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Why Rockwell is Wrong about Giardia

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Re: Why Rockwell is Wrong about Giardia

Postby RoguePhotonic » Thu Feb 21, 2013 10:26 pm

Any speculation on why a doctor would lie if they did would just be counter productive.

Now we might be able to narrow it down when you say the PCT hikers come through and have it. Is it only the PCT hikers or is there a large amount of other general backpackers? You might be able to narrow it down where they are getting it. Probably some where in the Southern Sierra where there are allot of cows.



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Re: Why Rockwell is Wrong about Giardia

Postby dave54 » Thu Feb 21, 2013 10:45 pm

Some time ago I read several papers on giardia in mountain areas (do not recall the specific papers), but I remember one significant (to me) thing when I reviewed the methodology of the studies.

The papers that claimed low concentrations in the water samples were taken in the early summer, where the samples that showed higher concentrations were taken in the late summer to fall. This is entirely logical to me. Early summer would have higher flows of colder and cleaner water from fresh snowmelt. Later in the summer/fall water flows would be warmer, slower, and exposed to the elements/contamination for several months. None of the papers addressed the seasonality of the sampling and how that could effect the results.

If anyone in the research field is reading this a new opportunity for a study is presented: take samples from the same point in a stream over the course of a year and compare the sample results.

I also recall a study on water quality in Oregon, and E.coli. Where cattle had grazed the E. coli was higher, as expected. But additional research showed the E.coli was predominantly a human strain, not bovine. :eek:
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Re: Why Rockwell is Wrong about Giardia

Postby chrisdiercks » Fri Feb 22, 2013 7:37 am

Dave 54, if you could find the reference to that study I would be interested in looking it up. Another logical factor in the seasonality of concentrations is the exposure to more people/ livestock and animals after the snow melts combined with less flushing.

I freely admit that I don't get on to this site very often so let me introduce myself. My name should be obvious (Chris) and my background is in geology, ground water hydrology, and groundwater geochemistry. Basically I spent 9 years working contaminated sites with some ground water resource work thrown in off and on. I have been rambling in the Sierra Nevada for 45 years and was taught by my dad how to pick water for drinking. Around 1985 I started treating water when I went up with newbies. What I do now depends upon what I am doing and where I am going. Never been sick...so I guess I am one of those who are immune???

I've spent a little time looking at Coulter's postings at other forums and sites. He's been at this for at least 2 years now and it does seem like he is mostly interested in understanding the problem. The information on this topic has not been summarized well (to my knowledge at least) and there seems to be a distinct lack of data on the topic. I will try to go through what I can again as its been awhile and see if anything new can said; It will take a while, I mean there are 4 threads just on this site alone and a LOT of second and third hand info. I'll at least PM Coulter as I do have some problems with some of his conclusions as written. About Rockwell? well I need to re read the thing but he was somewhat clueless about the surface layer of the lake being safe. In a totally stagnant lake the UV light may be enough to kill what's there, but wind (common in the Sierra) causes upwelling and turnover is common in most if not all lakes as soon as the ice melts.

Bottom line though, each person needs to assess risk for themselves in all things in the backcountry, not just in the Sierra which is one of the "safest" ranges out there. I know what I need to do when I am out there for water and that is what matters. If I'm worried about somebody else, I treat. Simple.
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Re: Why Rockwell is Wrong about Giardia

Postby Colter » Fri Feb 22, 2013 8:47 am

RoguePhotonic, it's mostly non-thru-hikers getting giardia just because there are so many more of them. There does seem to be a spike in PCT thru-hiker giardia reports from the Kennedy Meadows area through the Sierra. I think the infection rate is relatively high with thru-hikers though. The infective dose is cumulative to a degree, http://www.waterbornepathogens.org/inde ... &Itemid=72 (click on infective dose) and of course thru-hikers tend to be exposed to more natural water sources.

