, when normal rhythm is re-established, this uncomfortable feeling disappears.

The bacteria in the intestine can be roughly divided into those that need oxygen to survive, and those that can`t grow in the presence of oxygen. Most diarrhea are caused by oxygen-requiring (aerobic) organisms. However, the bulk of the bacteria in the gut are non-oxygen requiring (anaerobic) organisms. The antibiotics with which we treat diarrhea affect only the aerobic bacteria, for the most part. Both types of bacteria can grow rapidly in the ideal internal conditions of the human intestine, doubling every twenty minutes until limitations of nutrients and space slow them down. Even after antibiotic use, the remaining bacteria can restore themselves to normal in a number of days.

Stool itself is composed of undigested bits of food, and trillions of bacteria. The liver filters broken-down red cells out of the blood and excretes the red cell pigment through the common bile duct into the intestine. This substance, called bilirubin, gives stool its characteristic dark brown color.

How do the organisms cause diarrhea?

The organisms that cause diarrhea have to make a living like any other living organism. The various organisms have solved the problem in different ways. First, they have to find a way to survive in the external environment, outside of the intestine, long enough to find a new host. The bacteria prefer a moist environment and warm temperatures, but some of them can withstand harsh conditions, including drying out for a period of time. The protozoa can`t function in the external environment. They travel outside the gut in a space capsule-like configuration called a "cyst." The cysts can withstand extremes of conditions that would rapidly kill the active form of the protozoa (which is referred to as a "trophozoite"). Viruses are inactive outside of the human cell, whether they are in the intestine or not.

To successfully infect a host, the organisms have to get past the intimidating barrier formed by one`s stomach acid. A stomach contains a potent form of hydrochloric acid, and this can kill most bacteria. Some, however, are more resistant than others. Shigella, which causes a rather severe form of diarrhea, can induce an infection in volunteers who swallow as few as ten organisms. ETEC, on the other hand, has to send in at least one billion organisms to have a crack at getting enough through to cause an infection. The protozoal cysts are relatively acid-resistant, and small numbers (10-100) have caused infections in volunteers.

Some of the organisms infect the small bowel (Salmonella, ETEC, Campylobacter, and Giardia), while others prefer the large bowel (Shigella, Entamoeba histolytica). Although toxins have been identified for several organisms (ETEC and Shigella), the exact way that the other organisms cause diarrhea is not known. They may produce toxins that haven`t been identified, or they may produce inflammation through direct invasion, or it may be a combination of these mechanisms. Some of these pathogenic organisms can infect some individuals without causing symptoms, and we don`t know why this occurs. Subtle differences in the organisms themselves, or factors that make some people more resistant, may explain why some people are more affected than others by their presence. What is clear, however, is that the organisms themselves and the toxins they produce cause the diarrhea. Diarrhea is not a defense mechanism by the host to try to "wash out" the disease-causing organisms.

How do we determine the cause of traveler`s diarrhea in an individual case?

When a traveler is suffering from diarrhea, the chances are that their life is being disrupted in some way. This disruption may range from severe pain and dehydration down to the relatively minor inconvenience of having to find a toilet in a rush. Some journeys may be almost impossible to accomplish with uncontrolled diarrhea, such as a prolonged Asian bus ride. The sum total of these disruptions and inconveniences can be summed up as follows: People with diarrhea don`t want to have diarrhea.

Knowing that there are many causes of traveler`s diarrhea can intimidate a traveler when they need to diagnose and treat their own case of diarrhea. Even doctors who are inexperienced in treating traveler`s diarrhea may not have a clear approach to the problem, and may be over concerned about making a specific diagnosis before treatment. The best way to make a diagnosis in someone with traveler`s diarrhea is to take a history of the illness from the patient, do a brief physical examination, and do a stool exam (if available from a reliable lab). In many cases, the diagnosis can be surmised from the history alone.

The history is the single most useful tool in determining the probable cause of a case of traveler`s diarrhea. The travel history is the place to begin. I often start my consultation with travelers in my clinic by asking, "How long have you been traveling in Asia?" The longer they have been traveling, the more likely they are to have been exposed to all the diffent causes of diarrhea. If they arrived in Nepal the night before, it limits the organisms that you need to be concerned about. A basic rule of thumb is that bacteria and viruses that can cause diarrhea have an incubation period of a few hours up to two or three days at the most. Protozoa, such as Giardia and E histolytica, have an incubation period of seven to 14 days. Food poisoning generally occurs within two to eight hours after eating the toxin. Thus, the travel history can help you rule out possible causes of diarrhea without even doing a stool exam.

The history of the present illness is the crux of the matter. Understanding exactly how and when the illness began and how it progressed will generally give you a much clearer picture of the possible cause of diarrhea. I usually ask the question, "What exactly happened when your illness began?"

Bacterial diarrheas invariably have an abrupt onset. That means that the patient can generally tell you the exact time of day that they began to feel ill. Often, the illness begins in the middle of the night, or in the early morning. You are rushed from the bed by sudden cramps and the urge to defecate, and the result is a very runny or frankly liquid stool. As soon as you get back to bed, you have to run again. Bacterial diarrhea can be accompanied by nausea, vomiting, and fever, but the diarrhea can occur all by itself. The general concept is the abrupt onset of relatively uncomfortable diarrhea.

