W o l r i e c l a b o u t g i a r d i a s i s ,t h e F o r e s r
mends treating or filtering water as a pre-
Service ancl National Park Service encour-
c a u t i o n , e s p e c i a l l yf o r i n e x p e r i e n c e dh i k -
age Sierfa l-rikersto either filter or treat
ers and campers Recent studies indicate
p e a k i n a g e - s p e c i f icca s er e p o r t s c o i n c i d e s
t h e i r w a t e r b e c a u s ei t c o u l d b e u n s a f e t o
that giardia incidence is extremell, low in
w i t h t h e s u m m e r r e c r e a t i o n aw
l a t e rs e a s o n
d r i n k G i a r d i a s i si s c a u s e db y t h e i n t e s t i n a l
the wilderness of Yosemite, Sequoia and
and might reflect the heavy use by young
parasite,Giardia lamblia. Accordingto the
K i n g s C a n y o n , B u t B o i a n o c a u t i o n s ," W e
children of communal swimming venues,"
National Institutesfor Hcalth (NIH), it's
can't say definitively that there's no giardia
the CDCreport stated
t r a n s n r i t t e ct lh r o u g h c o n t a c t w i t h i n f e c t e d
a n y w h e r eb e c a u s et h e w h o l e S i e r r ah a s n ' t
f e c e s ,e i t h e r d i r e c t l v( s u c ha s b e t w e e nc h i l -
b e e n s a m p l e d"
dren) or indirecth',tl.rroughfood and water
Giardiasis isn't a nationally notifiable
contamrnated with c_vst-containingfeces
disease. Still, the Centers for Disease
(see sidebar) Children, especially dia-
be carrying giardia with children being the
most likely to be infected. "The seasonal
F o r S i e r r ah i k e r s , t h e m o s t i n t e r e s t i n g
part of the CDC report is that during the
s t u d y p e r i o d a b s o l u t e l ln, o c a s e so f g i a r d i a sis were reported from California.
Control (CDC) reported that between 7979-
There are several factors working
pered children and toddlers being toilet-
1988, giardia caused an estimated4,600
against establishing viable populations of
trained, and families with young children
hospitalizations per year throughout the
giardia in the High Sierra. Trophozoites
who attend day-carecenters shoulder the
entire United States,The CDC also report-
can't survive outside of the host Giardia
greatestrisk of developing giardiasis,
ed giardia frequency increased between
cvsts cannot remain viable more than 2-3
Danny Boiano, aquatic ecologist for
1992-1997with 43 statesnow feporting the
m o n t h s i n f r c e z i n g r e m p e r a t u r e sC y s t s
Sequoia and Kings Canyon National Parks
says, "There's no evidence that the water
parasite. New York, with 3,673 cases in
I99 t-,had the highest incidence
encasedin snow or frozen lakes probablv
in the parks is unsafe." The NPS recom-
Some 7% of Americansare suspectedto
remain encasedin feces on, or under the
. l F R R A rE- R
l T A G E , M o v / J u n e2 0 0 4
d o n ' t l a s t r h e w i n t e r , C y s r sL h a t m i g h t
I
Allhough the Foresl Service ond Nofionol pork
Service soy there is no evidence of unsofe
woler, they recommend fillering or treoting
woler os o precoution (inser, this poge)
Author, Peter Stekel, o Sierrq hiker since
1965, sfill rorries woler lreqlment ond o filter,
but hqs olso leqrned to,,Drink Smqrl".
,'t
l,i
compared to what could be done without
any restriction and monitoring,,' Derlet
says. "In many wilderness areas of
Californiawhere there are cattle and sheep
grazing," pathogenic forms of e.coli are
common.
But how to explain the known incidence of diarrhea in Sierra hikers?
If it's from giardia, the affected person
has a greater chance of having picked it up
another member of their party.
from
Remember,it's commonly spread by direct
fecal-oral or food-borne transmission. The
same could be said for bacterial contami_
nation. Poor personal hygiene is a more
likely causefor most hiker diarrhea.
Avoiding giardia or pathogenic bacteria
from possibly contaminated water is easy,
but problematic. Water treatments relying
on iodine or chlorine have been found by
the CDC to be less effective than fikers
becausethey're highly dependent on water
temperature, pH and cloudiness,V,raterfil_
ters may remove giardia but not all
soil surface, will probably not survive the
winter's sub-freezingtemperatureseither.
mals. Human pathogens with potential
medical importance are present but have a
Though giardia is known to infecr
domestic and wild animals (cats,dogs, cat_
tle, deer, bear, rodents and beavers) no
low prevalence," Derlet says. Bacterial
pathogens were found in two specimens
(of 23) collected from wild animals while
evidence exists for its spread in the back_
country by packstock,During the summer
giardia was identified in one pack animal
sample near Tuolumne Meadows.
of 2003,Bob Derlet, MD, professor of medicine from the University of California at
Davis, hiked i85 miles between yosemite
and Sequoia National park collecting sam_
Derlet believesthe seriousnessof being
exposed to giardia in national park wilder_
ness has been over emphasized.,,Theaver_
age concentfation ofless than ten cystsper
1000 liters reported in studies of Sierra
ples of "road apples" to addressthe poten_
tial health risks to people drinking from
Sierra streams.
Nevada wilderness water poses minimal
risk to humans." That's a frequency lower
Dr Derlet found encouraging news for
both packers and backcountry hikers.
"Pack animal manure commonly encoun_
tered by backpackers on Sierra Nevada
than what is allowable in San Francisco and
Los Angeles, both of which import vast
trails contains large numbers of commen_
sal enteric bacteria normally found in ani-
the park serviceis doing a wonderful job of
preserving the backcountry, especially
amounts of Sierrawater for municipal use
"Iow pathogen numbers tells me that
pathogens. Easily clogged wirh sediments,
filters aren't suited for extended trips.
If concerned with water quality the best
advice appears to be learning how to
"Drink Smart." Get water from large fast_
flowing streamsor at lake inlets Since giardia cysts don't survive Sierra winters, any
contamination begins fresh every year.
Spring runoff therefore is safer than sum_
mer or fall. And so is water at higher eleva_
tions where reduced human and animal
presencemeans less opportunity for cont_
amination. Finally, avoid water passing
through heavily human or animal impacted
areas.Boiling water for severalminutes is
an tnconvenient option, using lots of fuel
which has to be carried. The best ^way to
avoid getting sick while hiking is to do
what your mother always told you: ,,Wash
your hands." sx
S I E R R A H E R j T A G EM, o y/ J u n e 2 O o 4