Forum Index » General Lightweight Backpacking Discussion » Giardia: Let's Talk SCIENCE


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Tom Kirchner
(ouzel) - MLife

Locale: Pacific Northwest/Sierra
Re: Some responses on 01/09/2014 20:29:51 MST Print View

"The EPA has said [Giardia]Cysts have been found all months of the year in surface waters from the Arctic to the tropics in even the most pristine of surface waters. Giardia cysts have been found in watersheds where the water looks perfect and where the watershed is classified as "pristine.""

Aside from this sounding like typical bureaucratic boiler plate, with no quantifying of distribution information, we keep coming back to that word "pristine". Care to give me your definition? IIRC, when you got giardia in the Sierra it presented about 7-8 days after you drank untreated water way down in the Kern Canyon, in an area heavily frequented by horse packers. South of Upper Funston Meadow? That area does not exactly meet my definition of pristine, which is very close to the dictionary definition: "Remaining in a pure state; uncorrupted by civilization" Aside from that, as I mentioned in my previous post, many High Sierra hikers drink untreated water year after year without ill effect. I guess we're all just lucky or asymptomatic?

Roger Caffin
(rcaffin) - BPL Staff - MLife

Locale: Wollemi & Kosciusko NPs, Europe
Re: Some responses on 01/09/2014 21:07:40 MST Print View

Hi Buck

Your argument is subject to a serious bit of creep.

On the one hand you have:
'Cysts have been found all months of the year in surface waters from the Arctic to the tropics in even the most pristine of surface waters.' (EPA) What this does not specify in any shape or form is how many cysts per litre. It could be 0.01 or less in some cases.

But you changed the meaning in a very serious manner when you followed the above with
'If giardia cysts are commonly found in backcountry water sources'
where I have added the emphasis to the word 'commonly'. There is no way you can get that word out of the EPA statement.

To me, the second statement has such a huge difference from the first that I will cry foul.

Fwiiw, I have had Giardiasis (twice), and my wife and I are very well aware of the risks. We avoid the water in certain areas completely as we know they present a hazard; other areas we get water without treatment.

Cheers

Edited by rcaffin on 01/09/2014 21:10:13 MST.

Buck Nelson
(Colter) - MLife

Locale: Alaska
re: Giardia on 01/09/2014 23:34:33 MST Print View

Tom, I'm afraid you don't recall correctly. It would have been farther north in the Sierra, I was southbound, and the spot I'm thinking of is up high.

As far as the definition of "pristine" I think we both have a pretty good idea of what that means. In GIARDIA: HUMAN HEALTH CRITERIA DOCUMENT, the EPA lists many studies and results from all water types, including pristine sources. I think professionals in the field of waterborne diseases would have a good understanding of "pristine."

Roger, you remind me of my early days on the internet when someone called me a liar because I said a drive to Alaska in March had been cold.

Don't assume I drew my conclusions from a single sentence or source. Here's another EPA quote Giardia cysts are ubiquitous in surface waters of all qualities. (GIARDIA: HUMAN HEALTH CRITERIA DOCUMENT) "Ubiquitous" is a much stronger word than "commonly."

It seems to me like the middle ground is where the truth lies, many people don't get sick drinking untreated water, significant numbers do. Most water has insignificant pathogen levels, some does. Statements like Rockwell's One conclusion of this paper is that you can indeed contract giardiasis on visits to the Sierra Nevada, but it won’t be from the water. are simply unsupported by the facts. That's the kind of thing I'm debating against.

Roger Caffin
(rcaffin) - BPL Staff - MLife

Locale: Wollemi & Kosciusko NPs, Europe
Re: re: Giardia on 01/10/2014 15:18:21 MST Print View

Hi Buck

I am still crying foul.

> Giardia cysts are ubiquitous in surface waters of all qualities.
But what does ubiquitous mean? It means 'found everywhere', but does not make any statement about quantity.

If every creek and pond has 0.01 cysts per litre, you could legitimately say the cysts are ubiquitous. But you could not say they are 'commonly' found in the creeks or ponds. In fact, it might be more accurate to say they are rarely found, or insignificant.