In contrast, the protozoal diarrheas, mainly Giardia and E histolytica, have a more gradual start of less severe symptoms. With Giardia, you may start the day with a couple of loose bowel motions, only to feel generally okay the rest of the day. That evening you might have one or two more loose stools, but you sleep through the night, only to start the cycle the next day. After a few days, you might be more aware of a generally grumbly feeling in your intestines, increased gas, and a growing sense of fatigue. Many patients with Giardia tolerate their symptoms for two weeks or more before coming to the doctor. The general hallmark is the gradual onset of a less severe diarrhea that is generally the same day after day.

Although many travelers fear the term "amoebic dysentery," in fact this form of diarrhea is extremely rare in Nepal. Infection with the amoeba called "E histolytica" occurs in about 1% of the patients who come to CIWEC Clinic with diarrhea. However, almost all of these infections present as a chronic, low-grade diarrhea that alternates every 1-3 days. The patient experiences diarrhea for a day or so, then no diarrhea for a day or so, and then diarrhea again. Gradually they experience weight loss and fatigue, and come to the doctor after being sick for a month or more. Amoebic dysentery is a severe form of amoebic infection that causes severe crampy diarrhea with multiple small bowel movements, often with blood. This form is so rare that we see only about one person per year with this form of amoebic infection. However, local laboratories around the world often overdiagnose "amoebic dysentery" (that is, they say it is there when it is not). Almost always, when travelers are told by local doctors or laboratories that they have "amoebic dysentery" they actually have bacterial dysentery, and the lab test was simply wrong.

Occasionally, travelers get the feeling that they are infected with some organism that simply won`t go away. After an initial bout of diarrhea, they feel well for a week or two, and then come down with some form of diarrhea again. After a few episodes, they begin to think that all these episodes are related, and they come to our clinic complaining of "six weeks of diarrhea." When we actually question the person, we find that she had 3 days of diarrhea and fever in Delhi, six weeks earlier. She took medicine and felt quite well, but her stools remained looser than normal, and slightly more frequent. Two weeks later she had vomiting for one night. Her stools gradually improved, but she had the occasional urgent bowel movement at an inconvenient time. Ten days later she had 4-5 bowel movements per day, for two days, which cleared up by itself. Then she was completely well until she flew to Nepal, where she developed diarrhea suddenly on her second night, going 10 times during the night, until arriving at our clinic the following morning. The patient thinks that the same organism has been inside since Delhi, flaring up at times, and now, having gotten much worse in the last day, she is seeking help.

Our understanding of her illness is quite different. We would say that she had an acute bacterial diarrhea in Delhi, which resolved. After an acute illness, the bowels may stay irritated for a period of time, preventing normal formed stools, but not really associated with any bad feeling. Then she probably had an unrelated food poisoning, which accounted for her vomiting--without diarrhea--two weeks later. This was followed by another bout of acute diarrhea, either bacterial or viral, which resolved by itself. She was then well until a new illness the night before she came to the clinic. So all we have to do is figure out the cause of her symptoms for the last 12 hours; she hasn`t really had "diarrhea for 6 weeks." A simple rule of thumb is that if there are six days or more between bouts of diarrhea, the second bout is unrelated to the first.

What is a stool examination?

Stool is composed of bits of undigested food, bacteria, and the pigment from broken down red blood cells. It can be either formed, soft, or liquid. To collect stool for examination, a clean container should be held below the anus, and the stool should be defecated straight into the container. Don`t try to collect stool that has already landed in the toilet water. If you are collecting stool from an infant in diapers, scrape the stool out of the diapers as soon as you detect it; otherwise it can dry out and be unusable. Although it seems distasteful to handle stool in this fashion, particularly when you are back in your home country, you`ll find that submitting stool samples can be a relatively normal part of expatriate and travel life.

Stool is examined in different ways in different laboratories, but the general method is as follows: The stool is first examined grossly for blood or mucus. Its consistency is noted. Then a small smear of stool is placed on a glass slide, and diluted if necessary to make it easier to see. A second, larger portion of stool (about the size of a large pea) is mixed with chemicals, and then centrifuged at high speed for several minutes. The chemicals dissolve some of the undigested bits of food, and the centrifugation concentrates the parasites at the bottom of the tube, making them easier to detect when spread out on a slide. In almost all local laboratories in the developing world, the concentration process is not done, reducing the chances of finding some parasites. In many labs in the United States, only one smear is made, but it is stained with a special stain (the trichrome stain) that makes parasites easier to see.

Under the microscope the stool appears as thousands of small irregular shapes. It takes quite an experienced eye to pick out the significant shapes against this cluttered background. It is a bit like trying to pick out a maple leaf on a lawn full of oak leaves. Once a suspicious shape is detected, the technician goes to a higher power to try to make a specific identification. This process takes a lot of training, patience, and dedication. One is looking for tiny differences between clear objects with indistinct internal structures. Making definitive identification is like being a bird watcher who is interested in small nondescript brown birds. It is easy to tell an eagle from a sparrow, but it is much harder to differentiate between the different sparrows that you see. However, making this distinction is critical in deciding whether the organism you are seeing could be the cause of the patient`s diarrhea.

The most important concept to learn about stool exams is that although they can be quite specific in good hands, it is not a very sensitive exam. What this means is that if you find something, you can be quite sure of what it is, but if you don`t find something, it doesn`t mean that there is nothing causing diarrhea. Organisms such as Giardia and E histolytica don`t always show up in the stool, even it they are causing an infection. When they did daily stool exams on people that they knew were infected with these organisms, they could only find them every fourth or fifth day. On the other days, the stools were interpreted as "negative." So, the important point for travelers is that a stool exam is not an overall screening test to determine if you have something that needs to be treated. When a pathogen is found in a reliable lab, you can have confidence in the finding, but when the report comes back "negative" it doesn`t necessarily mean that you have nothing to worry about. This is the single biggest cause of confusion in our clinic.

