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Wilderness diarrhea (WD), also called wilderness-acquired diarrhea (WAD) or backcountry diarrhea, is a variety of traveler’s diarrhea (TD) in which backpackers, hikers, campers and other outdoor recreationalists are infected during temporary visits to relatively remote natural areas. Risk factors include drinking untreated surface water and failure by the individual and his or her companions to maintain personal hygiene practices and clean cookware. Most cases are self-limited and the cause is most often never known. Some medical and public health researchers believe that the risks of WD have been over-stated and are poorly understood by the public.
Names and definitions
As a variety of travelers' diarrhea, "wilderness diarrhea" is a form of infectious diarrhea, itself classified as a type of secretory diarrhea. These are all considered forms of gastroenteritis. The term may be applied in various remote areas of non-tropical developed countries (U.S., Canada, western Europe, etc.), but is less applicable in developing countries, and in the tropics, because of very different pathogens likely to be encountered there.
The term "backpacker’s diarrhea" might be an appropriate synonym for "Wilderness Diarrhea," but medical literature has traditionally reserved that term, with fair consistency, for giardiasis — a specific cause of "wilderness diarrhea."
Causes
There are three vectors for human infection by pathogens that cause WD: fecal-oral transmission, water, and contaminated food. The major factor governing the amount of pathogen pollution in surface water is human and animal activity in the watershed. The most common pathogens that cause WD are Giardia and Cryptosporidium. Other infectious agents may play a larger role than generally believed and include Campylobacter, hepatitis A virus, hepatitis E virus, enterotoxogenic E. coli, e. coli 0157:H7, Shigella, and various viruses. More rarely, Yersinia enterocolitica, Aeromonas hydrophila, and Cyanobacterium may also cause disease.
Giardia lamblia, a common cause of WD, does not tolerate freezing and can remain viable for nearly three months in river water when the temperature is 10°C and about one month at 15–20°C in lake water. Cryptosporidium, another WD pathogen, has been shown to survive in cold waters (4°C) for up to 18 months, and can even withstand freezing, although its viability is thereby greatly reduced.
Many other varieties of diarrhea-causing organisms, including Shigella and Salmonella typhi, and hepatitis A virus, can survive freezing for weeks to months. Virologists believe all surface water in the United States and Canada has the potential to contain human viruses, which cause a wide range of illnesses including diarrhea, polio and meningitis.
It may be difficult to causally associate a particular case of diarrhea with a recent wilderness trip lasting only a few days because the incubation time may take longer than the length of time of the trip. Studies of long trips into the wilderness, where the trip time is much longer than the mean incubation time of the disease, are less susceptible to these types of errors since the diarrhea is more likely to occur while the person is still in the wilderness.
Giardia is ubiquitous outside of wilderness settings, and may affect 7.5 million Americans at any one time. According to a different estimate, about 7% of Americans are infected with giardia from all sources, wilderness and otherwise, although as few as 5% of an infected population may develop symptoms. It is mainly spread by fecal-oral or food-borne transmission. More than 34,000 cases were reported to state health departments in 1991, of which 19 outbreaks were waterborne, and two affected backpackers or campers.
A meta-analysis was performed, with an initial screening of 104 articles, in which nine met inclusion criteria for epidemiological analysis. Of the nine articles that were analyzed, neither of two case reports (report of the diagnosis, treatment, and follow-up of an individual patient) met the criteria of the Centers for Disease Control for waterborne disease outbreak. Two "prospective" studies (data on subjects who were followed forward in time) showed no significant association of backcountry water with infection. Of four studies that included control groups, none showed a significant relationship between backcountry water and infection. The conclusion was that North American wilderness waters are not a source of giardiasis.
Degree of risk
The risk of acquiring diarrhea in the wilderness arises from inadvertent ingestion of pathogens. Studies have been done to estimate diarrhea rates of wilderness travelers but for the most part they have either focused on only one pathogen, giardia lamblia, or provided scant data. A notable exception is a study of Appalachian Trail hikers.
