Colorado Trail water treatment (or not)

[Shawn Bearden]

I’ll be hiking the full Colorado Trail as soon as Waterton opens this summer (possibly before, by entering 6 miles up). So, hopefully all water sources should be flowing well and it’ll be early in the season. Given the trade-offs of effectiveness of AM (or similar) for viruses and bacteria (I won’t carry for 4 hrs to be effective on Giardia), and a filter (like Sawyer squeeze, which I have) for bacteria, Giardia and Crypto, which is the better choice? Put another way, along the CT, is there more likely to be problematic virus or bacteria/Giardia/Crypto? Or…is it highly unlikely that I would encounter levels high enough of any type at any source at that time?

[Ron D]

Hi Shawn – I got Giardia on the Colorado Trail this last summer and had to bail.  Strongly recommend taking the filter.

Ron

[Shawn Bearden]

Thanks! Bummer! What were you doing for treatment? Any idea where/segment you got it? Sure it was water and not hygiene (yours or others, no offense)?

[ed hyatt]

I used a Sawyer for my CT thru in 2013 – worked out well. Most I saw used them although did meet one chap who was not filtering.

[Jennifer Mitol]

there are so many cows on that trail – there is no way in the world I would even think of not filtering!  they were high, they were low, they were even right on the trail.  And yes, right by water sources.  I can honestly say I have never, ever seen so much cow s**t in my life.

[Buck Nelson]

Bacteria/Giardia/Crypto is much more likely to be a problem than viruses.

The paper Giardiasis in Colorado: an epidemiologic study. said:

A one-year retrospective laboratory survey in Colorado revealed that 691 (3%) of 22,743 stool examinations for ova and parasites were positive for Giardia lamblia, a higher percentage than that reported from surveys outside of Colorado. The majority of infected residents who were surveyed had experienced an episode of chronic watery diarrhea (median duration 3.8 weeks) with bloating, flatulence, and weight loss (averaging 5.1 kg), and had responded to a course of metronidazole or quinacrine. A statewide telephone survey of 256 cases and matched controls identified: 1) and increased incidence of giardiasis in persons between the ages of 16 and 45, p less than .001, with males and females equally affected; and 2) a higher proportion of cases than controls who visited Colorado mountains (69% vs. 47%), camped out overnight (38% vs. 18%), and drank untreated mountain water (50% vs. 17%), p less than .001. Also identified was a correlation between the seasonal distribution of cases and degree of fecal contamination of mountain streams. These results indicated that G. lamblia is endemic in Colorado and that drinking untreated mountain water is an important cause of endemic infection.

As far as wait time, Crypto is by far the toughest to kill with Aquamira. McNett says Under worse case scenarios (really cold and turbid water), it could take up to 4 hours to effectively remove Cryptosporidium.

Generally I rely on Aquamira. For the CT and cold water I might go with the Sawyer.

[Valerie E]

I used a Steripen for my CT thruhike last summer — but in areas with known stock traffic, I double-treated by using the Steripen, followed by Aqua Mira drops (in 2 tiny squeeze bottles).  This also took care of any icky manure-y odour/taste.  I never got sick.

One of my friends was a couple of weeks ahead of me.  She used old-school filters (Katahdyn, then MSR), and got giardia shortly after finishing her thruhike.  BTW, she was in a group of four women, and none of the other three got sick, so I guess she just drank the wrong sip of the water everyone else was drinking…

+1 to Jenn’s observation of mucho cow poop.  I found it particularly distasteful to smell/see it while I was getting water in a stream (and it was everywhere, so you really couldn’t avoid it in some areas!).

[John S.]

L’eau de manure.

[Shawn Bearden]

I will treat for sure. Probably filter given all I’m hearing about is Giardia. If your friend got sick and was drinking the same water as three others who didn’t, sounds like a good chance she didn’t get it from the water. She may have but quite possibly not. I’ll use my Sawyer squeeze.