The stool exam can add to our knowledge about the patient`s diarrhea in several ways. First, the technician looks for the presence of white blood cells or red blood cells, which can be indirect signs of bacterial infection (such as Shigella). Although the technician will see millions of bacteria, there is no way to tell the harmful bacteria from the normal bacteria under the microscope. If white cells are present, however, it is a convincing sign that the patient has a bacterial diarrhea. The complicating factor is that many people can have a bacterial-caused diarrhea without having white cells in the stool.

The main organisms that the technician is concerned with are the protozoa: Giardia, Entamoeba histolytica, Cyclospora, and Cryptosporidium. These organisms need to be first discovered (which involves patiently scanning dozens of microscope fields), and then correctly identified, distinguishing from numbers of other protozoa that have been identified in the human intestine, but are not thought to be the cause of diarrhea. These harmless organisms have names such as Entamoeba coli, Endolimax nana, Blastocystis hominis, Iodamoeba butschlii, and Trichomonas. There is also a kind of large white blood cell, called a macrophage, which can be easily mistaken for an amoeba.

Amoebas can exist in two forms: as an active trophozoite, which looks like a plastic bag loosely filled with water, with no distinct internal structures; or as a cyst, which has more rigid walls, and distinct internal structures. The amoebas can only be distinguished from each other when seen in the cyst phase. By carefully measuring the size and counting the nuclei, the various amoebas can be identified. A careless or lazy lab technician could just label them all Entamoeba histolytica, leading to wrong or unnecessary treatment, without improving the diarrhea.

Worm eggs are much larger than protozoa, and generally easy to spot. However, unusual worms, perhaps picked up in another country, or with specific associations (such as eating undercooked fish), can be difficult to identify. Eating a worm egg begins a developmental life cycle that can take more than 7 weeks to achieve an adult worm. So worms are unlikely to be detected in the first two months of travel. Overall, worms are picked up by only a handful of travelers (about 5%).

The difficulty of performing a good stool exam leads to many errors being made by local laboratories in developing countries. Although one might assume that the high rate of positive findings and the constant experience that local technicians might have would be an advantage, they often have poor quality microscopes and inadequate training and motivation to do the job correctly. It is partly for this reason that it makes more sense to focus on the clinical history, and what seems to be the likely cause of the diarrhea, rather than relying entirely on a stool exam in a developing country.

In recent years, test kits have been devised to detect specific pathogens in the stool without looking through the microscope. These tests rely on reactions between the organism and antibodies in the test kit. Although these tests can be performed by less skilled personnel, they have not been fully tested against highly competent lab technicians under real-life conditions. So we don`t know if they truly increase the rate of diagnosis or not. They seem to be quite accurate, however, so a positive test for a specific organism can usually be trusted. Test kits currently exist for Giardia and Cryptosporidium.

How can diarrhea be avoided?

Depending on the hygiene practiced in the country you are visiting, it may be impossible to avoid getting diarrhea if you stay long enough. We have also shown that the time of year that you visit may make a big difference in your risk of getting sick with diarrhea. In Nepal, flies begin to appear in large numbers at the end of March, and are present until the heaviest rains of the monsoon begin in July. These months correspond with a greatly increased risk of diarrhea risk compared to the rest of the year.

The best way to avoid getting diarrhea is to be conscious of how you can avoid eating or drinking substances that may be contaminated with stool. The reason that the advice "boil it, peel it, or forget it" is basically sound (although not sufficient), is that water is considered to be contaminated in most developing countries, and boiling disinfects it completely. Many vegetables and fruits become contaminated on their surfaces, either in the fields or in transit to market. The insides stay clean, and can be eaten safely after the peelings are removed. However, the lack of cleanliness practiced in the kitchen of the restaurant at which you may eat is something that may not be obvious, and over which you have no control. A few other ordering tips may help prevent some cases of diarrhea:

Sufficient heat destroys all microorganisms and their toxins. Any food item which is thoroughly cooked or heated throughout, and is served while still quite hot, should be safe to eat. Water served at hotels and restaurants may not have been boiled, and should be avoided. Ice is often made from untreated water, and freezing does not kill the organisms that can cause diarrhea. Bottled water may not be safe, as there are no quality standards in the countries in which they are produced. Carbonated soft drinks are safe because the carbonation lowers the pH of the drink (making it acidic), and this acidic environment kills all the bacteria. Beer would likewise be a safe choice. Stronger alcoholic beverages would be safe in themselves, but a shot of whiskey in a glass of water will not make the water safe to drink.

In Nepal, many restaurants offer fresh salads that they claim have been soaked in iodine. This technique is effective, if carefully performed every time. One of the hazards of tourist restaurants is that their owners may have good intentions, and lay down good rules, but the overworked kitchen staff may take shortcuts at times. Raw or undercooked meat can also be contaminated and should definitely not be eaten in a developing country.

A study that we published in 1996 provided evidence that foods that are cooked once during the day, and then sliced and served later, such as quiche and lasagna, were high risk for diarrhea. Blended fruit and yoghurt drinks, known locally as "lassis," were also high risk for diarrhea.