Good stuff dave54, The CDC consistently reports a spike in reported cases at certain times of year: The number of cases peaked annually during early summer through early fall. http://www.cdc.gov/mmwr/preview/mmwrhtml/ss6105a2.htm It's been found that heavy rains often flush large amounts of contaminants into surface waters.

chrisdiercks

You said: Another logical factor in the seasonality of concentrations is the exposure to more people/ livestock and animals after the snow melts combined with less flushing. I think the science backs you up on that.

I think it would be good to discuss the science of what I've written here if you disagree with my conclusions. An open discussion is a good thing as long as it's civil.

You might be immune, or lucky, or skillful, or a combination of the three. It's hard to predict the future based on the past, though.

I roamed Sierra from the early 70s to early 90s, never did a thing to a water, anywhere.

The first time I cought the bug, I was told it was just a fluke. I lost about 10 pounds after drinking a bit of water from snow on Dana Plateau. The second time, I drank a little from a trickle after climbing the north ridge of Teewinot in the Tetons. Another horrific experience, pounds lost, that horrible Flagil etc...
http://www.summitpost.org/phpBB3/water- ... 64320.html
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Re: Why Rockwell is Wrong about Giardia

Postby RoguePhotonic » Fri Feb 22, 2013 9:10 am

I still have doubts. I simply need more data. What your saying with this doctor in Mammoth goes against everything I know or have experienced on the subject.

When pointing to the Southern Sierra you have to trace back in time. If it takes weeks for Giardia to make you sick after you picked it up then the average PCT hiker has covered hundreds of miles by the time they wander off the trail to find a doctor.
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Re: Why Rockwell is Wrong about Giardia

Postby Colter » Fri Feb 22, 2013 9:47 am

RoguePhotonic wrote:...If it takes weeks for Giardia to make you sick after you picked it up then the average PCT hiker has covered hundreds of miles by the time they wander off the trail to find a doctor.

But it doesn't take weeks.

Acute giardiasis develops after an incubation period of 1 to 14 days (average of 7 days) and usually lasts 1 to 3 weeks.

http://www.dpd.cdc.gov/dpdx/HTML/Frames ... _page2.htm

A mean incubation of about 9 days is often quoted, and it seems it's usually over 5 days and can be 25 days or more.

Mammoth is a little over 200 miles from Kennedy Meadows.
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Re: Why Rockwell is Wrong about Giardia

Postby balzaccom » Fri Feb 22, 2013 10:34 am

chrisdiercks wrote:Dave 54, if you could find the reference to that study I would be interested in looking it up. Another logical factor in the seasonality of concentrations is the exposure to more people/ livestock and animals after the snow melts combined with less flushing.

I freely admit that I don't get on to this site very often so let me introduce myself. My name should be obvious (Chris) and my background is in geology, ground water hydrology, and groundwater geochemistry. Basically I spent 9 years working contaminated sites with some ground water resource work thrown in off and on. I have been rambling in the Sierra Nevada for 45 years and was taught by my dad how to pick water for drinking. Around 1985 I started treating water when I went up with newbies. What I do now depends upon what I am doing and where I am going. Never been sick...so I guess I am one of those who are immune???

I've spent a little time looking at Coulter's postings at other forums and sites. He's been at this for at least 2 years now and it does seem like he is mostly interested in understanding the problem. The information on this topic has not been summarized well (to my knowledge at least) and there seems to be a distinct lack of data on the topic. I will try to go through what I can again as its been awhile and see if anything new can said; It will take a while, I mean there are 4 threads just on this site alone and a LOT of second and third hand info. I'll at least PM Coulter as I do have some problems with some of his conclusions as written. About Rockwell? well I need to re read the thing but he was somewhat clueless about the surface layer of the lake being safe. In a totally stagnant lake the UV light may be enough to kill what's there, but wind (common in the Sierra) causes upwelling and turnover is common in most if not all lakes as soon as the ice melts.

Bottom line though, each person needs to assess risk for themselves in all things in the backcountry, not just in the Sierra which is one of the "safest" ranges out there. I know what I need to do when I am out there for water and that is what matters. If I'm worried about somebody else, I treat. Simple.



