Wilderness and diarrhea

Diarrhea acquired in the wilderness, sometimes calledWilderness diarrhea (WD), wilderness-acquired diarrhea (WAD) or backcountry diarrhea, and is a much-discussed hazard among backpackers, hikers, campers and other outdoor recreationalists who visit wilderness areas in temperate climates of the developed world.cite journal |author=Zell SC |title=Epidemiology of Wilderness-acquired Diarrhea: Implications for Prevention and Treatment |journal=J Wilderness Med |volume=3 |issue=3 |pages=241–9 |year=1992 |url=http://www.wemjournal.org/pdfserv/i0953-9859-003-03-0241.pdf|doi= ] Fact|date=July 2008 | Is this the correct definition for "wilderness diarrhea"? Other ref does not discuss "wilderness diarrhea", only discusses "wilderness-acquired diarrhea". See Discussion. 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.cite journal |author=Hargreaves JS |title=Laboratory evaluation of the 3-bowl system used for washing-up eating utensils in the field |journal=Wilderness Environ Med |volume=17 |issue=2 |pages=94–102 |year=2006 |pmid=16805145 |doi= |url=http://www.wemjournal.org/wmsonline/?request=get-document&issn=1080-6032&volume=017&issue=02&page=0094 |quotation=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] 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. [cite web |url=http://www.yosemite.org/naturenotes/Giardia.htm |title=Yosemite Association - Nature Notes: Giardia |format= |work= |accessdate=]

Names and definitions

Diarrhea acquired in the wilderness is typcally 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.

Causes

Infectious diarrhea acquired in the wilderness is caused by various bacteria, viruses and parasites, the most common of which are thought to be "Giardia" and "Cryptosporidium".Fact|date=October 2008 Other infectious agents may play a larger role than generally believed [cite journal |author=Zell SC |title=Epidemiology of wilderness-acquired diarrhea: implications for prevention and treatment |journal=Journal of Wilderness Medicine |volume=3 |issue=3 |pages=241–9 |year=1992 |url=http://www.wemjournal.org/pdfserv/i0953-9859-003-03-0241.pdf] 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. [harvard citation|Backer|2007|Ref=none|p=1369] Vectors for all of these causes are limited to fecal-oral transmission, and contaminated water and food. The major factor governing pathogen content of surface water is human and animal activity in the watershed. [harvard citation|Backer|2007|Ref=none|p=1374] .

ymptoms

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.

Diagnosis

It may be difficult to associate a particular case of diarrhea with a recent wilderness trip of a few days because incubation of the disease may outlast the trip. Studies of trips that are much longer than the average incubation period are less susceptible to these errors since there is enough time for the diarrhea to occur during the trip. To cause giardiasis, Giardia requires an incubation period of one to two weeks (average seven days), [http://www.cdc.gov/ncidod/dpd/parasites/giardiasis/factsht_giardia.htm#symptoms_begin] while Criptosporidium requires an average of seven days to cause cryptosporidiosis. [http://www.cdc.gov/crypto/disease.html] Other bacterial and viral agents have shorter incubations, although hepatitis may require weeks.

A suspected case of wilderness diarrhea may be assessed within the general context of intestinal complaints. During any given four-week period, as many as 7.2% of Americans may experience some form of infectious or non-infectious diarrhea [http://www.cdc.gov/enterics/publications/240-scallan_2004.pdf] . There are an estimated 99 million annual cases of intestinal infectious disease in the United States [cite journal |author=Garthright WE, Archer DL, Kvenberg JE |title=Estimates of incidence and costs of intestinal infectious diseases in the United States |journal=Public Health Rep |volume=103 |issue=2 |pages=107–15 |year=1988 |pmid=3128825 |pmc=1477958 |doi= |url=] , most commonly from viruses, followed by bacteria and parasites, including Giardia and Cryptosporidium. Giardia alone may infect up to 10% of Americans at any one time. However, because most carriers are asymptomatic, [http://query.nytimes.com/gst/fullpage.html?res=950DE7DC1F3AF935A15753C1A96F948260&scp=5&sq=giardia&st=cse] , there are only an estimated 2 million U.S. cases of symptomatic giardiasis annually [http://www.cdc.gov/mmwr/preview/mmwrhtml/ss5401a2.htm] , spread mostly by fecal-oral or food-borne transmission. cite web |url=http://lomaprieta.sierraclub.org/pcs/articles/giardia.asp |title=Giardia Lamblia and Giardiasis With Particular Attention to the Sierra Nevada |accessdate=2008-08-07 |last=Rockwell |first=Robert L. |date=2003 |work=Peak Climbing Section, Loma Prieta Chapter, Sierra Club ]