You can begin to see why even the most careful traveler can get sick occasionally in certain countries. From a scientific point of view, there have not been any conclusive studies done on travelers which support the various rules for staying well while traveling. One study found that following the rules did seem to make a difference in the first few days of travel; another study found that people who thought they were the most careful had more episodes of diarrhea than people who were less apt to follow the rules. The lack of supporting studies reflects the difficulty of performing such research rather than the lack of efficacy of the rules. In addition, researchers have not been able to establish with any certainty exactly where travelers get sick in most cases. Was it the food from the street vendor, the ice cream from the shop, the dinner from the hotel, or the dirty glass in the tea shop? No one knows.

The CIWEC Clinic studied 77 people who had recently arrived to live in Nepal during a one year period. The group average 3.2 episodes of diarrhea per person per year. This rate of diarrhea is identical to the rate of diarrhea among Nepali village children, and in fact, children in most developing countries. The study suggests that, despite the efforts to avoid diarrhea that foreigners make, the risk is high over a prolonged period of time.

Traveling in developing countries involves learning to accept things that are beyond your control. As Michael Palin put it, while attempting to travel around the world in 80 days (without flying), "What, in Europe, had been problems to solve, in Egypt became limitations to accept." It is fun to travel, and it is fun to eat, and particularly to discover new foods and tastes, or to share a simple meal with a generous local family. The memories of these adventures, chance meetings, and surprising kindnesses will outlast your memories of being ill. And even your bad memories of illness often become romantically humorous in the retelling (once the episode is far enough behind you).

Do people become immune to traveler`s diarrhea?

There is no question that people produce antibodies against the organisms that cause diarrhea, and eventually become relatively immune. The unanswered questions are how long this process takes, how many exposures to the germ it might take, whether the immunity can be overcome by a high dose, and how long the immunity might last after one leaves the country at risk. Research among expatriates living in Nepal suggests that immunity is acquired slowly: the risk of diarrhea stays the same for 1-2 years, and then slowly decreases over the next 5 years. During that time, expatriates get sick less often—and perhaps more importantly—less severely than when they first arrived.

The fact that immunity can be induced by infections has led to the search for vaccines against diarrheal pathogens. The U.S. Department of Defense has found that diarrheal disease has accounted for the most time lost from functioning compared to any cause in their last few deployments. They are actively pursuing diarrheal vaccines. Several have already been invented and are in the early stages of testing. It would be good to bear in mind that even if these vaccines did not provide 100% protection, they may greatly reduce the severity of the illness, which would allow travelers (and soldiers) to go to new areas with more confidence.

How do you treat traveler`s diarrhea?

As we`ve seen above, traveler`s diarrhea can have several causes. A variety of medications exist to help ease the discomfort and length of traveler`s diarrhea. These are often recommended in a confusing and haphazard way, and people are often told to avoid antibiotics, if possible, and let the infection go away naturally. Some infections may last for a long time without treatment. How can we clarify these issues?

Remember: People with diarrhea don`t want to have diarrhea. This is an important concept when deciding what to recommend to someone who is suffering with diarrhea. The most common causes of diarrhea are the various pathogenic bacteria. These bacteria are all susceptible to antibiotics, but they also are usually self-limiting (that is, they go away by themselves). These two facts lead to a lot of confusion as to how to treat traveler`s diarrhea. If one suspects a bacterial diarrhea, the chances are good that the infection will clear itself in two to seven days. There is just no way to tell whether it will be two or seven (or in a few cases, much longer). In the meantime, you might find yourself pinned to your room and your toilet, unable to finish a meal, and unable to contemplate a bus journey or the start of your trek. Many people might opt for a drug that would end the diarrhea within one day.

Drugs for the treatment of traveler`s diarrhea can be divided into those that provide symptomatic relief, without shortening the infection, and those that are aimed at curing the infection. In the first category are the bowel paralyzers (lomotil, imodium, tincture of opium), and the bulk formers (kaolin and pectate). In the second category are antibiotics. Most bacterial and viral diarrheas are self-limited within a number of days, and symptomatic treatment, or no treatment, may be all that`s necessary, if you are not trying to go anywhere. Protozoal diarrheas tend to be longer lasting, with weeks to months of symptoms without treatment. Symptomatic relief can be obtained, but the infection will go on and on.

It is simplest to think of traveler`s diarrhea as having three treatable syndromes: 1) Bacteria; 2) Giardia; and 3) E histolytica amoeba. In Nepal, from April to October, you can add Cyclospora to this list. The sudden onset of diarrhea that is uncomfortable is likely to be bacterial. The more gradual onset of a prolonged, low-grade diarrhea is likely to be protozoal--either Giardia or E histolytica.

Bacterial diarrhea can be safely cured with an antibiotic. Currently, all the bacteria that can cause traveler`s diarrhea are susceptible to the same antibiotic, so it is not necessary to do cultures to find out what to use. The antibiotics of choice at present are either norfloxacin, or ciprofloxacin, closely related drugs that are known as fluoroquinolones. Some doctors still prescribe sulfamethoxasole-trimethoprim (Bactrim or Septra), but the degree of bacterial resistance to this drug in many countries these days makes it less than an ideal choice. Many studies have shown that the length of illness can usually be reduced to one or two days with treatment. Some bacteria are already starting to become resistant to the fluoroquinolones, particularly Campylobacter in Thailand. When traveling to a destination that has known resistance to ciprofloxacin or norfloxacin, it may be necessary to carry a second antibiotic, or to use an alternative (the current choice is an antibiotic called azithromycin).

Does diet have an effect on traveler`s diarrhea?

