Giardia: Let’s Talk SCIENCE

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)."

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.

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?

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.

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.

> 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

"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.–

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.

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.

" "

–B.G.–

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

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

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!!!!!

"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.

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.

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

William wrote:

> > interesting figure you quote from NOLS of '0.26 per 1000 program days'.
> NOLs purifies their water.

Hum – interesting. IF NOLS treats their water with something meeting EPA Standards, then where did the 0.26/1000 get their infection? I don't know.

Cheers

Katy –

"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."

So even though consequences have been documented, you will wait for "well-defined studies" before deciding to treat your water?

"IF NOLS treats their water with something meeting EPA Standards, then where did the 0.26/1000 get their infection?"

I've seen lots of beginner backpackers who start with a proper filter, but their use technique is lousy. I've seen beginners rinse out cookware with raw water, and then use it immediately.

–B.G.–

Roger –
"Hum – interesting. IF NOLS treats their water with something meeting EPA Standards, then where did the 0.26/1000 [program days] get their infection? I don't know."

Poor personal hygiene, spread through sharing food, or food prep, would be my guess.

Even though NOALS goes to great lengths stressing proper toilet activities, it would not surprise me if someone out of a group of 20, over the course of 30 days in the field, times 70 trips, didn't get it exactly right.

Edit 1: And IIR, one case study (not NOALS) traced GI problems to soapy cookware as a result of poor rinsing. So, not all GI episodes are microbe related.

Edit 2: I personally observed a NOAL dinner where "fresh/frozen" chicken was being prepped for inclusion into burritos. I didn't see a lot of hand washing or utensil segregation during that process, and Hoped that things were being well cooked. They did taste great!

Jennifer: Thanks for that. I think it's worthwhile and I actually think we've covered lots of new ground on this thread along with the standard debating points.

Bill said: 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?" That's true. There's not a good matched control group, but I think the results of their handling of water, hands and cookware vs the general public is meaningful.

"Medical risks of wilderness hiking" which may or many not have been mentioned on this thread, did a study on a large group of backpackers and found, like NOLS: Diarrhea is the most common illness limiting long-distance hikers. Hikers should purify water routinely, avoiding using untreated surface water. The risk of gastrointestinal illness can also be reduced by maintaining personal hygiene practices and cleaning cookware. http://www.ncbi.nlm.nih.gov/pubmed/12681456

Katy Anderson: I think they are clearly saying there is documentation of consequences for drinking untreated backcountry water. As you know we've discussed scientific papers containing some of that documentation on this thread. I THINK the CDC is saying there are gray areas (not well-defined by studies,)like the attack rates, risk factors, relative importance vs. hygiene, etc. Anyone know the definition of "well-defined" in this context?

Bob and Greg, Good points.

Whenever you look at review papers, or meta-analyses, they usually couch their findings with some sort of "need more research" statement. It is exceedingly rare to get a full on recommendation about anything medical at this point, as we are all well-aware of the limitations of the scientific literature.

HOWEVER…we do know a little. It may not be perfect, it may not be conclusive, but the literature that is out there certainly suggests that it is quite possible to be infected with giardia from untreated surface water in the backcountry. So until we have more studies that tell us otherwise, why in the world would you risk it? The cost-benefit ratio just doesn't seem to at all favor taking the risk.

Seatbelts? The likelihood of my getting into an accident is low, but I'm going to wear it anyway because the risk exists and I know a seatbelt will minimize the damage. Same with helmets.

I guess I just don't see why people are so rabidly anti-treating and feel the need to spread that word. If you want to take the non-treatment risk and drink horse poo, then go for it. But at least do it honestly…..

[major re-write to remove scientific assertions disguised as opinions]

Jennifer Mitol wrote: " So until we have more studies that tell us otherwise, why in the world would you risk it?"

In my case the answer is emotional: pure unadulterated joy. Rockwell's piece sent me back to my youth when I first fell in love with moving through nature, watching, learning, observing, sensing, and participating directly. Getting back into camping as an adult, suddenly there was a new bug and almost all of my college educated brainpower went into evaluating that. The joy I felt, unleashed by Rockwell, bending over to drink freely from a mossy springlet so presenting with the signs I'd learned how to identify clean water in the wild, is inexpressible. The joy of being a member and not engineer of nature.

But I feel I can say that from a position of informed, if not decimal-self-quantified, risk avoidance. I've read literature without reviewing as a peer. I merely believe/suspect that PPM and not single-cyst is material. Identifying bias and re-interpreting seems half the battle in learning from objective studies themselves.

"I guess I just don't see why people are so rabidly anti-treating and feel the need to spread that word. If you want to take the non-treatment risk and drink horse poo, then go for it. But at least do it honestly….."

First let me say, I treat all of the water I consume. I think the anti-treatment group is a backlash to fear mongering on the treat water side. People are seriously afraid of consuming water which is probably completely safe to drink. Thank can have real consequences. People could face serious dehydration and even death due to out of proportional fear of drinking untreated water.

I am all for getting the facts straight. I think people should evaluate the risks for themselves based on sound scientific research. I was really interested in this topic, but I think the OP got off topic right from the get go in trying to promote a specific conclusion. I think the science is up in the air as to whether it is necessary to treat certain backcountry water. We should be promoting what the science says, not spend all of our time telling people what to do.

There is a clear mountain stream in the Sierras that for many, many years we drank from without treating. No one had any problems (though I believe that I am "immune" to giardia). Then one of us got a filter and the water tasted better to me (no silt). So, I got a filter too, can't be left behind in the gear arms race! ;^) Now, I filter all the time, but I wouldn't hesitate to drink from that stream if I couldn't filter.

It comes down to it being so simple to filter that I do. The sawyer filters make this quick, easy and light. And one never knows when something can change. And, I don't have to evaluate each water source I come across. I don't have to pass up a questionable water source looking for a better one.

That said, way too big a deal is made about the dangers of drinking untreated water. The day hikers I rescued at Nevada Falls in Yosemite would have been way better off drink untreated water. Any problems would have occurred once they were safely home, instead of nearly passing out from heat exhaustion brought on by sever dehydration.

I really don't care what some study or peer reviewed paper has to say.
The truth is that my father and his father went on many backpacking trips where they didn't treat water. At the time nobody was treating water. They never got sick and nobody they knew ever got sick. I have met hikers who are twice or three times my age who have never treated and never gotten sick. Mountain water sources are the same as they were 50 years ago. This is why I don't treat much of my water.