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.cite journal |author=Sanders JW, Frenck RW, Putnam SD, "et al" |title=Azithromycin and loperamide are comparable to levofloxacin and loperamide for the treatment of traveler's diarrhea in United States military personnel in Turkey |journal=Clin. Infect. Dis. |volume=45 |issue=3 |pages=294–301 |year=2007 |month=August |pmid=18688944 |doi= |url=] 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 wilderness-acquired diarrhea can be caused by fecal-oral transmission, contaminated water, and contaminated food, prevention methods should address these causes. The risk of fecal-oral transmission of pathogens can be reduced by good hygiene, including washing hands eating utensils with warm soapy water on a timely basis. Additionally a three-bowl system can be used for washing eating utensils.

Treating water

Various filters and chemicals are available for treating drinking water.cite encyclopedia |last=Adachi |first=Javier A. |author= |authorlink= |coauthors=Howard D. Backer, and Herbert L. Dupont |editor=Paul S. Auerbach |encyclopedia=Wilderness Medicine |title=Infectious Diarrhea from Wilderness and Foreign Travel |url= |accessdate= |edition=5th ed. |publisher=Mosby |location=St. Louis |year=2007 |pages= |isbn=0-323-03228-1 |pages=1418 |quote= ] (see Portable water purification). Factors in choice may include the number of people involved, space and weight considerations, the quality of available water, personal taste and preferences, and fuel availability.

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.

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.cite journal |author=Backer H |title=Water disinfection for international and wilderness travelers |journal=Clin. Infect. Dis. |volume=34 |issue=3 |pages=355–64 |year=2002 |month=Feb |pmid=11774083 |doi= |url=http://www.journals.uchicago.edu/doi/full/10.1086/324747?cookieSet=1]

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. [harvard citation|Backer|2007|Ref=none |p=1411]

The backcountry medical text "Wilderness Medicine," describes water disinfection and personal hygiene as one key to preventing wilderness diarrhea. Drinking untreated backcountry water is "like Russian roulette," according to its editor, Paul S. Auerbach, in an interview with REI.com. Auerbach added that while research has shown "Giardia" in wilderness water sources is "probably not as prevalent as once believed...it's still present". Howard Backer, author of "Wilderness Medicine's" guidelines on water disinfection, told the same publication that if a wilderness visitor is confident of untainted alpine water, "you're probably safe to drink it untreated," but that in areas with significant human or animal activity, the risk of infection makes precautionary disinfection a wise precaution. [cite web |url=http://www.rei.com/expertadvice/articles/water+risks.html |title=Expert Advice: Water: What Are the Risks? from REI |format= |work= |accessdate=] .

"Giardia lamblia" 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" may survive in cold waters (4°C) for up to 18 months, and can even withstand freezing, although its viability is thereby greatly reduced. Citation| first= | last=Prepared by Federal-Provincial-Territorial Committee on Drinking Water of the Federal-Provincial-Territorial Committee on Health and the Environment (2004)| coauthors=| contribution=Protozoa: Giardia and Cryptosporidium| title=Guidelines for Canadian Drinking Water Quality: Supporting Documentation| editor-first=| editor-last=| coeditors=| publisher=Health Canada| place=| pages=| date=| year=2004| id= | contribution-url=http://www.hc-sc.gc.ca/ewh-semt/alt_formats/hecs-sesc/pdf/pubs/water-eau/protozoa/protozoa.pdf| format=| accessdate=2008-08-07 ] Many other varieties of diarrhea-causing organisms, including "Shigella" and "Salmonella typhi", and hepatitis A virus, can survive freezing for weeks to months.cite journal |author=Dickens DL, DuPont HL, Johnson PC |title=Survival of bacterial enteropathogens in the ice of popular drinks |journal=JAMA |volume=253 |issue=21 |pages=3141–3 |year=1985 |month=June |pmid=3889393 |doi= |url=] Virologists believe all surface water in the United States and Canada has has the potential to contain human viruses, which cause a wide range of illnesses including diarrhea, polio and meningitis.cite journal |author=Backer H |title=In search of the perfect water treatment method |journal=Wilderness Environ Med |volume=11 |issue=1 |pages=1–4 |year=2000 |pmid=10731899 |doi= |url=] cite book |author=Gerba C, Rose J |chapter=Viruses in Source and Drinking Water |editor=McFeters, Gordon A. ed.|title=Drinking water microbiology: progress and recent developments |publisher=Springer-Verlag |location=Berlin |year=1990 |pages=380–99 |isbn=0-387-97162-9 |oclc= |doi= |accessdate=] cite book |author=White, George W. |title=The handbook of chlorination and alternative disinfectants |publisher=Van Nostrand Reinhold |location=New York |year=1992 |edition=3rd edition |pages= |isbn=0-442-00693-4 |oclc= |doi= |accessdate=]