The diet most likely to help avoid traveler`s diarrhea would be a diet that excluded human excrement. This diet is fairly standard in developed countries, but is hard to obtain in developing countries. All of the dietary precautions that are listed in many travel books are just details on how to avoid food that might be contaminated with stool. Fruits and vegetables are not inherently contaminated, but the vegetables may have grown in soil that had human feces in it, and the fruit may have been contaminated en route by dirty water or hands. Raw meat is often contaminated, and undercooked meat is dangerous for that reason, and for the possible tapeworm larvae that could be ingested. If you think of all the ways that food could be contaminated by dirty water, dirty hands, and flies, you can begin to think up defensive strategies. Heat can kill bacteria and worm eggs, and if your food is heated sufficiently, and then served before it can become contaminated again, it will b The insides of vegetables and fruits are clean, and that`s why peeling them can make them safe to eat. Lettuce can be soaked in water treated with iodine and rendered safe to eat in that fashion.

Can a change in diet cause diarrhea in travelers? People can have food sensitivities that can lead to diarrhea when they eat specific foods, but this is not very common. It is also likely, in today`s age of ethnic restaurants, that they would have encountered such foods before they traveled. In many cities you can find cuisines ranging from Armenian to Zambian, and most of the time these varied dishes don`t result in diarrhea. Spicy, oily food could lead to a few loose stools, but any seriously uncomfortable or prolonged diarrhea is likely to be due to an infection rather than diet alone. Alcohol in large quantities can sometimes lead to diarrhea, and it can certainly exacerbate any underlying diarrheal illness. You should avoid alcohol if you already have diarrhea. Coffee can also make diarrhea feel worse.

Can a special diet improve diarrhea? Despite generations of folk advice, no one really knows of any diet that can specifically improve diarrhea. Dry toast, white rice, and bananas are often recommended, but there is no science behind this advice. Sometimes people are advised to stop eating altogether. What`s the best thing to do?

People with diarrhea can be divided into two categories: those who feel like eating, and those who don`t. Those who don`t feel like eating should not force themselves, but they must remember to drink fluids. Those who feel like eating should try to do so--why add hunger pangs to your existing level of abdominal discomfort? Try to think of what would sound good to you in your present condition; this will be quite different for different people. Avoid spicy food, alcohol, and coffee. If you eat a certain food, and it makes you feel worse, avoid that food for awhile. Don`t abandon your dietary precautions; you can still get sick with a new bug while suffering from your current bug.

Often, people who are hungry while having diarrhea will experience sudden cramps and an urge to go to the toilet immediately after they start eating. This phenomenon is due to something called the "gastro-colic reflex" and not to the food itself making the diarrhea worse. The gastro-colic reflex is a normal nerve connection between the stomach and the large bowel, which sends a signal for the large bowel to start moving when food enters the stomach. Ordinarily this impulse is controllable. In the presence of diarrhea, however, this signal is exaggerated, and the bowel wants to move uncontrollably. This is a harmless condition, as long as you can find the toilet in the restaurant in time! Once you go to the toilet, your stomach usually settles down, and you can finish eating.

Some people try to eat yoghurt when they have diarrhea. The idea is that yoghurt contains bacteria that can help replenish your gut flora, and help push aside the "bad" bacteria that are causing your illness. There is not much evidence that eating yoghurt makes any real difference in your rate of recovery, but it is an easily digestible food, and probably doesn`t cause harm.

Water purification and personal hygiene.

First time travelers sometimes look upon untreated water as plutonium: even a tiny drop can hurt you. I don`t think this is true. Although all untreated water in developing countries is suspect, not all untreated water is actually contaminated. Some organisms can cause diarrhea even if very few bugs are ingested (such as Shigella, Giardia, and E histolytica). Other bacteria require that a billion to a trillion be ingested at once in order to overcome your stomach acid and cause infection. These bacteria are unlikely to acquired from the random contamination of water.

The simplest thing to do about water when you are traveling is to make up your mind that all water is contaminated, and never drink untreated water. If you never drink untreated water, then water can never be a cause of diarrhea for you. Don`t even brush your teeth with untreated water--this is a kind of Russian roulette. Don`t be unduly concerned about drops of water clinging to freshly washed dishes and glasses, but try to dry them off before using them if you can.

How can you treat potentially contaminated water? There are three main methods of decontaminating water: 1) heat (boiling); 2) chemical disinfection (iodine or chlorine); and 3) filtration. The first two methods are roughly equally effective. Filtration alone almost never renders third world water safe to drink because of the presence of viruses that can`t be filtered. Filtration must be used in conjunction with chemical treatment in this setting. Boiling has the advantage of not altering the flavor of the water, but has the ecological disadvantage of sometimes using firewood in areas where wood is scarce. Chemical decontamination does not require wood or fuel, but can add a slight taste to the water.

There is a lot of confusion about the proper method of boiling water in order to make it safe to drink. Some texts recommend boiling for twenty minutes, others say 10 minutes, of five minutes, and some say it is just necessary to bring it to a boil, even for a few seconds. Some sources warn that you need to lengthen the boiling time as you ascend in altitude. Why is it so confusing?

I think the main source of confusion stems from the fact that there are two different end points in water purification: disinfection (to make it safe to drink), and sterilization (which would make it safe to use in surgery, for example). Since most of us are only worried about quenching our thirst, and not in taking out an appendix, disinfection should be our goal. It turns out that all the organisms that can cause diarrhea begin to be killed at 140 F (65 C). The length of time that water takes to go from 140 F to the boiling point (212 F; 100 C) is sufficient to decontaminate the water for drinking. A few bacteria exist as hardy "spores," which can resist high temperatures for a certain length of time. The boiling time of twenty minutes was suggested in order to sterilize water, and completely eliminate these spores. However, the spores can not cause diarrhea when ingested. Therefore, just bringing water to a boil, at any altitude, renders it safe to drink.

