From: tut@cairo.Eng.Sun.COM (Bill "Bill" Tuthill)
Newsgroups: rec.boats.paddle
Subject: Re: Giardia
Date: 16 Dec 1992 20:38:07 GMT
Organization: Sun Microsystems Inc., Mountain View, CA
NNTP-Posting-Host: cairo

dsj@juniper12.cray.com (Douglas Jackson) writes:
> 
> A friend of mine just called.  It seems he picked
> up Giardia(sp?).  He linked it to kayaking some
> of the rivers around Minnesota/Wisconsin.  Does
> anyone know anything about how common an ailment
> this is for whitewater paddlers? ...
> How widespread is the virus/bacteria?

Giardia is not a virus or bacteria, it is a protozoa.
Paddlers seem to get giardia both from drinking untreated
water from the river, and from swallowing water while on
a bad swim.  There is no excuse for swallowing water while
playing, just spit it out!

Here's my water filters panel from rec.backcountry.


Copyright (c) 1991 by Bill Tuthill

Unpurified drinking water may contain four things that pose health risks:
protozoan parasites (e.g. giardia), toxic bacteria, harmful viruses, and
poisonous chemicals.  Of the methods available in the field, only boiling
and iodine are entirely effective against the first three, and only charcoal
filtration is effective against the fourth.

The First Need(R) water filter is cheap (less than $40), but is effective
merely against protozoan parasites.  Its .4 micron filter pores are smaller
than giardia cysts at 3.5 microns, but larger than some bacteria, such as
E. coli at .3 to .9 microns.  The First Need's charcoal canister is not big
enough to be effective against poisonous chemicals -- you need a pound of
charcoal for this -- so it just adds unnecessary weight, and provides a
potential haven for the growth of harmful bacteria.  If you own a First Need
filter, flush it with iodine after each trip.

The Katadyn(R) water filter is expensive (over $200), but is completely
effective against bacteria as well as giardia.  Moreover, it can be cleaned
after it clogs up.  The Katadyn is effective at removing smaller bacteria
such as E. coli.  However, its .2 micron filter is not effective against
any virus.  If you travel abroad (to Nepal for example), you risk viral
infections such as Hepatitis A and Hepatitis non-A non-B, among others.

MSR and Pur have new water filter, which may be superior to the Katadyn.
Preliminary results from the field indicate that both filters may be
preferable to the Katadyn, although the MSR clogs up quickly and the Pur
leaves an iodine taste in the water.

To be entirely safe, water should be boiled for at least five minutes.
Giardia is killed in less than a minute at 176 degrees, well under the
boiling point.  Bacteria and viruses last somewhat longer, but are probably
killed in less than five minutes at 190 degrees.  Some viruses may last
longer; nobody knows.  At 10,000 feet water boils at 194 degrees; above
this altitude boil water about an extra minute for each 1000 feet.

If you have neither the time nor the inclination to boil water, iodine
is equally effective.  After 15 minutes (30 minutes for very cold water),
a sufficient dose of iodine kills all protozoa, bacteria, and viruses.
One readily-available choice is Potable-Aqua(R) tablets.  Dissolve one
tablet per liter of water (two tablets if cloudy) and wait.  The problem
with iodine tablets is that they degrade upon contact with moisture, so
keep that bottle dry, and discard it upon returning home.

Avoid halazone and Clorox, because chlorine is volatile, slow to disinfect,
and works differently against protozoa and viruses at various pH levels.
It also reacts with organic compounds to form carcinogenic chloramines.

Iodine is not highly toxic, and in fact is an essential ingredient of
human nutrition.  However, continuous ingestion of large doses may cause
health problems, so don't iodinate all your water for more than a few
months at a time.

The accepted concentration for iodine disinfection is 8 milligrams per
liter, but this is mostly to get rid of protozoan parasites.  A good way
to reduce overall iodine consumption and minimize that iodine flavor is
to filter first, then use a low concentration of iodine to get rid of
bacteria and viruses.  For this, a concentration of .5 mg/L is deemed
adequate, so one capful of PolarPure or one Potable-Aqua tablet should
disinfect around 16 liters of lightly filtered water.  The Timberline(R)
filter, with its 2 micron pores, is fine for removing protozoa.

Giardia has become a well-known, almost fashionable, outdoor hazard.
Many people who experience gastro-intestinal problems after drinking
bad water think they have contracted giardia.  In many cases they have
contracted something else.  Since the only FDA-approved treatment for
giardia (Flagyl) is very nasty, it's wise to make sure you really have
giardia before taking Flagyl.  Most low-grade bacterial infections go away
on their own, and Flagyl is ineffective against viral infections.  One
alternative to Flagyl is quinacrine.  In many parts of the world (Asia
for example) Tinidazole is available, and is preferable to Flagyl because
it is less toxic and quicker acting.

[This information based on "Medicine for Mountaineering", various owner's
pamphlets, and personal experience.]
Newsgroups: rec.boats.paddle