Appalachian Trail Study
An epidemiological study of 280 long-distance hikers who each logged an average 139 days on the Appalachian Trail found that diarrhea was experienced by 56% of the cohort. The occurrence of diarrhea was positively associated with the duration of exposure in the wilderness. The diarrhea rate was reduced among those who either consistently treated their drinking water or had good personal hygiene.
Those who consistently treated their water had a diarrhea rate of 45% compared to 69% for those who did so inconsistently. The worst diarrhea rate of 86% was among those who drank untreated surface water (streams or ponds) more than several times a week.
Those who washed their hands with soap and water routinely after defecation had a 36% diarrhea rate compared to 59% for those who didn't.
Other Studies
Studies of shorter duration hikes resulted in a lower rate of infection or illness, which is expected because of less exposure. In one study, an illness rate of 3-5% was found.. Another study of backpackers in California found a Giardia infection rate of 5.7% but no symptomatic giardiasis. An additional 16.7% of subjects in the California study developed mild gastrointestinal illness, but no Giardia infection.
In a separate project at Grand Teton National Park, visitors suffering from active gastrointestinal complaints were invited to a free clinic. Of 178 cases tested, Campylobacter was the most common agent isolated at 28%, followed by Giardia at 8%. Salmonella and Shigella were not isolated and 69% of subjects had no identifiable pathogen.
In a 1991 giardiasis survey of 48 state health departments in the United States, 34,348 cases were reported. Of these, 19 were attributed to contaminated drinking water and 2 were reported among campers and backpackers.
Ingesting 10 – 25 Giardia cysts results in a 33% risk of detectable cysts in stools, and a significantly smaller risk of symptomatic giardiasis. Between 0.108 and 0.003 Giardia cysts per liter of water were measured in a 1984 survey of 18 backcountry sites in California's Sierra Nevada. The same survey detected no Giardia at 66 additional sites. Another survey completed in 1990 of three Sierra Nevada sites on 10 different dates, found concentrations between 0.0 and 0.62 cysts per liter. An additional survey by Backpacker Magazine of several backcountry sites was completed in 2003. The highest concentration that survey found was 1.5 Giardia cysts per liter. Drinking seven liters of such water may result in a minimum infective dose.
Symptoms
The incubation period for giardiasis averages about 14 days and that of cryptosporidiosis about seven days. Certain other bacterial and viral agents have shorter incubation periods, although hepatitis may take weeks to manifest itself. The onset usually occurs within the first week of return from the field, but may also occur at any time while hiking.
Most cases begin abruptly and usually result in increased frequency, volume, and weight of stool. Typically, a hiker experiences at least four to five loose or watery bowel movements each day. Other commonly associated symptoms are nausea, vomiting, abdominal cramping, bloating, low fever, urgency, and malaise, and usually the appetite is affected. The condition is much more serious if there is blood or mucus in stools, abdominal pain, or high fever. Dehydration is a possibility. Life-threatening illness coming from WD is extremely rare.
Treatment
WD is typically self-limited, generally resolving without specific treatment. Oral rehydration therapy with rehydration salts is often beneficial to replace lost fluids and electrolytes. Clear, disinfected water or other liquids are routinely recommended.
Hikers who develop three or more loose stools in a 24-hour period — especially if associated with nausea, vomiting, abdominal cramps, fever, or blood in stools — should be treated by a doctor and may benefit from antibiotics, usually given for 3–5 days. Alternately, a single dose azithromycin or levofloxacin may be prescribed. If diarrhea persists despite therapy, travelers should be evaluated and treated for possible parasitic infection.
There is no effective antibiotic against Cryptosporidium, which can be quite dangerous to patients with compromised immune systems.
Prevention
Since WD can be caused by fecal-oral transmission, contaminated water, and contaminated food, prevention methods should address these causes. Also it was found that on very long trips, taking multivitamins was associated with a reduction of WD.
The risk of fecal-oral transmission of pathogens can be reduced by good hygiene. This includes: washing hands after urination and defecation; and washing eating utensils with warm soapy water. Additionally a three-bowl system can be used for washing eating utensils.