Many brands of filters are marketed to the public to purify drinking water. A filter has to have an absolute filter side of 0.2 microns or less in order to filter out pathogenic bacteria. Giardia and amoebic cysts are easy to filter, as they are 5-8 microns in size. Viruses are more than 8 times smaller than a 0.2 micron filter pore, so they can readily pass through. This is why chemical treatment is necessary in addition to filtration in the third world. However, filtration can have benefit when one is concerned about two particular protozoa, Cryptosporidium and Cyclospora. These two organisms are not killed by iodine, but are large enough to be easily filtered. Cyclospora is a risk in Nepal from mid-April through September, so filtration in addition to chemical treatment might e the best way to go if you are in Nepal during this time.

Chemical treatment with iodine is effective against all other organisms, if you put in the right concentration for the right length of time (follow the directions for whichever system you use). The problem of taste has recently been conquered with the discovery that adding vitamin C (ascorbic acid) to water that has been treated with iodine completely eliminates the taste and the color of the iodine. Make sure that you allow the iodine to complete its job first (for 20 to 30 minutes) before adding the small amount of vitamin C (about 50mg will do the job, but extra is, of course, not harmful).

Is it "bad" to take antibiotics to treat diarrhea?

Fifty years after the discovery of antibiotics, we now have people who are more afraid of the antibiotics than the disease. The ravages of illness in the absence of antibiotics can be seen trekking through any third world village, where one can appreciate children with skin infections oozing pus and blood, adults with constant cough and fever, hands and feet scarred from the ravages of untreated bacterial infections, missing relatives who died from the lack of simple treatments. Why are many Westerners more afraid of the treatment than the disease these days?

I think the answer is that we are so sheltered from seeing the ravages of disease these days, that we no longer fear the illnesses themselves. Instead, we read about the rare ill effects of certain drugs, or dwell upon the fact that these strong "Western" drugs are not "natural." This issue is particularly relevant to traveler`s diarrhea since, for the most part, the disease will go away by itself without treatment. If 85% of traveler`s diarrhea is due to bacterial infection, then most travelers should not have to take antibiotics to treat their diarrhea. The protozoal infections can last much longer, but even some of these can go away by themselves. What we tend to forget, when we talk about "self-limited" illness, is that many other infections can be considered self-limited as well. Many cases of ear infection, sinusitis, bronchitis, and skin infections could all go away if left to themselves in the majority of people. However, people would be sick for weeks to months at a time, develop chronic scarring, and a few people would go on to have life-threatening illnesses in the absence of antibiotic treatment. The point is not entirely that some diseases require antibiotic treatment and others do not, but that antibiotics can relieve suffering.

I have pointed out that most people with diarrhea don`t want to have diarrhea. The question is whether one wishes to endure several days of cramps, frequent explosive stools, loss of appetite and weakness, in order to have a "natural resolution," compared to taking a few antibiotics and being well in one day. In order to make such a decision, one needs to weigh the risks and benefits of antibiotic treatment, versus no treatment at all. This weighing of risks and benefits is how most doctors make decisions in regard to every illness we see, and there is no reason not to apply this reasoning to the problem of traveler`s diarrhea as well.

Inevitably, microorganisms become resistant to the antibiotics that are used to treat them. This battle has been going on since antibiotics were first discovered in the first half of this century. Bacterial resistance is encouraged by the inappropriate use of antibiotics (not enough antibiotics or for too short a time), but resistance will eventually occur even with appropriate use. The highest form of bacterial resistance is found in hospitals, where the same organisms are passed between critically ill patients and treated with the same combinations of antibiotics. The problem of growing antibiotic resistance among microorganisms will not go away.

What is ironic is that many travelers ask their doctors to prescribe an antibiotic to take every day to prevent diarrhea. This use of antibiotics is effective: there is usually a 90% reduction in the incidence of diarrhea on short trips. However, if everyone adopted this approach to traveler`s diarrhea, millions of more doses of antibiotics would be used. The current approach—to treat diarrhea promptly when it occurs, actually decreases the overlal use of antibiotics compared to using antibiotics every day whether you need them or not.

A guide to self-treatment

The definition of adventure travel is to travel to destinations where there is inherent isolation, uncertainty, and risk. Due to the isolation, and the uncertainty of transport and communication, there is a substantial risk that your episode of diarrhea will occur away from medical help. For this reason it is useful to understand how one could diagnose and treat one`s self if medical help is not readily available. From what we have learned above, it is clear that the main decisions to be made is whether the illness is due to food poisoning, bacteria, or protozoa.

Food poisoning can be a violent illness, with the abrupt onset of vomiting, or diarrhea, or--often--both. There can also be fever. But the illness rarely lasts more than 6-12 hours, and by the time you can think about leaving your room to seek help, you generally find that all of the symptoms are disappearing rapidly. No further therapy is required except to rest and re-hydrate yourself as necessary.