Cheers

Ben H.
(bzhayes) - F

Locale: So. California
Re: Giardia: Let's Talk SCIENCE on 01/10/2014 16:17:51 MST Print View

Buck, I haven't read through all of the responses (so sorry if you have already covered this). You requested feedback on your conclusions. In you article you state:

"The CDC SPECIFICALLY cited a Welch paper and said Although the advice to universally filter and disinfect backcountry drinking water to prevent disease has been debated (62), the health consequences of ignoring that standard water treatment advice have been documented in WBDOSS [Waterborne Disease and Outbreaks Associated with Drinking Water and Water] In other words, there is documentation, with data, by the Centers for Disease Control and Prevention, that Dr. Welch is wrong."

I consider that pretty serious misrepresentation of what the CDC is saying. They are most definitely not saying that Welch is wrong. They are saying his conclusions are being debated. Additionally, they are saying that IF you get giardia the health consequences are well documented. That is not drawing a conclusion about the effectivity of treating backcountry water.

Buck Nelson
(Colter) - MLife

Locale: Alaska
Re: Re: re: Giardia on 01/10/2014 18:28:54 MST Print View

Roger, I think "common" is a better synonym for "ubiquitous" than "rarely," but perhaps I'm just being stubborn and argumentative, know what I mean?

Ben, I disagree. the health consequences of ignoring that standard water treatment advice have been documented In that particular statement the CDC is saying they have documentation of the disease consequences of not always treating backcountry water. As a matter of fact, in that statement they don't even mention giardia specifically. They are saying that Welch has debated the issue, not that they are undecided, which is why they cited his article with the "(62)."

Katy Anderson
(KatyAnderson) - F
full sentence on 01/10/2014 21:10:46 MST Print View

This back and forth made me curious enough to go to the CDC article to see what you guys were talking about.

Here is a link to the document: http://www.cdc.gov/mmwr/preview/mmwrhtml/ss5709a4.htm

The quote is from a paragraph titled "Waterborne Disease and Outbreaks Associated with Water Not Intended for Drinking and Water of Unknown Intent" a couple of pages into the text.

The full sentence reads:

"Although the advice to universally filter and disinfect backcountry drinking water to prevent disease has been debated (62), the health consequences of ignoring that standard water treatment advice have been documented in WBDOSS, although they have not been well-defined through research studies."

That last part of the sentence, that Buck left out, changes the meaning considerably.

Greg Mihalik
(greg23) - M

Locale: Colorado
Re: full sentence on 01/10/2014 21:50:04 MST Print View

Katy -
"That last part of the sentence, that Buck left out, changes the meaning considerably."

The full paragraph -
"Backcountry travel (i.e., travel in wilderness environments) in the United States is an increasingly popular activity. In 2004, approximately 12% of Americans aged >16 years (approximately 26 million persons) went backpacking for one or more nights in backcountry areas during the previous 12 months (55). Limited information is available concerning the risk factors for illness in the backcountry and about the health outcomes of visitors who use parks in backcountry areas. Several studies indicate that as many as 3.8%--56% of long-distance hikers and backpackers experience gastrointestinal illness during their time in the backcountry (56--61). Given the increasing popularity of backcountry use, this burden of illness could have significant medical and economic implications. Although the advice to universally filter and disinfect backcountry drinking water to prevent disease has been debated (62), the health consequences of ignoring that standard water treatment advice have been documented in WBDOSS, although they have not been well-defined through research studies. "

What "meaning" changed, and how?

Edited by greg23 on 01/10/2014 22:44:17 MST.

Bill Law
(williamlaw) - M

Locale: SF Bay Area
Re: Re: Nelson's errors in a nutshell on 01/10/2014 22:57:31 MST Print View

A few minutes of Googling is not enough.

A *lifetime* isn't enough :-).

In 2004 they switched from chlorine to chloramine

Sorry; my mistake. I didn't see mention of that little detail anywhere; I now gather that the controversy was due to the fact that chloramine treatment seems to have more side-effects than chlorine.

your point about treatment effectiveness is invalid

Perhaps. While *optimal* chloramine treatment apparently *can* be effective, it isn't obvious that a given treatment with it is. Chloramines are relatively weak disinfectants for virus and protozoa inactivation, per the EPA, for example.