Authoritative guidelines caution that safety judgments cannot reliably be made based on the mere appearances of a water source. One key to prevention is therefore various filters and chemical treatments. (see Portable water purification). The choice depends upon the number of people involved, space and weight considerations, the quality of available water, personal taste and preferences, and fuel availability. If Giardia lamblia is an uncommon isolate and WAD (wilderness-acquired diarrhea) is infrequent, then it may not be cost effective to recommend filtering for recreationalists involved in short-duration trips. Careful attention to personal hygiene can help prevent the spread of infection.
In a study of long-distance backpacking, it was found that water filters were used more consistently than chemical disinfectants. Inconsistent use of iodine or chlorine may be due to disagreeable taste, extended treatment time or treatment complexity due to water temperature and turbidity.
Because methods based on halogens, such as iodine and chlorine, do not kill Cryptosporidium, and because filtration misses some viruses, the best protection may require a two-step process of either filtration or coagulation-flocculation, followed by halogenation. Boiling is effective in all situations, but won't improve the water's taste.
Iodine resins, if combined with microfiltration to remove resistant cysts, are also a viable single-step process, but may not be effective under all conditions. New one-step techniques using chlorine dioxide, ozone, and UV radiation may prove effective, but still require validation.
Ultraviolet (UV) light for water disinfection is well established and widely used for large applications, like municipal water systems. A small portable UV device, called a Steri-pen, is now available for hikers. According to the manufacturer, it meets standards set forth in the U.S. EPA Guide Standard and Protocol for Testing Microbiological Water Purifiers.
In summary, both careful attention to personal hygiene and water treatment have been shown to be important for preventing wilderness diarrhea.
Water disinfection
Two standard textbooks on backcountry medical issues promote water disinfection as a key means of preventing infection. Various commercial water treatment devices are described in detail, and most infectious diarrhea acquired in the U.S. wilderness is considered to be from water-borne pathogens, and effective prevention is therefore thought to require treatment of drinking water as well as proper sanitiation.
Drinking untreated water is something like Russian roulette. Giardia in wilderness water sources may probably not be as prevalent as once believed but it's still present. If a wilderness visitor is confident of untainted alpine water, it's probably safe to drink it untreated, but in areas with significant human or animal activity, treatment is critical in prevention.
Contamination of U.S. backcountry water sources is widespread and disinfection is necessary but exaggerated concern has been raised about the issue. An example is an alleged case where Government agencies have filtered hundreds of gallons of water from wilderness streams, found one or two organisms (far less than enough to be infective), and erected garish signs proclaiming the water hazardous.
See also
References
- Backer, Howard D. (2007). "Chapter 61: Field Water Disinfection". In Auerbach, Paul S. ed. (ed.). Wilderness Medicine (5th edition ed.). Philadelphia, PA: Mosby Elsevier. pp. 1368–1417.
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Footnotes
- ^ Zell SC (1992). "Epidemiology of Wilderness-acquired Diarrhea: Implications for Prevention and Treatment" (PDF). J Wilderness Med. 3 (3): 241–9.
- ^ Hargreaves JS (2006). "Laboratory evaluation of the 3-bowl system used for washing-up eating utensils in the field". Wilderness Environ Med. 17 (2): 94–102. PMID 16805145.
Diarrhea is a common illness of wilderness travelers, occurring in about one third of expedition participants and participants on wilderness recreation courses. The incidence of diarrhea may be as high as 74% on adventure trips. …Wilderness diarrhea is not caused solely by waterborne pathogens, … poor hygiene, with fecal-oral transmission, is also a contributing factor
- (Backer 2007, p. 1374)
- (Backer 2007, p. 1369)
- Prepared by Federal-Provincial-Territorial Committee on Drinking Water of the Federal-Provincial-Territorial Committee on Health and the Environment (2004) (2004), "Protozoa: Giardia and Cryptosporidium" (PDF), Guidelines for Canadian Drinking Water Quality: Supporting Documentation, Health Canada, retrieved 2008-08-07
{{citation}}: Cite has empty unknown parameters:|coeditors=and|coauthors=(help)CS1 maint: numeric names: authors list (link) - Dickens DL, DuPont HL, Johnson PC (1985). "Survival of bacterial enteropathogens in the ice of popular drinks". JAMA. 253 (21): 3141–3. PMID 3889393.