This is a great post. Thanks, Chris!
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Re: Why Rockwell is Wrong about Giardia

Postby chrisdiercks » Fri Feb 22, 2013 11:28 am

Coulter,

Let me see if given my short amount of time to put into this, I can show you an example of my concerns with some of your analysis of this subject. In short, I am not arguing that giardia isn't a problem, rather, that I have issues with your view of certain "facts".

Process is critical to define and understand a problem. In another way to look at it, an experiment must be reproducible to have any real value in gaining a consensus in the scientific community. Very little work has been produced that attempts to fully understand the epidemiology of giardia. Here is a quote from the conclusion of this article you quoted above .

"Although giardiasis is the most common enteric parasitic infection in the United States, knowledge of its epidemiology is still lacking in public health research. The majority of data on giardiasis transmission comes from outbreak investigations; however, the overwhelming majority of reported giardiasis cases occur sporadically. "

Personally, the aforementioned CDC article (actually just a summary of the study) is well presented but to fully understand how good the analysis of the data are, you really need to see the data. But a major conclusion is that not enough study has been done to really understand the problem. This includes understanding the incubation period which may be a function of a whole slew of things. Exacerbating this is nature of the data collected, which for the most part has been pulled together after outbreaks have occurred. This means the doctors need to take a best guess as to when exposure occurred...and this is probably the least important thing on their mind while figuring out what to do for the patient.


RoguePhotonic wrote:...If it takes weeks for Giardia to make you sick after you picked it up then the average PCT hiker has covered hundreds of miles by the time they wander off the trail to find a doctor.


But it doesn't take weeks.

Acute giardiasis develops after an incubation period of 1 to 14 days (average of 7 days) and usually lasts 1 to 3 weeks.

http://www.dpd.cdc.gov/dpdx/HTML/Frames ... _page2.htm

A mean incubation of about 9 days is often quoted, and it seems it's usually over 5 days and can be 25 days or more.


That guidance doc you have referenced, those numbers are their best guess on the conservative side. Those numbers may be right, but they do not really know because the studies have not been done (as far as I can tell 'cause I have not kept up with this topic). And therefore, RoguePhotonic's numbers of a couple weeks incubation time are not all that far off. 14 days is a couple of weeks. An in shape hiker can cover nearly 300 miles in that amount of time. The point is that people can disagree about it, but the incubation time is not well understood. And until the proper studies are conducted it won't be and arguments like this will be very confusing to people. Sorry, but I am still struggling with time and presenting info properly here. I'll try to get back here this weekend.


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Re: Why Rockwell is Wrong about Giardia

Postby Colter » Fri Feb 22, 2013 1:29 pm

Hi Chris,

Thanks the response. What usually happens on threads like this is people tell their own anecdotes and then, as often as not, get angry with people whose anecdotes and risk assessments differ from their own. What I've tried to do is look beyond that to what the science has concluded from much larger data sets.

I'm not sure how the CDC's 9 day mean incubation time is "conservative." There would be no reason I can see to not get it as accurate as possible. We have to go by the best data we have, and the best data we have shows 9 days is "average." I think that's a more useful and accurate number than "weeks." The whole incubation time is only tangential regardless.

You said ...the Sierra which is one of the "safest" ranges out there. I'll apply the same standards to you. What study is that drawn from and did you study the underlying data? I suspect that statement isn't science based at all.

I also notice you didn't address any of the flaws in Rockwell's paper I identified in the original post.
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Re: Why Rockwell is Wrong about Giardia

Postby chrisdiercks » Fri Feb 22, 2013 2:59 pm

My biases; Looking at raw data and collections of data is pretty boring to most people and I am very hesitant to do much of that here. (picture one of those little yellow guys sleeping here) But there are certain standards that need to be met to have a reliable data base to evaluate and solve a problem. I'll grant you its been awhile for me, but I still know how this stuff is done. Look, I've written SOP's (standard operating procedures) for drilling, sampling in soil, water, groundwater, chain-of-custody, data analysis (including statistics), and sampling grid development for environmental and geophysical sampling, and followed that up with tons of field work. Be aware that I have worked with "thin" data sets (small clients with spills) and know how to build a statistically robust data set. I've even presented results to the US EPA. So I do have a biased outlook and it's based on my past experience.

