[pct-l] Why Rockwell is largely wrong on Giardia

[Bruce 'Buck' Nelson]

Ken,

No need to insinuate that I'm a liar even if you disagree with me.

This statement of Rockwell seems pretty clear to me: "One conclusion
of this paper is that you can indeed contract giardiasis on visits to
the high mountains of the Sierra Nevada, but it almost certainly won’t
be from the water. So drink freely and confidently."  I have shown his
calculations of the odds of contracting Giardiasis are deeply flawed
due to a misinterpretation of a single very limited study.

You say:  "He states that he thinks that it is not water, but poor
hygiene among hikers.  I can testify to that!"

Many Giardia experts, including at least some physicians around the
Sierras that routinely treat PCT hikers, believe backpackers are
getting Giardia from the water. You ignored the large study I cited,
as well as the large poll I linked to. Both show the rate of infection
is triple for outdoors people that don't treat water and to me they
carry a lot more weight than any individual's opinion, including yours
or mine, or Rockwell's speculation about what is causing Giardiasis in
the Sierras. And it is speculation.

You said "Your rather disingenuous mention of municipal water supplies
borders on an outright lie.  He was SPECIFICALLY talking about the
water supply of San Francisco, which was NOT treated." Mighty strong
words. And you are flat wrong. On both counts. Rockwell talks about
San Francisco's AND Los Angeles's water supply, both of which are
treated. At the time Rockwell wrote his paper the Hetch Hetchy water
supply HAD been given a waver for FILTERING but still had to comply
with DISINFECTION standards (using Chlorine.) Thus, Rockwell seems a
bit disingenuous, if you will, for saying "the California Department
of Health Services have granted Hetch Hetchy water a filtration
exemption, meaning that filtration treatment to ensure its safety from
Giardia and other organisms is not required." It would be like saying
I never filter my water while not telling you I treat my water with
Aqua Mira. Don't you think? My point on the relative concentration of
Giardia cysts near the source is also valid.

If you read through my blog post you'll find I've cited considerably
more scientific sources than you did. I “cherry-picked” the part about
drinking water because that was the topic.

You said: "You have misinformation in your post.  For example, you say:
'The incubation period of Giardia is usually 3 to 25 days or longer.' "

>From the EPA: "The incubation period (time interval between ingestion
and the first appearance of symptoms) can range from 3 to 25 days."
Many other sources agree. It’s important that people know that
symptoms can appear sooner than the oft-quoted 7-10 days.

One study from the Sierras that I cited had 35 people tested before
and after their trip. Two ended up with lab confirmed Giardiasis. A
third had the symptoms but came back negative. FWIW there was Giardia
found in many water samples although I don't think the true source of
infection was positively identified. Without that kind of testing I
KNOW people would have made the usual “they probably were carrying it
beforehand,” “they weren’t lab tested” arguments.

As I've pointed out elsewhere, there is a group of well known "giardia
skeptics" (Welch, Rockwell, Derlet) and it's no surprise they cite
each other. They largely contradict the CDC "(among those at greatest
risk are) backpackers or campers who drink untreated water from lakes
or rivers" and virtually every other organization addressing Giardia
and responsible for public health, including the Mayo Clinic. We can
both appeal to authority so it's necessary to sift through lots of
studies and expert opinion and come to rational conclusions of our
own.

You said "Odd that your somewhat dramatic incident did not get
recorded in your blog at the time....."

I don’t know, is it dramatic when you’re so sick you have trouble
walking? Certainly you’re not insinuating I’m fibbing? From my website
journal on July 26: "I rarely get sick on the trail, I'm happy to say,
but I got a bug of some kind; bad food, bad water, flu or whatever,
and felt mighty lousy for a couple of days. I must have lost five
pounds, so I'm looking pretty lean right now." (I don't know about you
but I've been through plenty of situations where I understate things
to avoid worrying people back home.) Right after I wrote that I got
extremely sick again. Luckily I was in Mammoth at the time and could
seek medical help. As a confirmed Giardiasis veteran I recognized the
symptoms and so did my Doc. One reason I knew what it was was that it
came back again with a vengeance after a lapse of several days, with
the sulphur burps and the other classic Giardiasis symptoms which I'd
just as soon forget. I trust my Doc and my own experience over the
speculation of anyone that wasn't there.

Unless the three doctors I cited are all lying, they treat lots of
cases of Giardiasis and don't report them. My Doc said he didn't know
of any of his colleagues that report it either. If they fail to report
it, many others also fail to report it as well, legally mandated or
not.

I am reasonably confident that Giardiasis was out of my system since
the last incidence was 25 years ago, I hadn't been sick with similar
symptoms since, and I took the full regime of medicine each time. This
was the first time in all those years I hadn't treated water. I was
hiking alone, southbound, at the time.

You said “Notice that the NUMBER ONE THING they recommend is good
hygiene, which you don't even mention.” How about when I said this in
my first post. “The NOLS policy of good hygiene and treating all water
has been very successful and seems sensible to me.” Does that count?
The part where I mentioned good hygiene first? : )

I don't consider my concerns about Giardia to be "hype" and "hysteria"
having had it three times. At this point I will continue to treat
water even if Hippocrates himself appears and tells me it isn't
necessary. I know dozens of people who’ve gotten Giardia in the
outdoors, many more than once, and nobody that has been attacked by
sharks.

I don't care if other people don't treat their water. It’s a dangerous
world with a lot of risk assessment to be done.  I DO care if people
advising the public understate the risk and consequences of infection.

http://bucktrack.blogspot.com/2011/03/waterborne-giardia-for-backpackers-no.html