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.cite book |last=Adachi |first=Javier A. |author= |authorlink= |coauthors=Howard D. Backer, and Herbert L. Dupont |editor=Auerbach, Paul S. ed.|title=Wilderness Medicine |isbn=0-323-03228-1 |chapter=Chapter 62: Infectious Diarrhea from Wilderness and Foreign Travel|url= |accessdate= |edition=5th edition |date= |year=2007 |publisher=Mosby Elsevier |volume= |location=Philadelphia, PA |id= |doi= |pages=1418 |quote= ]

One researcher, in discussing evidence for Giardia contamination of backountry water sources, suggested that if "Giardia lamblia" is an uncommon isolate and wilderness-acquired diarrhea is infrequent, then it may not be cost effective to recommend filtering for recreationalists involved in short-duration trips.

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. cite web|url=http://www.rei.com/expertadvice/articles/water+risks.html |title=Water: What Are the Risks? |accessdate=2008-08-07 |last=Wood |first=T. D. |date=2008 |work=REI.com ]

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.

Personal hygiene

The text "Medicine for Mountaineering and Other Wilderness Activities" Seattle, Washington: The Mountaineers Books, 5th edition, 2001] , also advises that disinfection and hygiene are necessary to avoid risk, although elsewhere, the same work notes that "exaggerated concern" has been raised about the issue.

Other commentators place relatively greater emphasis on preventative hygiene. Thomas R. Welch in a 2004 editorial in the journal "Wilderness Medicine" expressed the view that "stopping hand-to-mounth spread is the key to preventing gastrointestinal infection" and that routine universal treatment of water should be de-emphasized. [ [http://www.wemjournal.org/pdfserv/i1080-6032-015-04-0235.pdf] ] Careful attention to personal hygiene can help prevent the spread of infection.

Other measures

Also, one study suggests that on very long trips, taking multivitamins may reduce its incidence. WD.

Epidemiology

The risk of acquiring infectious diarrhea in the wilderness arises from inadvertent ingestion of pathogens. Various studies have sought to estimate diarrhea rates among wilderness travelers and results have ranged widely. A number of these have either focused on only one pathogen, Giardia lamblia, or provided scant data.

The rate of diarrhea varies dramatically between studies and may depend on the time of year, the location of the study, the length of time the hikers were in the wilderness, and the study methodology.

Surveys among hikers who completed the Appalachian Trail reported more than half experienced at least one episode of diarrhea, usually of two days or less in duration. [ [http://findarticles.com/p/articles/mi_m0689/is_n5_v36/ai_13928819/pg_3?tag=artBody;col1] ] cite journal |author=Boulware DR, Forgey WW, Martin WJ 2nd |title=Medical Risks of Wilderness Hiking |journal=Am J Med |volume=114 |issue=4 |pages=288–93 |year=2003 |pmid=12681456 |doi= ] cite journal |author=Boulware DR |title=Influence of Hygiene on Gastrointestinal Illness Among Wilderness Backpackers |journal=J Travel Med |volume=11 |issue=1 |pages=27–33 |year=2004 |pmid=14769284 |doi= ] Treating water and routinely washing hands with soap and water after defecation reduced the incidence.

Of backpackers who completed the Long Trail in Vermont, gastrointestinal complaints were reported by 10.7% of through-hikers who completed the trail in an average of 25 days, compared to 3.8% of section hikers reported. [ [http://www.wemjournal.org/pdfserv/i1080-6032-013-02-0131.pdf] ]

Giardia was found in 5.7% in stool samples of 41 backpackers in California's Sierra Nevada in 1993 but none were symptomatic. [cite journal |author=Zell SC, Sorenson SK |title=Cyst acquisition rate for Giardia lamblia in backcountry travelers to Desolation Wilderness, Lake Tahoe |journal=Journal of Wilderness Medicine |year=1993 |volume=4 |issue=2 |pages=147–54 |url=http://www.wemjournal.org/pdfserv/i0953-9859-004-02-0147.pdf |format=PDF] 16.7% of subjects in this study developed mild gastrointestinal illness other than giardiasis. Water samples from three popular stream sites revealed cyst contaminations in the single digit range for every 100 gallons filtered; with ingestion of 10 cysts considered a minimum infective dose.