I have no axe to grind one way or another; I readily accept the need for people to treat drinking water as well as those who trust themselves to "choose wisely". Heck, there are plenty of areas where I treat the water before I drink it.

Rockwells article; Well I did sort of address it. I said It"s been a while, I need to re read it. The only point I remember clearly is about the surface water of lakes which I addressed a couple of posts above. Frankly, I agree that Rockwells study is not that great and my response to it was that I pretty much I ignored it. It hasn't really affected me in a meaningful way so why should I bother. I'm still waiting for a REAL study to come out. And I admit when I say REAL it is given my aforementioned bias. If you have a link to one, I would love to see it.

I'm not sure how the CDC's 9 day mean incubation time is "conservative." There would be no reason I can see to not get it as accurate as possible. We have to go by the best data we have, and the best data we have shows 9 days is "average." I think that's a more useful and accurate number than "weeks." The whole incubation time is only tangential regardless.


On a fact sheet, they are stuck with producing guidance for public consumption. They are forced to come to a conclusion with a lack of data. I've been in a grossly similar circumstance before. Conservative is the only way to go, unless someone above them overrides their process. But also a fact sheet or guidance doc is not the same as a study. The easiest way to tell the difference is to look at the references. The CDC guidance doc basically has none, and the CDC study has a huge laundry list of ref's. And that study looks pretty solid to me given the cursery look I've had at it. And what's funny is the language in the conclusion screams this topic needs a lot more study. You will not see that in a guidance doc as it's supposed to give confidence to the public that "we know what's going on here". The other part of the whole equation is the politics, right? You may think it's not there, but it is.

Oh yea, tangential or not, the incubation was only one example of how you seem to not really fully understanding what the data mean. First you quote an average of 7 days, and then say " A mean incubation of about 9 days is often quoted, and it seems it's usually over 5 days and can be 25 days or more". I can't really tell, but this does suggest that you are starting to grasp the problem. An incubation range of 1 to 25 days? That is a data nightmare given all the possible variables that are unknown at this time. And that is just the incubation we are talking about.

You said ...the Sierra which is one of the "safest" ranges out there. I'll apply the same standards to you. What study is that drawn from and did you study the underlying data? I suspect that statement isn't science based at all.


You are right about that. It's just based on observations and personal experience in the Sierra and numerous other mountain ranges. But that is just really an aside alluding to regions with moose, larger black bear, brown bear, and harsher mountain weather like Montana, British Columbia, and Alaska. The point I was really making there was that we all make multiple risk assessments dependent upon the area we are heading into a particular region. It's not just about drinking water which is an easy fix. If you are worried about the water, bring treatment. If you are worried about brown bear, well you need to get multiple stratigies worked out for different situations. You know what I mean. The one problem is a slam dunk and the other is never 100%.

Coulter, it will probably be a few days before I am back (finally got the plumbing fixed!!!) I'll try to spend some time on this between now and them.

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Re: Why Rockwell is Wrong about Giardia

Postby Colter » Fri Feb 22, 2013 4:16 pm

Hi Chris,

It was classy of you to concede that one point. On forums most people would never do that.

You and I are deep in the weeds of rhetoric now. It would be great if you'd read Rockwell and my original post and tell us what you think.

Thanks!

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Re: Why Rockwell is Wrong about Giardia

Postby RoguePhotonic » Fri Feb 22, 2013 8:34 pm

This whole subject is not something I have gone into much depth on so that is why I do not get involved in a more detailed discussion on the data at hand. In this case I just go on what I know from my own experience and what I have learned from the great many Sierra hikers that I have talked with on their experiences.

Generally most people filter which is the end of the story. They filter so they don't have anything to add on the subject. Then 9 out of 10 people that don't filter will tell you they have never had a problem. The ones that do say they got sick cannot give any specific details that is of much use either which is understandable but ultimately puts doubt all around. At least that has been my experience out there. That is why when I hear about people coming in a couple times a week all summer in Mammoth with Giardia I find it hard to believe.
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