[Shawn Bearden]

I’m assuming, too, that these cases of Giardia you folks are relating are confirmed Giardia and not only ‘symptoms consistent with Giardia’.

[Buck Nelson]

In the paper I cited it was 691 cases of lab-confirmed giardiasis cases with 256 of those being part of the survey.  People drinking untreated mountain water got giardiasis at 3 times the rate of controls. There is no question some people are getting giardiasis from untreated backcountry water, specifically in Colorado.

[ed hyatt]

The cows must have been restless for you guys then – I only recall one section of a few hours that was a pancake fest….

[Ron D]

Hi Shawn – I usually use a Steripen but accidentally left in the car for the first few days and had to use my backup Micropur.  I didn’t wait the full 4 hours.

Ron

[Keith Roush]

Yes to above, cows down low, with mountain goats, sheep and marmots up high.  Marmots and beaver alone are enough to cause giardia, before you count the 100’s of sheep and goats.

[Dean F.]

Giardia is one of Buck’s hot-button topics.  And he’s right, but it is important to remember that 3x (a really small number) is still (a really small number).

Nonetheless, heck yes, I’d go with a filter.  In fact I will almost always go with a filter over chemicals if I must choose one.  Why?  Because a filter is best for rapid clearance of the critters that are most likely to get me seriously ill, including bacteria and, yes, Giardia and other parasites.

Here’s what I’m thinking:

As you mentioned, most viruses you’ll have to worry about in the backcountry come from human contamination of water sources i.e. some moron crapping too close to the water, because worrisome waterborn viral zoonoses are not very common in North America.

So my first point- which isn’t helpful in this case- is that I personally am philosophically predisposed to tend to try to get remote and far away from impacted sites.  Thus, I should have low risk for human viruses.

But more importantly, my second point- what viruses are we talking about?  Random annoying viral enteritides might be intensely non-fun, but they often have long incubation periods that let you get home before you’re symptomatic and they are self-limiting and non-life-threatening in general.  So among common waterborn viral illnesses what scares me is Hepatitis A, against which I am immunized.  Yes, there are other scary ones but lets be realistic about what you will encounter in North America.  HepB and HepC are the truly scary ones, and there is no vaccine for it C, but they’re not waterborn.  HepD is a sort of hitchhiker on HepB.  HepE is waterborn but rare in developed countries.  Polio is terrifying but essentially every westerner is immunized against it unless their parents were anti-vaccine freaks (who should be prosecuted for child endangerment).  A viral meningitis would be Very Bad but that would be an off-the-wall thing and you’d be at much higher risk in a college dorm than in the Colorado backcountry, so yeah I guess about the only really scary thing left to worry about is a random freak Coxsackievirus giving you meningitis or some other odd affliction.

So in general I feel pretty good with a filter.

That said, if viruses concern you it is easy enough to carry a dropper bottle of your chemical of choice and add a couple of drops to every filtered liter to be sure you hit the viruses, too.  Once the water has been filtered and thus has no sinkies or floaties the viruses are very exposed and the chemical will kill them quite quickly.  In fact household bleach should work just fine for this application.

[Buck Nelson]

And he’s right, but it is important to remember that 3x (a really small number) is still (a really small number).

According to the CDC: “Annually, an estimated 1.2 million [giardiasis] cases occur in the United States” and among those are greatest risk are …”Backpackers or campers who drink untreated water from lakes or rivers”

[Dean F.]

Buck, I just said it was a small number, which it is.

It is interesting that the very first source you link to does not report ‘1.2 million cases annually’.  In fact it says about 16,000 cases are reported annually, with only six states not reporting, and this includes non-confirmed cases.  So let’s round that up to a risk of 0.0006% annually for cases severe enough that they don’t just go undiagnosed as yet another random enteritis.  Does that not strike you as a “small number”?

So I think I’ll stand by that statement.  And frankly a large preponderance of cases are in children, so adult risk is even lower.