In 2000 a review of four separate field studies, concluded that the general rate of infectious diarrhea acquired in the wilderness "is probably less than 10%, with scant data placing it in the 3% to 5% range." [http://www.wemjournal.org/pdfserv/i0953-9859-003-03-0241.pdf.] Howard Backer, author of the water disinfection chapter of a standard reference work "Wilderness Medicine" agreed with "much of [this] risk analysis." and commented that "there is much misunderstanding, verging on paranoia, about the risk of acquiring diarrhea from microorganisms resident in wilderness water," and that fecal-oral transmission may be the most common vector for backcountry Giardia infection. Backer, however, disagreed with the review's suggestion that routine disinfection of water may be unwarranted during relatively brief backcountry visits. [ [http://www.wemjournal.org/pdfserv/i0953-9859-003-03-0237.pdf] ]

Among National Outdoor Leadership Schools participants in various wilderness settings (primarily in North America, but also in South America, Asia, and Australia), gastrointestinal illnesses occurred at rates of 0.44 per 1000 days in 1984-1989 and and 0.20 in 1999-2002. The rates in 2002-2005 of 0.26 rates per 1000 days comprised 23% of all illness reported in the programs. [ [http://www.nols.edu/resources/research/pdfs/medical_incidents_evacs.pdf] ]

A study at Grand Teton National Park, found 69% of diarrhea affected visitors had no identifiable cause, with 23% having Campylobacter and 8% Giardia; Campylobacter enteritis occurred most frequently in young adults who had hiked in wilderness areas and drunk untreated surface water in the week prior. [http://www.medscape.com/medline/abstract/6859722?src=emed_ckb_ref_0]

Backcountry water quality surveys

Other sampling surveys have focused on micro-organism content of backcountry water in California's Sierra Nevada.

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. Ingesting 10 Giardia cysts is regarded in the minimum infective dose. 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.Fact|date=October 2008

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. [ [http://www.yosemite.org/naturenotes/Giardia.htm] ]

A further survey of 23 sites in the Sierra Nevada in 2003 sought to mesure coliform bacteria, used as indicators of fecal pollution. Coliforms were detected at eight of the sites. [http://sierranevadawild.gov/features/water-is-it-safe-to-drink] . Very low levels were measured in six of eight sites. Two sites had moderate levels. Author Robert Derlet of the University of California Davis medical school expressed the view that "bacteria, and not protozoa such as Giardia, pose a greater risk of causing water-borne disease in humans."

Derlet performed a similar survey in 2007 of 37 sites in Kings Canyon and Sequoia national parks and found coliforms at 14 sites. None of the 11 sites classified as wild areas had coliforms; two of 12 sites classified as backpack and day-hike areas had coliforms and 12 of 14 sites classified as pack animal areas had coliforms. [http://www.yosemite.org/naturenotes/Derlet_Water_SEKI_2007.htm] Data by risk category was consistent with prior studies in the immediate region, as well as data from the entire Sierra consisting of nearly 600 samples analyzed by Derlet from 2001-2007. Elsewhere, the author expresses the view that the risk of giardiasis from backcountry water has been "well over-stated." [http://www.yosemite.org/naturenotes/DerletWater.htm] and that "perhaps less than 1% of streams in the Sierra would have Giardia significant enough to cause infection in humans."

However, almost all of these backcountry water quality surveys did not address the issue of transient contamination. For example, the likely model for the risk of Giardia from wilderness water is pulse contamination, that is, a brief period of high cyst concentration from fecal contamination. [harvard citation|Backer|2007|Ref=none|p=1372]

Other studies

In 2000 a North America literature review found a high incidence of confirmed giardiasis among outdoor recreationalists, but little association between drinking backcountry water and acquiring giardiasis. [cite journal |author=Welch TP |title=Risk of giardiasis from consumption of wilderness water in North America: a systematic review of epidemiologic data |journal=Int. J. Infect. Dis. |volume=4 |issue=2 |pages=100–3 |year=2000 |pmid=10737847 |doi= |url=]

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. cite journal |author=Welch TR, Welch TP |title=Giardiasis as a threat to backpackers in the United States: a survey of state health departments |journal=Wilderness Environ Med |volume=6 |issue=2 |pages=162–6 |year=1995 |month=May |pmid=11995903 |doi= |url=]

ee also

* Wilderness medicine

References

*

Footnotes