Bacterial diarrhea is defined as the sudden onset of relatively uncomfortable diarrhea. Of course there will always be a time when you did not have diarrhea and a time that it began, but bacterial diarrhea can have a more memorable way of starting than a protozoal diarrhea. The onset of uncomfortable cramping and the uncontrollable urge to defecate comes rapidly, and most patients remember the exact time that their illness began. Fever, nausea, and vomiting can also accompany bacterial diarrhea, but they don`t have to be present to make the diagnosis. Occasionally, bacterial diarrhea can be preceded by a day of fever and feeling uncomfortable, with no specific intestinal symptoms. Then the next day the diarrhea begins suddenly.

In contrast to bacterial diarrhea, protozoal diarrhea generally begins slowly, with one or two loose stools, and an absence of fever or vomiting. The affected person wonders whether some infection has been acquired, but the symptoms are tolerable enough that they don`t rush to see a doctor. In our CIWEC Clinic studies we found that the average bacterial diarrhea patient came to see us within 3 days of the onset of their illness, while the average protozoal patient came after two weeks of symptoms. The two main protozoa are Giardia, and Entamoeba histolytica (Amoeba). Giardia is twelve times more common than Entamoeba histolytica amoebas in our practice.

The essence of self-treatment advice is the following:

1. If you have the sudden onset of relatively uncomfortable diarrhea, you probably have bacterial diarrhea and you can treat it with norfloxacin 400mg twice a day for 1-2 days. Ciprofloxacin 500mg twice a day for 1-2 days is equally effective. Bacterial diarrhea and food poisoning can feel the same at first. If you are vomiting, you can`t take an antibiotic in any case. If the vomiting stops and no diarrhea comes, you probably had food poisoning, and no further medication is necessary.


2. If you have the gradual onset of milder diarrhea, you may have a protozoal infection. If your symptoms include a rumbly, gassy feeling, and upper abdominal discomfort, you may have Giardia. The treatment for Giardia differs around the world, depending on availability of certain drugs. Options include metronidazole, tinidazole, albendazole, and quinacrine. Metronidazole is 250mg 3 times per day for 7 days, and tinidazole is 2000mg once a day for 2 days. If your diarrhea alternates every day or so with the absence of diarrhea, or constipation, and you gradually feel more tired and are losing weight, you may have E histolytica. The treatment for E histolytica is with either metronidazole 750mg 3 times per day for 10 days or tinidazole (2000mg per day for 3 days). Both drugs need to be followed by a course of a second drug, either diloxanide furoate (Furamide) 500 mg 3 times a day for 10 days, or paromomycin (Humatin) 500 mg 3 times per day for 10 days.

Diarrhea in Children

Traveling with children is increasingly popular and children can get diarrhea just as easily as their parents can. Infants with diarrhea are more susceptible to dehydration than older children and adults, and one must watch carefully for signs of dehydration and treat with oral rehydration solutions (ORS.) ORS is a mixture of salts, carbohydrates and water that is more readily absorbed from a sick intestine than plain water. Packets of ORS are sold in many camping stores in developed countries and can also be purchased in Nepal. It is important that the ORS powder is mixed with safe water.

Azithromycin is the drug of choice for traveler`s diarrhea in infants and children. It is available in liquid or tablets. We use 10 mg per kilogram, once a day for three days (e.g. a 20-kg child would take 200 mg once a day for three days.) Drugs in the quinolone class (such as norfloxacin or ciprofloxacin) are not recommended for children except in emergencies. [This is because some studies found cartilage damage in young animals who received quinolones; however, quinolones have been used for many years in children with cystic fibrosis without adverse effects on their cartilage.] Nalidixic acid has also been used safely in children. An effective dose is 50 mg per kilogram per day in three divided doses for two days. Thus, the dose for a 12-kg child would be calculated as follows: 50 X 12 = 600 mg per day, divided into three doses, which results in 200mg three times a day for two days. Children with a history of seizures should not take nalidixic acid.

Rifaximin is a non-absorbable antibiotic that is approved for the treatment of non-invasive traveler`s diarrhea in children over 12 years. However, it is not effective against invasive organisms such as Campylobacter, a relatively common cause of diarrhea among travelers to Nepal. Therefore, the role of rifaximin in the treatment of diarrhea in children traveling to Nepal is limited.

Children with Giardia or E histolytica can safely take metronidazole benzoate, which is available as a liquid. The dose is 15 mg per kilogram per day, in three doses. We treat Giardia for five days and E histolytica for 7 days. Nursing infants should continue to nurse while they have diarrhea.

Traveler`s Diarrhea while Pregnant or Nursing

Traveling in a developing country while pregnant is a calculated risk. The decision to travel to a high-risk destination while pregnant should not be taken lightly. If you choose to do so, make sure you have a discussion with a reliable health professional before you go.

Pregnant women may be more susceptible to traveler`s diarrhea or its complications for a variety of reasons. For example, the lower acidity of the stomach during pregnancy may make it easier for bacteria to survive in the stomach. In addition, it is common for pregnant women to experience nausea and this may limit fluid intake and increase the risk of dehydration. Severe dehydration in the pregnant woman can diminish blood flow through the placenta.

Despite the fact that pregnant women may be at higher risk of traveler`s diarrhea, treatment options are more limited. All pregnant women with diarrhea should carefully watch for dehydration and drink ORS (described in the section on Diarrhea in Children.) The antibiotic azithromycin is safe in pregnancy and is often used to treat pregnant women with genital infections. It is therefore the best available antibiotic for pregnant women with bacterial diarrhea. Ciprofloxacin, norfloxacin and other drugs in the quinolone class cannot be taken while pregnant. Although rifaximin is not absorbed, it is not approved for use during pregnancy. Metronidazole should be avoided during the first trimester but may be used in the second or third trimester if necessary. Paromomycin is safe in pregnancy and can sometimes cure a Giardia or E histolytica infection although it is not always successful.

