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Why Rockwell is Wrong about Giardia

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Re: Why Rockwell is Wrong about Giardia

Postby longri » Tue Feb 19, 2013 9:40 am

Colter wrote:
longri wrote:...I think it is a topic worth discussing...

This is a thread from Backpackinglight where I think everyone who was interested in the topic learned something. I know I did. It was a good exchange.
http://www.backpackinglight.com/cgi-bin ... 127.77.115

Thanks for that link, that was a really good discussion. It was impressive not only in that it shed a little bit of light on a subject lacking sufficient data but also in that it was so civil.

I'm not going to send you a PM and I don't need a reply to this, but have you attempted to contact Bob Rockwell and discuss the subject with him? A similar discussion took place online over ten years ago, one that you probably have found with google. It involved a backcountry enthusiast who was employed as a municipal water treatment professional. He had recently contracted giardiasis in the Sierra and took Rockwell to task. Bob's response was interesting to read.



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Re: Why Rockwell is Wrong about Giardia

Postby Colter » Tue Feb 19, 2013 10:51 am

Yup, that's the best thread I've seen on giardia. There was some real science there, and I too was impressed with the civility.

I have looked for current contact information for Rockwell but came up empty handed. I was debating a physician friend of his so perhaps Rockwell is no longer active on the topic.

I've likely read the thread that you're referring to, probably on http://www.whitneyzone.com where he used to post. Can you paraphrase what he said?

Here are a couple other posts I've written on the topic. I don't expect uninterested people to read them:
http://bucktrack.blogspot.com/2011/03/w ... rs-no.html
http://bucktrack.blogspot.com/2012/09/b ... cal_8.html

The latter you might find interesting, longri, because I think it shows that what is perhaps the second most cited "skeptic paper" is also riddled with misinformation.
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Re: Why Rockwell is Wrong about Giardia

Postby markskor » Tue Feb 19, 2013 11:31 am

Colter wrote:Here are a couple other posts I've written on the topic. I don't expect uninterested people to read them:

Colter,
That's the second snide remark you have made about members here in 7 posts (Talk to the hand). Nice way to start out.
Open discussion does not include being rude...IMHO, You are.
Mark
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Re: Why Rockwell is Wrong about Giardia

Postby Colter » Tue Feb 19, 2013 1:09 pm

markskor wrote:
Colter wrote:Here are a couple other posts I've written on the topic. I don't expect uninterested people to read them:

Colter,
That's the second snide remark you have made about members here in 7 posts (Talk to the hand). Nice way to start out.
Open discussion does not include being rude...IMHO, You are.
Mark

Hi Mark, I'm sorry if it came across that way. In both cases that surely wasn't my intention. Being snide is not a good way to make friends and influence people.

I think we can agree that it's easy to misinterpret tone when people aren't face to face and they don't know each other. I said "I don't expect uninterested people to read them" trying to be polite and not pushy, like handing a book to a friend and saying "I don't expect you to read it if you're not interested."

Similarly I said I will cease "talking to the hand" until when, and if, I detect some interest. :) I was offering to let the thread end and making fun of myself as the new guy (most people weren't interested in the topic and as stated several thought I was "late to the party") and not saying "talk to the hand" to the old salts here, that not being my place and would be both rude and foolish. I put the smiley face so people could read my intended tone.
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Re: Why Rockwell is Wrong about Giardia

Postby Maddog61 » Tue Feb 19, 2013 1:36 pm

Colter, I didn't take your comments as rude. In fact, I think you did a good job of remaining civil in spite of the less than warm response. I don't have enough experience on the topic to offer any constructive input, but as I wasn't present for the previous "beatings of the dead horse, " I have found this topic interesting. :-)
There are many members here that do not have decades of experience, yet many topics like this, (lightning safety, keeping down dry, weather etc.) are met with grumpy replies saying that this issue has been covered. I don't mean any offense to the grumpy people around here, :-) but perhaps if you're not interested in the debate, just ignore it.
I value these discussions, and know that I'll be more prepared on my few, short, precious trips to the Sierra this season. Besides, what else will we talk about while wishing we were up there?