The 1.2 million per annum claim is from different paper in the bibliography of the one you linked, so you really should have cited that instead, but I quibble.  Being by nature an untrusting sort, I looked it up for you.  That paper in fact claims about 20,000 reported cases annually, and this is older data from 2002-2007 (rates have fallen considerably since then).  They then try to estimate under-reporting (they claim a factor of 1.3) and under-diagnosis (they claim a factor of 46.3).  So, how did they get those estimates?  The 1.3 under-reporting is a blanket estimate they get by comparing rates in the national passive reporting system with rates in local active reporting systems for all parasites.  Probably reasonable, though Giardia-specific data would have been better.  The 46.3 for under-diagnosis is much more complex- it’s covered on page 19 of this appendix– involving nine other derived data sets, each of which involves it own error.  All of the numbers they used are cited from other studies at varying degrees of separation and of varying ages, too, so as you might imagine there is a hell of a lot of potential cumulative error there.  But we really don’t have anything better, so that’s what we have.

That’s how they get an estimate of 1.2 million annually.  Kind of shaky, but not a bad technique I guess.  If you use more recent reporting rates (2011 and 2012) the number is only 960,000 cases annually, though.

So consider this- cases that aren’t diagnosed weren’t severe enough that the doc thought it was worth testing or even empirically treating for Giardia, either of which would trigger reporting, which sort of makes it pointless to worry about that.  Further, again from that study, estimated hospitalizations for Giardia are 8.8 annually.  Yes, almost nine.  Not nine thousand, not nine hundred.  Nine.  Statista.com claims only about 12% of the US population (~38 million) goes on a hike in any given 12-month period.  So some quick and admittedly very specious math with your cited 3x risks produces an estimate of a bit less than 3 hikers who get hospitalized annually, and even then one of those three is not hiking-related.  This all contributes to my statement that 3x (a really small number) is still (a really small number), which again I stand by.

But even if you do want to use that 1.2 million number that’s still only 0.38% annually- still a rather small number.  Statistically, and again using some very specious math, a person would have to live almost 300 years (on average) to contract once case of Giardia.  If we accept your 3x risk (which I haven’t yet, but for the sake of argument) then assuming that you hike every year of your life for a century you will statistically get one case of Giardia, which will will likely (1:60) be mild and will almost certainly (1:400,000) not require hospitalization.  If you have a 50-year hiking career, which seems more reasonable, then you have about a 65% chance of getting Giardia at some point in your life, if you live for a century.  However, that study also estimates an average of one death from Giardia in the US every decade or so (0.1 per annum) which is why I don’t poo-poo the risk and recommended a filter.  This is about a 0.00000003% annual risk of dying of Giardia in the US.

And the second link you cite is a just a bibliography with no data, so it was pointless.  If you’re going to cite a paper, cite the paper.

 

(See what I mean about hot-button topics?)

:)

EDIT–  That Unhelpful button isn’t really supposed to be an “I disagree with you” button, Brother.

[Buck Nelson]

Dean, I will trust the CDC’s estimates over your self-described “specious” math.

And the second link you cite is a just a bibliography with no data, so it was pointless.  If you’re going to cite a paper, cite the paper.
See the “General Epidemiology” tab on that page? Click on it.

The CDC knows the reported cases are the tip of the iceberg. The physician who treated me in Mammoth said he treats many cases and doesn’t report them.  To quote a doctor from the same hospital, as reported in the LA Times: Several backpackers appear weekly at Centinela Mammoth Hospital in Mammoth Lakes sick enough with giardiasis to need urgent care, said Dr. Jack Bertman, an emergency physician, No giardiasis cases were officially reported to the CDC my year in that county and trust me, I was really sick.

This paper says there are about 5,000 giardiasis hospitalizations annually and that about 98% of cases are waterborne.

Statistically, and again using some very specious math, a person would have to live almost 300 years (on average) to contract once case of Giardia

That’s not what An outbreak of giardiasis in a group of campers found: Twenty-five other campers had stools examined before and after a subsequent hiking trip in another area of Utah; none had Giardia cysts before, but 6 (24%) had them after return. In the Zell study at least 5.7% of the backpackers studied became infected on a single trip (verified by lab tests.) Those are the best studies of their kind.