A woman who is nursing a child can generally take antibiotics without risk to the child. The child may get a tiny exposure but not enough to do any harm. Do not take medications lightly while pregnant or nursing and always consult a reliable authority first.

Food and water precautions are very important for the pregnant woman. Even if being careful about what you eat or drink doesn`t guarantee you won`t get diarrhea, it might help prevent other food or water borne infections such as hepatitis E or Listeria, both of which can be particularly dangerous during pregnancy.

Other causes of traveler`s diarrhea

We have so far discussed the most common causes of diarrhea in travelers. A few other causes exist, however. Cryptosporidium is a protozoa that can cause a diarrheal illness somewhat similar to Giardia that can last for several weeks. There is no effective treatment at present, but the illness does go away by itself. Cryptosporidium is not a common cause of diarrhea in travelers.

Dientamoeba fragilis is a protozoa that can cause a mild but persistent diarrhea that can last for one or two months. It is difficult to identify this organism with certainty, but it does respond to treatment with tetracycline, 250 mg four times per day for 10 days.

Cyclospora is a recently discovered cause of diarrhea that is a significant cause of diarrhea in the late spring and early summer in Nepal, Haiti, and Peru. It can cause a prolonged illness (average 6 weeks) that is associated with profound fatigue and loss of appetite, and intermittent diarrhea. It can be treated with trimethoprim-sulfamethoxazole (also known as Bactrim or Septra) in a twice daily dose for seven days.

Intestinal worms almost never cause diarrhea, and worm eggs are only seen in about 5% of stool samples at the CIWEC Clinic.

One final organism, called , is worth mentioning. Some doctors feel that B hominis can cause intestinal symptoms and is worth treating. We have been studying B hominis since 1985, and have found no connection between the presence of this organism in the stool and any particular clinical symptoms. We find it equally often in the stools of patients who are perfectly well. We find it in about one-third of all stool samples, and we ignore it. If you return home with intestinal symptoms and B hominis is found on a stool sample, you will be better served by trying to find another cause for your symptoms. There is no sure treatment for B hominis, although metronidazole is used most often.

Tropical sprue

Tropical sprue is a poorly understood illness that is thought to be an infection with an organism that has not yet been identified. The illness is associated with chronic diarrhea and weight loss, and is suspected when treatment for other causes of diarrhea have not been successful. The illness causes malabsorption of food from the small intestine, and there is a simple test, the d-xylose absorption test, that can determine if there is malabsorption in the small bowel. If the d-xylose test shows a problem with the absorption of xylose, it is likely that the patient has tropical sprue. This condition can be treated with a combination of tetracycline and a vitamin called folic acid.

Returning home with diarrhea

Sometimes your trip will end before your diarrhea does. At that point you may find yourself in your home country facing doctors who don`t have a sound approach to the traveler with diarrhea. Following the approach that has been outlined in this article is a good way to start. If the symptoms persist even after treating for the most likely cause, you may need a more extensive evaluation.

However, most of the time this further evaluation sheds no further light on the problem. It can also be very expensive. It is true that some travelers have a persistent change in their bowel habits after a trip to a developing country. They may have loose stools, or urgent stools, or more frequent stools. They may be sensitive to certain foods, getting gas or diarrhea after eating them. This condition appears similar to other forms of unexplained diarrhea and abdominal discomfort that have been labeled "irritable bowel syndrome." After all infectious causes of diarrhea have been eliminated due to appropriate investigation or treatment, the problem becomes one of controlling and learning to live with the symptoms. Most of these unfortunate travelers get better within a year, but a very few have ongoing symptoms.

Research into traveler`s diarrhea: the future

Prevention and treatment of traveler`s diarrhea is firmly based on figuring out the causes. As we noted above, a specific cause for diarrhea in a traveler is found in only 60-80% of cases, depending on the region of travel, and the amount of effort spent isolating organisms. The remaining 20-40% of people clearly have an infection; we just can`t find the exact organism yet. The discovery of Cyclospora at the CIWEC Clinic was a small step toward filling in this uncharted territory.

Finding the exact causes of traveler`s diarrhea is important because of an exciting new prospect for preventing diarrhea: by taking an oral vaccine. Oral vaccines, either as a pill or a liquid, already exist for cholera and Enterotoxigenic E coli (ETEC). Oral vaccines for Shigella and Campylobacter are being developed. This type of approach could have a huge economic effect on developing countries, especially countries like Nepal that are highly dependent on tourism. With less fear of illness, travelers would have a lower threshold for planning a trip to these otherwise thrilling destinations, and the flow of money would replace the flow of diarrhea.

Research into prevention of diarrhea by other means has proven remarkably difficult to carry out. With tourists eating three meals a day in various restaurants, and the incubation periods of pathogenic organisms ranging from days to weeks, it remains difficult to determine where people get sick. However, in the developed world there are strict rules for restaurant management and hygiene that are aimed at interrupting the flow of microorganisms from the food chain to the intestines of customers. The principles that have been developed, such as not storing food at room temperature, frequent cleaning of counters and machinery, separate "clean" and "dirty" preparation areas, etc., work very well. Unfortunately, they are not applied in developing countries, where they are needed the most. I believe that research into how to develop appropriate third world restaurant training and hygiene would be the most effective means of cutting down on diarrhea in travelers.

If you have any questions you can contact one of the CIWEC physicians by e-mailing us at ciwecclinic@mail.com.np