Sent from my ADR6410LVW using Tapatalk 2
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Re: Why Rockwell is Wrong about Giardia

Postby Colter » Wed Feb 20, 2013 7:49 pm

Maddog61 wrote:Colter, I didn't take your comments as rude. In fact, I think you did a good job of remaining civil in spite of the less than warm response. I don't have enough experience on the topic to offer any constructive input, but as I wasn't present for the previous "beatings of the dead horse, " I have found this topic interesting. :-)
There are many members here that do not have decades of experience, yet many topics like this, (lightning safety, keeping down dry, weather etc.) are met with grumpy replies saying that this issue has been covered. I don't mean any offense to the grumpy people around here, :-) but perhaps if you're not interested in the debate, just ignore it.
I value these discussions, and know that I'll be more prepared on my few, short, precious trips to the Sierra this season. Besides, what else will we talk about while wishing we were up there?
Thanks for that, Maddog61!
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Re: Why Rockwell is Wrong about Giardia

Postby gdurkee » Thu Feb 21, 2013 1:40 pm

Interesting points re: Bob's article. It's worth noting that it was a literature review, summarized results and presented conclusions based on that. I talked to him fairly extensively about it after he first published it and I picked it up for Sierra Nature Notes. I thought it a very good effort and article on the subject and still think so.

That said it's, what?, 15 years old now. Definitely time for rethinking some of the conclusions presented. I'm also a little bothered that discussing stuff that appears previously is somehow an error in forum etiquette. Topics slide off the front page and are buried. New people come on board who could benefit from discussions held even a year ago. So on that point, I think a discussion or re-re-re discussion is worthwhile. The only thing I'd object to is obvious baiting or trolling, which is not the case here (though he edges close with the provocative -- and misleading -- title. Bob wasn't "wrong" -- it was a literature review. His conclusions from the existing studies and science were correct, certainly defensible).

There's no question that some people are incredibly susceptible to giardia -- the OP is an obvious example. As such, he should definitely treat everything. Obviously I talk to a lot of people who hike and have been doing so before and after water treatment became so widespread. In all those years -- probably over 10,000 people -- I've talked to only a handful of people diagnosed with giardia. No question it's nasty when you get it, but I'm not convinced it was ever that prevalent in the Sierra. There's not much difference in the number of people who have said they've had infections before or after the late 80s (?) when treatment became widespread.

I do think that simple hand washing among groups probably gets rid of a significant percentage of infections -- this is certainly the case in day care (cleaning toys etc. daily). But many mammals carry the cyst that can infect humans and so it's definitely in the water supply (belding ground squirrels have a very high infection rate, but it's not the same type that humans are susceptible to...)

But! Studies of cattle show a high percentage of cows carry the cysts -- especially calves. There's also a study from Yosemite that showed about 3 - 6% of horses out of Tuolumne carried giardia cysts (and about the same percentage carried Cryptosporidium parvum).

If I were a PCT hiker coming up through Kennedy Meadows, I would absolutely treat. Same going north through any USFS areas where cows are prevalent. But I also think there's very low risk for most people hiking in either Yosemite and Sequoia Kings. I carry a steri-pen now and do use it in high-use areas when I don't know of a side-stream or spring around.

g.
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Re: Why Rockwell is Wrong about Giardia

Postby Colter » Thu Feb 21, 2013 3:04 pm

Hi gdurkee,

Thanks for the sensible post. I agree with many of the things you said.

I do respectfully think though, that it's fair to say that Rockwell was "wrong" on many of the conclusions of the paper. And his paper, as you said, wasn't merely reporting the facts as known, he took certain facts and from those facts drew his own conclusions.

It's important to note that virtually every public health agency looked at much of the same science and drew often opposite conclusions. One side or the other has to be significantly wrong.

As you said There's no question that some people are incredibly susceptible to giardia -- the OP is an obvious example. As such, he should definitely treat everything. I certainly agree with you.

Rockwell says 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 personally don't think that's a defensible statement based on my personal experience AND an overwhelming amount of scientific data.

