Water hazards

Steve Garro is glad he drank as much beer as he did during his nine weeks in South America. Traveling by bicycle through Bolivia, Chile, and Peru with three others, the Flagstaff, AZ, resident is a good example of why not to drink the water. “I didn’t drink anything but Fanta or beer, especially after seeing the Rio Chuquia in La Paz turn a foamy blue and orange. The locals wash their fruits and vegetables in that river,” Garro says. His buddies were a bit more lax, occasionally trying street vendor food and salads. The end result: Only Steve avoided being laid up for days with what was apparently traveler’s diarrhea (TD).

At least 3 out of 10 people who travel to the tropics get TD. The loose stools, often 4–5 a day, usually strike during the first week of travel. TD typically lasts three or four days, with 90% of cases resolving within a week. It strikes most often in the developing countries of Latin America, Africa, the Middle East, and Asia.

“Almost all traveler’s diarrhea is transmitted by a person ingesting small amounts of feces—it may only be a gram, but the water is contaminated with fecal organisms,” says Caryn Bern, medical epidemiologist at the Centers for Disease Control and Prevention’s (CDC’s) National Center for Infectious Diseases in Atlanta. More than a dozen common organisms cause TD, says Bern. So, although research shows that expatriates in a developing country develop immunity to many organisms, it may be impossible for the frequent traveler to build immunity to all the common organisms.

According to the CDC, bacterial pathogens cause approximately 80% of the cases, with parasites and viruses rounding out the rest. “If you go to a developing country such as India, Peru, or Kenya and look at children who are not growing up in a rich family, by the time they’re 5, most have had between 15 and 20 episodes of diarrhea from a whole assortment of organisms,” says Bern. In comparison, “A person who grows up in a clean environment without pathogens has had maybe 3–5 episodes of diarrhea, mostly viral.”

The presence of blood or pus in the stool or high fever can suggest an invasive pathogen such as Salmonella, Shigella, or E. coli, in which case an antibiotic such as trimethoprim (Bactrim/Septra) or ciprofloxacin (Cipro) may be indicated. Unless there is severe diarrhea, most people should go easy on the loperamide (Imodium) or Lomotil because its slowing of the transit time may prolong the illness. If the diarrhea occurs 5 or more times a day, the need for oral rehydration may prompt medical attention.

Typhoid fever, also called enteric fever, requires medical attention. Although it strikes less than 1 in 5000 travelers in the highest-risk areas, it is a severe and prolonged illness known for fevers that can exceed 104 °F. In typhoid fever, Salmonella typhi bacteria incubate for 1–2 weeks as they spread through the lymphatic system. The body’s defense system, the reticuloendothelial cells, clear out the early phase of the bacteria, but the hardy S. typhi continue to multiply, reinfecting the bloodstream and intestinal tract. Complications include bleeding and perforation of the intestines. But bacterial organisms are not the only water contamination concerns; other potential pathogens include amoebas, flukes, and viruses.

Patricia McCreary wishes she hadn’t taken that drink of river water on a whitewater rafting trip in Peru. The water that looked so crystal clear and benign contained giardia cysts, 10- to 20-µm-sized amoebas—a size that Bern calls large in the world of pathogens.

Cysts are the infective form of protozoa, and they can survive for weeks to months in moist surroundings, resisting gastric acid and typical chlorine levels. In the small intestine, the cysts transform into larger, more unstable trophozoites, which have a prominent “sucking disk” on their surface that helps them adhere to the intestine. Seven to 21 days after onset, explosive diarrhea hits as the giardia damage the intestinal lining enough to prevent normal food absorption.

McCreary’s symptoms included loose, foul-smelling stools with distention, flatulence, and cramps. Giardiasis’sincidence in developing countries is 7–10%, and it is often asymptomatic in children. Giardia are also prevalent in many American waterways, where mammalian fecal matter is believed to be the source.

Most parasitic amoebas are cosmopolitan, flourishing in rural and urban environments. Another common amoebic disorder is amebiasis (an infection caused by Entamoeba histolytica), which is prevalent in Africa and remote Asia. The drug of choice for giardiasis and amebiasis is metronidazole (Flagyl) in high doses, which leaves most people nauseated during the 5–7 day regimen. Indeed, many patients complain that the Flagyl dose creates as much discomfort as the giardiasis.