99.9% plus of those cysts would be dead

That isn't obvious to me. First, I still find it incongruous that the cited figures would be for input water. The EPA says in at least one place that it doesn't require measurement of a water system's inflow. And good luck figuring out whether the cited figures are for dead versus viable cysts (it isn't obvious to me how one can even tell one from the other). Regardless, it seems the numbers are pretty useless, regardless, *except* to compare to like numbers (which is what Rockwell did). Maybe the other numbers he cited included dead cysts, also?

a real-world water source which has likely never been tested in history and if it has, likely decades ago

Yet a few lines later you mention a scientist who has done precisely that testing (although I can't find any of his published numbers for Giardia). Rockwell provides citations which seem to contradict your statement. You do a good job of hedging your statement, though; is "likely" 50.1%? is "decades ago" 11 years ago, 16 years ago, or 20 years ago? Does it matter? You could cite Rockwell's paper on that point, but be careful, as we know that paper has at least 4 errors.

Read more here: http://www.modbee.com/2010/05/08/1158938/fouled-waters-sierra-lakes-streams.html#storylink=cpy

I did, including bacterial contamination was easily high enough to sicken hikers with Giardia. I wonder if it could give me the flu, also.

It goes on to say: at high elevations in Yosemite, Sequoia and Kings Canyon national parks, Derlet found a striking difference: Most lakes and streams were clear as champagne and pollution-free.

All in all, the news article you cite (not a technical paper, let alone a peer-reviewed one) is perhaps irrelevant to a discusson of Giaria.

The bottom line: I think to claim Rockwell is in error, one should have to point out the errors in his numbers, or, provide different numbers.

I think I've made this point before: despite your 4 nitpicky complaints with his paper, Dr. Rockwell could certainly have reached the right conclusion anyway. Until I read something that reaches an opposite conclusion and is equally comprehensive and accompanied by as much supporting material, I'm going to continue to drink freely and confidently.

Buck Nelson
(Colter) - MLife

Locale: Alaska
Definitions on 01/11/2014 00:15:35 MST Print View

Katy: "although they have not been well-defined through research studies." What do you think that means? The source link is cited on my blog so people could read the whole thing in context if they liked. I do think the whole statement paragraph clearly supports my statement. The CDC is specifically addressing Welch's claims that there is little or no evidence that drinking untreated backcountry water involves significant risk.

Bill: SF water being run through a modern water treatment plant is not a little detail.

I have talked to the water treatment folks for SF at least three times. The last person cited the water report in saying that the cyst count does not factor viability. So the count, whether at the input or the output, (I have now also heard both,) will end up with a full 3-log plus reduction after treatment.

The fact remains that the actual surface water in the backcountry a hiker is going to drink almost certainly hasn't been tested recently enough (and probably not at all) to be a dependable indicator of pathogen levels.

The bottom line: I think to claim Rockwell is in error, one should have to point out the errors in his numbers, or, provide different numbers. If you don't see any significance in Rockwell's viable giardia numbers for city waters being orders of magnitude lower than he claimed, I beg to differ. And you don't think it's significant that the minimum dose that can sicken someone is not 10 cysts, as Rockwell claims, but one?

"4 nitpicky complaints?" Hardly. They are probably the four most-quoted points of his whole paper, and are the very heart of his arguments.

Edited by Colter on 01/11/2014 10:25:36 MST.

Roger Caffin
(rcaffin) - BPL Staff - MLife

Locale: Wollemi & Kosciusko NPs, Europe
Re: Re: full sentence on 01/11/2014 14:51:17 MST Print View

> Several studies indicate that as many as 3.8%--56% of long-distance hikers and backpackers
I will stick my neck out and suggest that any survey which produces a result like '3.8% to 56%' is meaningless. You might just as well write 0% to 100% imho.

> bacterial contamination was easily high enough to sicken hikers with Giardia.
Ahhhh... Giardia is protozoa, not bacteria. Any article which confuses the two should probably be used as TP.

There's an awful lot of blathering about this subject, mostly totally incompetant. Compare with the risks of being killed while driving to the trailhead.

Cheers

Edited by rcaffin on 01/11/2014 14:55:21 MST.

Bob Gross
(--B.G.--) - F

Locale: Silicon Valley
Re: Re: Re: full sentence on 01/11/2014 15:40:58 MST Print View

"I will stick my neck out and suggest that any survey which produces a result like '3.8% to 56%' is meaningless."

Roger, if you go re-read the posting, that is not what was stated. Surveys and studies may be two different things. Also, one is not the same as several. Why do you like to twist the wording around?