[Dean F.]

Ah, I see your table.  Interesting that hikers who drink untreated water are just one group among seven who are described as at increased risk.  Well, no one here is proposing not to treat water, eh?  Also interesting that you’re harping on under-reporting when I have just quantized it.  :)  It’s a factor of 46.3.  The hospitalization rate of 9 per annum takes this into account.

Go ahead and believe the CDC.  I didn’t say that you shouldn’t.  But put their numbers in perspective- as I have shown they are a small fraction of total US population- and bear in mind that many studies are old or poorly designed, they often produce conflicting results, and that many lay people make spurious conclusions from the data.  Because when you trot out impressive-sounding sensationalist numbers like “one million Giardia infections annually!” it’s important to remember that only 16000 are ever verified annually.  So only 16000 were severe enough to bother testing for stool ova.  And, frankly, now that I have investigated where that estimate came from it turns out that many of them probably aren’t even symptomatic.  They just pass cysts for a while then their body clears the infection and they never even knew they had it.

That’s the actual lesson from the Zell study that you link- that very few Giardia exposures even get symptomatic before they clear.  Giardiasis is a disease defined by symptoms, so since none of these people had symptoms none of these people actually had giardiasis.  They passed some cysts, yes, but they weren’t sick because they did not get the minimum required 10 cyst innoculum, so their bodies eventually killed off the infestation and they just passed cysts for a few days.  This is what most of your million cases of Giardia infection annually are like.  Zell even calls it “cyst acquisition” rather than “giardiasis.”  He also cites single-digit per 100 gallons cyst loads in the three water sources he tested, and all of the hikers who actually had intestinal distress in the study were negative for Giardia cysts.  Thus his conclusion is in fact precisely the opposite of what you propose: he concludes that something other than giardiasis explains the vast majority of intestinal distress among hikers.  To quote him, this study “dispel[s] the notion that this parasite is ubiquitous and causes widespread illness.”  He describes the acquisition rate in this high-use area as low, and points out that no symptomatic illness could be attributed to it.

So you learned the wrong lesson from that study, Brother.

Interestingly, the Mead paper from 1999 cites “n/a” as the hospitalization rate for Giardia infections.  Yet they estimate 500 for food born hospitalizations later, not the 5000 which you quoted- that’s the total, not the ones that are food born.  And that’s what we’re talking about isn’t it?  We’re not talking about men who have sex with men?  And it turns out that they got those numbers by making very specious extrapolations from two studies in 1989 and 1992 from small regions of Wisconsin and Vermont.  (Again, you really should cite the original papers.)  And, again, old data (rates are lower now), with huge error bars, and not very widely applicable.  And it seems that a preponderance of other papers supports a much lower number.  Also of note is that their estimate of non-reporting are lower than in that other paper- a factor of 20 instead of 46.3.  So who is right?  500?  Or 9?  You linked both papers, but you like 500 better so that’s the number you picked (well, actually you picked 5000) when you needed to cite a number.  But 9 comes from the more rigorous study based upon more comprehensive and more recent data.

The Barbour paper describing one infection cluster in Utah in the 1970s is not very helpful because that’s exactly what it is- a case report of a single infection cluster 40 years ago.  Zell’s is rather better.

A newspaper article from 1988 with one doc’s single-sentence anecdote is also not very convincing.  It’s old, and see below about over-diagnosing.

A preponderance of data supports what I have contended- that disease from Giardia is a small number.  In fact, there is a problem with doctors in the US empirically over-diagnosing for parasitic diarrhea.  “Oh, you were hiking and now you have diarrhea?  It must be Giardia.  Here’s some Flagyl.”  When in fact it is almost certainly something other than Giardia, as Zell maintains.  Giardia is indeed the most common parasitic infection in the US, absolutely, but that’s still a small number and certainly not some sort of deadly plague.  It’s worth worrying about, but most hiker intestinal distress is from something else.  I’m not sure why it offends you any time someone says that Giardia isn’t quite the massive problem that we had been led to believe in the past (you do seem to favor old date from the 1980s, which was the high point of this panic).  I have said that I would advise taking a filter for bacteria and parasites rather than worrying about viruses, just as you did.  Because when Giardia is bad it is truly memorable.

