Wednesday, June 3, 2009

Water Treatment -- Giardia

If you haven't had Giardia, great. If you have, you know it isn't fun. While hiking the PCT in 1998, I lost maybe fifteen pounds, couldn't stand up straight from cramp and gas, couldn't eat, etc. I could never figure out what happened as I had treated with iodine. Then last week, after a few weekends of hiking the lower elevations of the Colorado Trail, it happened again. Same symptoms -- yuck. This time around, I had trouble finding a doctor who understood backcountry travel and it took some time to get it treated.

What happend? Maybe my toddler passed something to me, bad food, etc. Who can say? My research into backcountry water treatment, however, has caused me to change my approach.

The Centers for Disease Control and Prevention considers iodine or clorine to have a "low to moderate effectiveness" in killing Giardia. The CDC considers clorine dioxide (KlearWater/Portable Agua) as having a "high effectiveness" in killing Giardia. For Cryptosporidium, the CDC considers iodine as "not effective" and clorine dioxide as having a "low to moderate effectiveness." The CDC notes filtration is not effective in removing viruses. Doctors disagree on the prevalence of Giardia, especially in alpine areas, but generally agree the threat is greater at lower altitudes and in higher impact areas.

Surfing the various hiker sites, you find a lot of people who recommend just drinking out of the stream. This approach certainly works for some people -- a significant portion of the population doesn't show symptoms for Giardia, Crypto, etc. This approach also seems to work well in alpine areas.

My conclusions:

1. Some people don't seem affected by Giardia and therefore don't need to treat water;

2. Iodine and chlorine are at least somewhat ineffective for preventing Giardia and Crypto infestations at low altitudes or in areas with grazing;

3. Iodine and chlorine are at least partially unnecessary for preventing Giardia and Crypto infestations in alpine areas or in areas without grazing;

4. Filtering is better for Giardia and Crypto, but don't help with viruses.

For several years, I have used iodine exclusively for treating water. As most of my trips are in alpine areas, I most likely wasting my time (but certainly preventing a goiter).

My approach at this point will be to filter and use clorine dioxide. For longer hikes, and after the memory of evil gassy bloating fades, perhaps I will use just the filter. This is very much a "hike your own hike" subject; again, many people seem to be just fine drinking out of the stream.

Overall, I was somewhat surprised at what I learned. There seems to be at least a partial consensus in the lightweight hiking/climbing community that ditching the filter is an easy way to save a pound. I certainly thought so.

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