Figure 1. Schistosome life cycle. Borne in waters carrying fecal waste, the schistosome parasite goes through several stages during its life cycle, passing from human hosts to snails and back again.

Flukes or trematodes are long-lived parasites, which in the most common blood fluke disease, schistosomiasis, penetrate wet human skin during contact with freshwater inhabited by infected snails (Figure 1). Once the trematodes enter the skin, they migrate through the body and incubate for 4–6 weeks; eggs are then deposited by the female worms in the intestine or bladder and passed outside to spread further.Light infections may be asymptomatic, and the worms can persist in the host for decades. But long-term problems are a concern because eggs can lodge in various organs, such as the intestinal wall or spinal cord, and cause fibrosis, the growth of connective tissue.

Schistosomiasis affects approximately 200 million people worldwide and causes many deaths in rural areas. The good news is that schistosomiasis is particular to certain locations, and people are aware of it. For example, S. japonicum is endemic in parts of the Philippines and China, while pockets of S. haematobium are found in the Middle East and Africa.

Fortunately, the drug praziquantel (Biltricide) is effective against all forms of schistosomiasis. Prevention is best accomplished by avoiding water contact in areas infested by schistosomiasis. According to The Travel & Tropical Medicine Manual, rapid toweling to dry the skin may keep parasites from penetrating if accidental immersion occurs.

According to the CDC, travelers commonly acquire viruses but often do not feel symptoms. The various forms of viral hepatitis create further concern. Of these, hepatitis A is the most common waterborne hepatitis virus in tropical countries. Rapid onset of fatigue and gastrointestinal symptoms often strikes adults 3–4 weeks after contamination, whereas children may show no symptoms. Jaundice is also common. Fran Hunkins, a former Peace Corps volunteer in central Brazil, wasn’t feeling peppy but didn’t realize she had it. “We knew lots of kids in our village were running around with it. The local pediatrician stopped me, looked at my yellow eyes and said, ‘You’ve got hepatitis,’” she says.

Although it went away in time, Hunkins learned why alcohol consumption is discouraged for a year. A fruity alcoholic drinkin Brazil after she recovered and another mixed drink in the United States six months later caused a full-blown return of her hepatitis. “I relapsed the day after both drinks. I would have gotten over it much faster if I hadn’t drunk that alcohol.” Statistics show that in 90% of cases, liver function tests return to normal within 12 weeks, which is fortunate because a specific treatment is lacking. Luckily, the advance of hepatitis A to often-fatal fulminant hepatitis is infrequent.

David Mozer, a Seattle resident and former Peace Corps volunteer, has returned to Africa more than 40 times to lead bicycle tours as director of Bicycle Africa. Mozer got diarrhea half a dozen times during his two-year Peace Corps stint in Liberia. When he returns for the tours, he knows his water sources. “I don’t drink surface water, but if it’s groundwater 100 m down, I drink it. If it’s a borehole well put in by development agencies, that’s deep enough,” he says. “I’m actually more concerned about restaurants and the water in cities than in the villages.” Mozer encourages his groups to be especially careful during the first several days, when the body is tired and adjusting. It apparently works. “We have a remarkably low incidence of traveler’s diarrhea,” he says.

“Boil it, cook it, peel it, or forget it” is one popular saying for remembering preventive measures. Drink boiled water (boiled vigorously for 1 min), bottled water, or canned drinks. Iodine-treated water is an alternative but may not kill the potential TD bacteria, cryptosporidia, unless the water sits for 15 h before consumption. Other CDC recommendations: Wash hands frequently; eat only thoroughly cooked food, fruit, and vegetables you have peeled yourself; and avoid ice, street vendor food, and dairy products unless pasteurized. Also, do not swim in freshwater. Travelers should check the CDC Web site for vaccinations or precautions to take for their particular travel destination.

Garro and his foursome all had 0.1-µm or smaller portable filters that remove bacteria and protozoa but not viruses. “I filtered stuff that was really foul,” said Garro, who obviously felt proud that he came home without stories of diarrhea or nausea.

• Guerrant, R.; Walker, D.; Weller, P. Essentials of Tropical Infectious Disease; Churchill Living-stone: Kent, U.K., 2001.
• Jong, E.; McMullen, R. The Travel & Tropical Medicine Manual; W. B. Saunders: St. Louis, MO, 1995.
• Visit the CDC’s National Center for Infectious Diseases at www.cdc.gov/travel and www.cdc.gov/travel/foodwater.htm.