{{cite journal}}: Unknown parameter|month=ignored (help)CS1 maint: multiple names: authors list (link) - Backer H (2000). "In search of the perfect water treatment method". Wilderness Environ Med. 11 (1): 1–4. PMID 10731899.
- Gerba C, Rose J (1990). "Viruses in Source and Drinking Water". In McFeters, Gordon A. ed. (ed.). Drinking water microbiology: progress and recent developments. Berlin: Springer-Verlag. pp. pp 380-399. ISBN 0-387-97162-9.
{{cite book}}:|editor=has generic name (help);|pages=has extra text (help) - White, George W. (1992). The handbook of chlorination and alternative disinfectants (3rd edition ed.). New York: Van Nostrand Reinhold. ISBN 0-442-00693-4.
{{cite book}}:|edition=has extra text (help) - ^ Boulware DR, Forgey WW, Martin WJ 2nd (2003). "Medical Risks of Wilderness Hiking". Am J Med. 114 (4): 288–93. PMID 12681456.
{{cite journal}}: CS1 maint: multiple names: authors list (link) CS1 maint: numeric names: authors list (link) - ^ Boulware DR (2004). "Influence of Hygiene on Gastrointestinal Illness Among Wilderness Backpackers". J Travel Med. 11 (1): 27–33. PMID 14769284.
- Brody, Jane E. (1989). "HEALTH: Diagnostics; Test Unmasks a Parasitic Disease". NY Times. Retrieved 2008-08-07.
{{cite news}}: Cite has empty unknown parameter:|coauthors=(help) - ^ Rockwell, Robert L. (2003). "Giardia Lamblia and Giardiasis With Particular Attention to the Sierra Nevada". Peak Climbing Section, Loma Prieta Chapter, Sierra Club. Retrieved 2008-08-07.
- ^ Welch TR, Welch TP (1995). "Giardiasis as a threat to backpackers in the United States: a survey of state health departments". Wilderness Environ Med. 6 (2): 162–6. PMID 11995903.
{{cite journal}}: Unknown parameter|month=ignored (help) - Welch TP (2000). "Risk of giardiasis from consumption of wilderness water in North America: a systematic review of epidemiologic data". Int. J. Infect. Dis. 4 (2): 100–3. PMID 10737847.
- ^ Welch TR (2004). "Evidence-based medicine in the wilderness: the safety of backcountry water" (PDF). Wilderness Environ Med. 15 (4): 235–7. PMID 15636372.
- Zell, S. C. (1993). "Cyst acquisition rate for Giardia lamblia in backcountry travelers to Desolation Wilderness, Lake Tahoe". Journal of Wilderness Medicine. 4 (2): 147–54.
{{cite journal}}: Unknown parameter|coauthors=ignored (|author=suggested) (help) - Sanders JW, Frenck RW, Putnam SD; et al. (2007). "Azithromycin and loperamide are comparable to levofloxacin and loperamide for the treatment of traveler's diarrhea in United States military personnel in Turkey". Clin. Infect. Dis. 45 (3): 294–301. PMID 18688944.
{{cite journal}}: Explicit use of et al. in:|author=(help); Unknown parameter|month=ignored (help)CS1 maint: multiple names: authors list (link) - ^ Adachi, Javier A. (2007). "Infectious Diarrhea from Wilderness and Foreign Travel". In Paul S. Auerbach (ed.). Wilderness Medicine. p. 1418.
{{cite encyclopedia}}: Unknown parameter|coauthors=ignored (|author=suggested) (help) Cite error: The named reference "Adachi2007" was defined multiple times with different content (see the help page). - Backer H (2002). "Water disinfection for international and wilderness travelers". Clin. Infect. Dis. 34 (3): 355–64. PMID 11774083.
{{cite journal}}: Unknown parameter|month=ignored (help) - (Backer 2007, p. 1411)
- Wood, T. D. (2008). "Water: What Are the Risks?". REI.com. Retrieved 2008-08-07.
- Seattle, Washington: The Mountaineers Books, 5th edition, 2001