The most recent study of Sierra water was summarized like this:
Now, after 10 years of fieldwork and 4,500 miles of backpacking, Derlet knows for sure. What he has learned, after analyzing hundreds of samples dipped from backcountry lakes and streams, is that parts of the high Sierra are not nearly as pristine as they look.

Nowhere is the water dirtier, he discovered, than on U.S. Forest Service land, including wilderness areas, where beef cattle and commercial pack stock — horses and mules — graze during the summer. There, bacterial contamination was easily high enough to sicken hikers with Giardia, E. coli and other diseases


Read more here: http://www.modbee.com/2010/05/08/115893 ... rylink=cpy

Another of Rockwell's quoted statements "Neither health department surveillance nor the medical literature supports the widely held perception that giardiasis is a significant risk to backpackers in the United States" is also wrong and easily refuted and I believe I've done so on my blog posts linked above.

I actually did want to present some scientific facts and debate their meaning if people were inclined to do so. The points raised in the initial post were meant to be a good starting point.

And again, treating water or not is ultimately a personal decision and rational people can make different choices.

Thanks again!
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Re: Why Rockwell is Wrong about Giardia

Postby gdurkee » Thu Feb 21, 2013 5:37 pm

Wait, wait, wait there Dr. Science. Following up on the references, I think the problem is a bit overstated. I was worried about your statement:

I was able to find only two studies that tested hikers BEFORE and AFTER a trip to the field. They showed a minimum of 5.7% of hikers contracted Giardia in a single trip. Seems high, but it does show the risk can be very high at times. http://www.ncbi.nlm.nih.gov/pubmed/937629


It is high, but the reference is one specific incident in Utah where the authors couldn't figure out the source. As I said (and purely anecdotal yet worth something...) the Sierra, even in cattle areas, just doesn't get many cases of giardia.

Then there's:
His calculations on how many liters of water one would have to drink to get giardia in the Sierras are worse than useless. For one he uses water tests decades old. And he uses 10 cysts as the "infective dose." You will actually find the "10 cysts" repeated many places on the internet, but again, it's untrue. Experts have determined that there is a 2% chance of being infected by a single cyst. http://www.waterbornepathogens.org/inde ... &Itemid=38 The FDA says Ingestion of one or more cysts may cause disease. [Emphasis added]


Following up with that source you find that 2%/single cyst stuff is extrapolated and refers to infection (carrier) not symptoms:

Thus, although the individuals were infected, they did not have classical giardiasis.


Derlet (a friend) has done extensive testing for years. However, he's done very little testing for giardia. It's almost entirely e coli which he uses as an indicator of fecal contamination from all sources. There's a definite increasing correlation in e coli between pristine (no human or stock use), human use only and stock & human use.

There, bacterial contamination was easily high enough to sicken hikers with Giardia, E. coli and other diseases


That's what I indicated earlier, but even in yuckky cow areas, the symptomatic cases of either giardia or even intestinal grunge is not a major problem (there's definitely cases and some years they're significant). Derlet has not studied symptomatic outbreaks of disease in those areas. For sure the potential seems to be there but (and I'm very open to correction) the clinical cases aren't.

Whew. Maybe everyone else is right, this does get kinda whacked to death. But I guess my main point is not overstating or exaggerating the risk of giardia. We're slowly coming back to a reality-based attitude where people don't go thirsty because they've not treated the water or their pump broke or whatever. As you say, it's a personal choice, but should be one based on a realistic assessment of actual risk which, I maintain, is very low.

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Re: Why Rockwell is Wrong about Giardia

Postby longri » Thu Feb 21, 2013 6:30 pm

gdurkee wrote:I've talked to only a handful of people diagnosed with giardia. No question it's nasty when you get it, but I'm not convinced it was ever that prevalent in the Sierra.

I've had it (lab confirmed) and in my case it really wasn't that nasty. It went on for some time and I needed medication but I've had bouts of flu that were far more debilitating. I didn't get it in the Sierra though. And although I have no proof I think it did not come from the drinking water.


Colter wrote:...an overwhelming amount of scientific data.

Colter, that statement is clearly a gross exaggeration. If anything can be agreed upon it is that there is a dearth of solid data on this subject.

