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Medicine for the Outdoors

Dr. Paul Auerbach is the world's leading outdoor health expert. His blog offers tips on outdoor safety and advice on how to handle wilderness emergencies.

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Wilderness Water

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This is the next post based upon a presentation given at the Wilderness Medical Society Annual Meeting held in Snowmass, Colorado from July 24-29, 2009. The presentation was entitled “Wilderness Water: From Lowland Jungles to High Elevation Mountains.” It was delivered by one of the gurus of wilderness water – Robert W. Derlet, MD, who is a Professor in the School of Medicine at the University of California, Davis.

Water-borne diseases are not trivial. In the jungle, these include schistosomiasis (bilharzia), dracunculiasis (Guinea worm), amebiasis, microsporidiosis, cholera, salmonellosis, (e.g., typhoid fever) and polio. In other settings, they include traveler’s diarrhea from multiple causes, such as Escherichia coli (E. coli), Campylobacter species, Vibrio species, noroviruses and rotavirus. In addition, there is the backpacker’s affliction of “beaver fever,” or giardiasis, leptospirosis, algae, and other viruses.

Bob is a strong advocate that upstream activity (e.g., human settlements, farms, cattle and other livestock presence) in natural sources of water (e.g., streams, rivers, lakes) establishes the risk present in downstream water. From a microbiological risk perspective, the bottom sediment is worst, while the top six inches of water near a lake outlet pose the lowest risk. He is an expert on the epidemiology and risk factors for Giardia infection in the Sierra Nevada, California. Due to his excellent research, we know that cattle are the major importer of Giardia, that 3 to 5% of pack animals can be presumed to be infected, and that in the main, it takes 600 gallons of pooled Sierra water to find 10 Giardia cysts, so that the presence of this pathogen is not as common as usually believed. However, in certain watersheds, it remains prudent to filter and/or to otherwise disinfect drinking water collected from natural sources. As is the situation in many wilderness settings when precautions are the topic, it is wise and necessary to know the experience with the specific problem in the geography in question. With many nontoxic methods for water filtration and disinfection, a margin of error for safety does not pose significant time or expense constraints. It may, however, alter the taste of mountain water, so if that is your chief concern, you will have to make a choice.

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About the Author

Dr. Paul S. Auerbach is the world’s leading authority on wilderness medicine.

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