[Buck Nelson]

The reason I quoted those two papers is they are the only papers in existence that tested hikers before AND after their hikes, proving hikers were getting giardia while hiking.

So only 16000 were severe enough to bother testing for stool ova…  Absolutely false. Last time I had a bad case I was not lab tested. If you think that both the physician and I were wrong on that diagnosis I vehemently disagree. I’ve got experience with that particular bug, and that doctor has a whole lot more.

Giardiasis is a disease defined by symptoms, so since none of these people had symptoms none of these people actually had giardiasis…Then why does Google Scholar have over 300 references to “asymptomatic giardiasis?”

One of the Zell hikers was empirically treated for giardiasis, the only one of the sick hikers who hadn’t been treating his water. Tests often miss giardiasis.

They passed some cysts, yes, but they weren’t sick because they did not get the minimum required 10 cyst innoculum… That’s a common fallacy that even some experts repeat. The definitive paper estimated a 2% risk of infection with a single cyst.

 To quote him, this study “dispel[s] the notion that this parasite is ubiquitous…  Apparently it hasn’t, As of 2016 giardia is commonly considered ubiquitous.

 “Oh, you were hiking and now you have diarrhea?  It must be Giardia.  Here’s some Flagyl.”  When in fact it is almost certainly something other than Giardia.
That’s not a study. That’s not even an anecdote.

…certainly not some sort of deadly plague… No one suggested it was.

I wrote this for Appalachian Trials.

 

 

[Billy Ray]

Papers schmapers… who cares…
It silly to not treat your water.
There is no way to tell by looking what is in or not in the water.
(regardless of how many papers you’ve read of studies done)
Treating it is simple, easy, cheap, practical, and doesn’t require much weight.
Cheap insurance against being sick, me thinks.

billy

[Dean F.]

Buck, you keep quoting papers that you try to present as “definitive” or “the best we have” that do not prove what you think they prove. You are not reading them critically. You’re pulling a number from them without digging into what it is really measuring.

For instance, in your latest ‘definitive’ paper a positive infection was defined as producing cysts in the stool. It was not defined as having symptoms. Yes, if you take a small inoculum you will produce cysts in the stool, but your body will clear them before you become symptomatic. (Despite that, from a public health perspective I do agree with the paper’s conclusion that we should probably aim for lower concentrations in our treated drinking water. A person passing cysts is still passing cysts, even if asymptomatic, and is thus a carrier spreading it about.)

They call it “asymptomatic giardiasis” because there is nothing else to call it, and that phrase does get the point across- it is understood. To quote Mayo clinic, giardiasis is “an intestinal infection marked by abdominal cramps, bloating, nausea and bouts of watery diarrhea.” On the other hand and in the interests of full disclosure CDC does say “the spectrum varies from asymptomatic carriage to severe diarrhea and malabsorption” but that phrase isn’t directly linked to the word “giardiasis”, so it may be a more generalized statement about giardia infestations. So maybe we’re quibbling over semantics but my point is that if you are asymptomatic then you aren’t sick, almost by definition. Just as you can be exposed to TB and even test positive on your PPD yet not have tuberculosis!

If you weren’t lab tested during your last illness then you weren’t well diagnosed, no matter what your opinion is of your own or your doctor’s familiarity with the disease. Empiric over-treatment is a problem, and there was no reason not to test for it unless the patient can’t afford it or something. Just off the top of my head I can think of three or four more likely candidates, all bacterial. You’re just fortunate that the same agents treat most of them. And just like you, that one Zell hiker was empirically treated for giardiasis when statistically speaking he probably didn’t have it. But docs (and I’m guilty, too) do err on the side of not taking chances. Recall: of the 16% of Zell hikers who got sick none of them tested positive and of the 5% who tested positive none got sick. So you can pick any cherries you like, but that data stands.