By the way, the water treatment professional I referred to before was Bruce Bindner. He and Bob had a brief exchange in rec.climbing about a decade ago. Bruce brought up the same point you made about how the EPA requirement for chlorination at that time had been designed in part to reduce viable Giardia cysts by 3-log. I'd read this ten years ago when it was first posted and then forgot about it. So that's old news in a sense although (with failing memories and new faces) it's worth revisiting.

Bruce also had a mild case. He went climbing again and did a first ascent on Castle Rock Spire within weeks of getting sick.
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Re: Why Rockwell is Wrong about Giardia

Postby Colter » Thu Feb 21, 2013 7:13 pm

gdurkee wrote:Wait, wait, wait there Dr. Science

It seems like that would qualify as snide. What do you think?

Your opinion
the Sierra, even in cattle areas, just doesn't get many cases of giardia.

vs a Sierra physician's experience

Several backpackers appear weekly at Centinela Mammoth Hospital in Mammoth Lakes sick enough with giardiasis to need urgent care
I know for sure what at least one more Sierra physician thought about the Rockwell paper when I asked. He laughed.

In that Colorado incident, they did determine it was from the water, Although the epidemiologic data and fecal coliform counts implicated the remote mountain stream used as water source by the group as the vehicle of transmission, Giardia lamblia cysts were not recovered from stream water. I researched this and found out that the type of test filter being used didn't work, so that's the expected result if there was giardia in the water.

There was a second study, too: http://download.journals.elsevierhealth ... 711729.pdf In that study, 2 of 35 people got Giardia, but were asymptomatic. A third had Giardia symptoms, was treated for Giardia, and quickly recovered. Giardia is often not detected with a single test. So it is certain at least 5.7% got Giardia, and it seems more than likely that 3 of 35 got Giardia, for a total of 8 1/2%. About 1/2 to 2/3 of the time people ARE asymptomatic, so that's no surprise.

You said Following up with that source you find that 2%/single cyst stuff is extrapolated and refers to infection (carrier) not symptoms Again, Rockwell did his risk calculations based on NO risk from 1-9 cysts. He is absolutely wrong on that and it significantly understates the risk, probably by more than an order of magnitude.The only study on infectious dose is the Rendtorff study. Different strains of giardia have dramatically different levels of infectivity. One thing I dug up is a quote from Rendtorff himself saying that they hadn't even determined if the cysts were viable. In other words, it's perfectly possible that ALL the men that didn't get giardia had no chance of getting it. The results HAVE to be extrapolated because the testing was so minimal. The only thing it determined for sure is that it proved the infectious dose is very low. To the best of my knowledge only five people in history have been tested below the ten cyst level, and that was one time with a single cyst each, a cyst that may have been dead to begin with.

Derlet's findings clearly refute Rockwell's drink freely and confidently.

Again the biggest retrospective study (what actually DID happen) ever done on the subject concluded drinking untreated mountain water is an important cause of endemic infection. http://www.journals.elsevierhealth.com/ ... 105_330%20

I talked to the experts at San Francisco Department of Public Health today about giardia in their water. They said the giardia counts were for raw water.

Here's how people are reading the Rockwell paper SanFrancisco water has more Giardia than Sierra...Hetch-Hetchy (One of San Francisco's Water Supply's) in not filtered at all. Except for the water treatment plant that Rockwell doesn't mention.

http://www.thebackpacker.com/trailtalk/ ... 380,-1.php
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Re: Why Rockwell is Wrong about Giardia

Postby rlown » Thu Feb 21, 2013 7:38 pm

at 1 degree F in Fairbanks, I can say that all Giardia cysts are dead.. same in the Sierra right now as they freeze and and die well above that temp. Maybe you're just bored and we have many other forum topics to fill in. History would be helpful, for instance.

What is your desire for this thread? If it was to inform, you're pretty much done, right?

This shouldn't be about CO or other places.. Just the Sierra. and we mostly know by now. HST has pointers to other threads sierra-related about water situations, and new people should see that blatant search capability at the top right of the page when logged in..

What more do you want?

Russ
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