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M. Doherty M_Doherty at NIH.gov
Mon Aug 14 10:15:29 EST 1995

In article <40fup7$oc7 at newsbf02.news.aol.com>, peterhn at aol.com (PeterHN) wrote:

> Much time and trouble is spent taking precautions to avoid water-born
> giardiasis by recreational campers/hikers. My experience is in the Sierra
> Nevada Mountains in California, where water is supposed to be filtered or
> boiled for five minutes before drinking. Is there any information
> available on the actual incidence or prevalence of giardia in thia area? 
> PeterHN at AOL.com

It varies by area.  Heavily used areas such as the Desolation wilderness
(especially the lower reaches) near Tahoe had relatively high number of
positives in a sampling test done a few years ago.  However, remoteness is
no guarantee of purity.  A friend contracted giardiasis from drinking
water in the Dinky Lakes area, a long way from the trailhead - and this
was close to its source as snow melt.  Giardia cysts will survive at some
period frozen, and the source in this case is likely to be wild animals
(or those goddamn cows).

As a big fan of Sierra hiking, I know what a pain it is to filter all your
water, but having also seen the effect of Giardiasis, I would never
consider a hike without my pump.  

I know this doesn't answer your question as to incidence, but even if the
odds are 100 to 1, it won't take too long to strike out.

Cheers, Mark

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