For example, one broad study might yield a result as bad as 56%. One narrow study might yield a result of 3.8%. Without knowing the total samples of each study, we don't know how much faith to put in one or the other. That's how they come up with phrases like 3.8% to 56%. That means that there is wide divergence into how bad the problem really is.

--B.G.--

Buck Nelson
(Colter) - MLife

Locale: Alaska
Re: Re: re: Giardia on 01/11/2014 16:12:37 MST Print View

Roger said: > Several studies indicate that as many as 3.8%--56% of long-distance hikers and backpackers
I will stick my neck out and suggest that any survey which produces a result like '3.8% to 56%' is meaningless. You might just as well write 0% to 100% imho.


Firstly, they used the word studies (plural) and not survey (singular.) They are referring to not one survey (which might be informal and unscientific,) but multiple scientific studies. [I see Bob beat me to this point.]

Secondly, that quote is from the Centers for Disease Control. In general, people would be well-served if they listened to professional epidemiologists and not the humble opinion of internet people.

Thirdly the CDCs stated range for gastro trouble among hikers is far from meaningless for seemingly obvious reasons. Note their range is "3.8% to 56%" From Wikipedia: The National Outdoor Leadership School (NOLS), which emphasizes strict hand-washing techniques, water disinfection and washing of common cooking utensils in their programs, reports that gastrointestinal illnesses occurred at a rate of only 0.26 per 1000 program days. See the difference?

Roger said: > bacterial contamination was easily high enough to sicken hikers with Giardia.
Ahhhh... Giardia is protozoa, not bacteria.


That of course is a quote from a newspaper article summarizing Derlet's recent research. Just about any newspaper article I read about a topic upon which I am familiar makes some factual errors. Doesn't change what the study actually says though.

From Reducing the impact of summer cattle grazing on water quality in the Sierra Nevada Mountains of California In watersheds where cattle have grazed, 96% of surface water samples contained significant indicator levels of E. coli of 100 CFU/100 ml or more, placing these waters at high risk for harboring the large variety of harmful microorganisms (Derlet et al. 2008). Reducing the impact of summer cattle grazing on water quality in the Sierra Nevada Mountains of California All you have to do is know for sure that cattle haven't recently grazed anywhere in the entire drainage. Not so easy if there's no sign of cattle where you are. I think that's exactly what got me last time.

Roger said: Compare with the risks of being killed while driving to the trailhead. OK, I think drinking untreated water is far less dangerous. Beyond a reasonable doubt however, drinking untreated water has cost me a lot of time and money and discomfort. I do my own risk assessment.

Roger said: There's an awful lot of blathering about this subject, mostly totally incompetant. Pretty poor representation of moderation on the part of someone on the BPL Staff.

Here are a couple of people who are willing to consider other points of view, think carefully, and exchange ideas politely; check out the posts on this thread by William Segraves and KatyAnderson.

Bob Gross
(--B.G.--) - F

Locale: Silicon Valley
Sadism, Necrophilia, and Bestiality on 01/11/2014 17:43:19 MST Print View

" [I see Bob beat me to this point.] "

We're beating a dead horse.

--B.G.--

Roger Caffin
(rcaffin) - BPL Staff - MLife

Locale: Wollemi & Kosciusko NPs, Europe
Re: Re: Re: Re: full sentence on 01/12/2014 00:05:42 MST Print View

Hi Bob

> For example, one broad study might yield a result as bad as 56%. One narrow study
> might yield a result of 3.8%. Without knowing the total samples of each study, we
> don't know how much faith to put in one or the other.
Happens I actually agree with you.

The survey in this case was that by the CDC which produced these figures from a number of studies. But with such a wide range of results one has to conclude that none of them are reliable. Alternately, depending on one's point of view (or vested interest), with those results one can claim any value one wants. You want a real low value? Try this paper. You want a real high value? Try that paper.

In short, the results are meaningless, except that they show that one can get Giardiasis from the mountains.

Now, am I implying that either Bob or Buck is incompetent? Nope. Never said that.

Am I suggesting that the newspaper report was incompetent? Too right. The problem with quoting such a 'report' is that if left unchallenged it becomes part of the folklore. So I pointed out that it was illogical.