Your claim that the testing has a lot of false negatives because cyst excretion is episodic was true… decades ago. And that’s why a proper test involved three samples, not just one. But this is no longer true with modern immunoassays. Zell used an especially sensitive immunoassay, which explains why the study caught so many asymptomatic infestations. This is why I can say that almost certainly the negative hiker who was treated for giardia was over-diagnosed. Some of the studies on the immunoassays quote an essentially 100% specificity and sensitivity. More believable ones quote around 98%, though, which is damned good, Brother.

Of course, if you’re someplace remote and they only have a microscope and can’t do an immunoassay then clearly you have to do the three stool samples.

“…is commonly considered” means nothing without a cite. It’s not even allowed on Wikipedia. :) I can tell you about all sorts of outdated stuff that gets propagated through the medical establishment, so I don’t find your use of that phrase very convincing, and your primary care doc isn’t exactly the specialty that goes to giardia conferences. Incidentally, I guess it’s worth pointing out that you have stumbled into a bit of a religious war in medicine, here: the old-school empiricists vs new-school evidence-based docs. I’m one of the newer-generation evidence-based doctors, Buck, so given the data I’ve seen I would call giardiasis serious, but not “ubiquitous”. “Ubiquitous” almost implies that it would be impossible not to catch it if you drank untreated water, which is clearly nonsense.

“It must be Giardia, here’s some Flagyl” absolutely is a study. Zell. You yourself just mentioned that a negatively tested hiker got treated, right? :) And you just mentioned a case where you were treated without a lab test. You’re making my argument for me! (At least an anecdotal one.) I’m also a member of the Wilderness Medical Society (WMS) and have been to their conferences, and this does get discussed as a problem, with Giardia prominent in the discussion. Over-prescription of antibiotic agents is such a problem in the US that it gets discussed on Oprah, for God’s sake. Really? You’re going to contest this? Buck, I live this.

If you didn’t suggest it is a deadly plague, well, then you are certainly at the least sensationalizing it. It is indeed your hot-button subject. But I’ll apologize for the innocent hyperbole, if you like. Giardia isn’t everywhere. It’s just our most common waterborn intestinal parasite.

your Appalachian Trails article is pretty good- it gets the point across, especially for laymen. But it is just a bit misleading, for the reasons I have shown above, even if I agree with your conclusions that we should all be treating our water.  I guess that rather than implying “It’s everywhere!” I would prefer to say “You could encounter it anywhere, and although usually in low concentrations God help you if you drink untreated water from a concentrated source.”
And I’m done arguing with you. Go do another of your epic hikes, Buck. I’m envious.

[Nick Gatel]

I think we all agree that almost all water in the back country should be treated, irregardless of what papers are published or how we study them. I have never gotten a waterborne disease and have been treating nearly all my water for over 50 years.

The important thing is to follow the treatment instructions!

I find it amusing that many people want to carry all sorts of communication devices for rescue, which most will never need, but they don’t want to properly treat their water. I’m not saying the devices are bad, but too many folks have their priorities backwards.

[Paul Magnanti]

..and don’t forget proper hygiene  and cleaning of yourself and eating gear. If you share food, pour it into another person’s hands and don’t let them grab from your food bag.

A few simple steps that will prevent GI type illnesses.

 

 

 

 

 

[Dean F.]

Yes, that’s more or less what I’m saying, Nick. Have I ever drank untreated water? Yes, guilty. But only meltwater directly from a glacier or snowfield. Yes there is still a risk, but it’s damned small. Otherwise I don’t see why one wouldn’t at least filter it, even if only a coarse filter for parasite cysts. Most water born parasite infections can be miserable and damned hard to eradicate once they are established. And even if they aren’t “ubiquitous” it can be nearly impossible to discern which sources are heavily impacted. So why take that chance?

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