Cheers

Roger Caffin
(rcaffin) - BPL Staff - MLife

Locale: Wollemi & Kosciusko NPs, Europe
Re: Re: Re: re: Giardia on 01/12/2014 00:23:35 MST Print View

Hi Buck

First, see above reply to Bob.

> Roger said: There's an awful lot of blathering about this subject, mostly totally
> incompetant. Pretty poor representation of moderation on the part of someone on
> the BPL Staff.
First of all, not every posting of mine is 'moderation' (either as 'mild' or as 'moderator'). I am entitled to my opinion, just the same as everyone else. And sometimes I am a bit too concise.

Second, I stand by my comment about blathering, but perhaps I need to clarify that I was referring to things like the newspaper article. Any reporter who confuses bacteria and protozoa is clearly way out of his depth, and is blathering. I was not referring to either you or Bob. Sorry if you thought otherwise.

I note the interesting figure you quote from NOLS of '0.26 per 1000 program days'. Seems to me that is a lot less than 3.8%, however you define the conditions. That said, I think it brings a lot of the debate back into perspective, and that data is probably more reliable then many so-called research papers with relatively tiny study populations or uncontrolled self-reporting.

However, bear in mind that the NOLS data does not mean the 0.26/1000days figure must come from water supplies. It could equally come from a few cases where kids did not wash properly. That NOLS get such good results by being aggressive with the demands on hand washng does imply that without that aggression the figures would be far worse - which says something about the NOLS participants. Interesting data, but no controls for comparison.

> In watersheds where cattle have grazed, 96% of surface water samples contained
> significant indicator levels of E. coli of 100 CFU/100 ml or more,
Now that is a useful bit of information for everyone, but hardly unexpected. Me, I would round the figure up to 100% just to be safe! Thank you for that.

Cheers

Jennifer Mitol
(Jenmitol) - M

Locale: In my dreams....
Re: Sadism, Necrophilia, and Bestiality on 01/12/2014 07:50:38 MST Print View

Well Buck, I appreciate your beating this dead horse. And despite my temptations on numerous occasions to drink that "pristine" water, I have taken your advice and treat no matter what.

Besides, after watching all those trains of pack animals trudge through those "pristine" streams and defecate right next to the lakes along the JMT...I would never drink from that water without treatment.

And I do wish people would stop substituting personal anecdotal experience for scientific studies. Just because YOU haven't gotten giardia from 20 years of drinking untreated water doesn't mean it's not in the water.

We used to think bleeding people helped them overcome illness because WE SAW IT! They had a fever, we put leeches on them, they got better...Of course!!!!!

William Segraves
(sbill9000) - F - M
Re: Re: Re: Re: re: Giardia on 01/12/2014 09:27:54 MST Print View

"I note the interesting figure you quote from NOLS of '0.26 per 1000 program days'. Seems to me that is a lot less than 3.8%, however you define the conditions. That said, I think it brings a lot of the debate back into perspective, and that data is probably more reliable then many so-called research papers with relatively tiny study populations or uncontrolled self-reporting."

NOLs purifies their water. It's the comparable frequencies for those who *don't* purify the water that we'd most like to know about, right?

Bill S.

Katy Anderson
(KatyAnderson) - F
not well-defined on 01/12/2014 12:50:06 MST Print View

Greg says:
What "meaning" changed, and how?

Buck says:
What do you think that means?

Sorry, I must have been unclear in my original post. I will try again.

The part of the sentence that Buck quotes in his blog post is:
"Although the advice to universally filter and disinfect backcountry drinking water to prevent disease has been debated, the health consequences of ignoring that standard water treatment advice have been documented"

Reading this I infer that drinking untreated water has bad health consequences and the CDC has the data to back that statement up.

The part of the sentence that Buck left out is:
although they have not been well-defined through research studies."

This for me puts the first part of the sentence in a totally different light. Why?
Because as I read it the CDC is saying that the health consequences of drinking untreated water was not well-defined through research studies.

Which puts us all back at square one.
Question: What happens if you drink untreated water?
Answer: Not well-defined through research studies.

jerry adams
(retiredjerry) - MLife

Locale: Oregon and Washington
Re: not well-defined on 01/12/2014 13:37:55 MST Print View

Other half of the equation is what's the cost of treating

$20 and 2 ounces for Squeeze Mini. Minor hassle.

or other treatment methods