View Full Version : Backpacker Giardia: The Science and the Evidence
After reading a purportedly scientific paper comparing the risk of giardiasis to the risk of shark attack, I stopped treating all my water and promptly got giardia for the first time in 20+ years.
Having done a lot of research now I've found many major flaws in said paper. I'd be delighted if those of you with a scientific mind would read through my findings (http://bucktrack.blogspot.com/2012/09/backpacker-giardia-debunking-skeptical_8.html)and tell me what needs to be changed to make it accurate, or why you think my conclusions are logical as written.
Thanks folks!
One thing that came to mind first was what the health department defines as an outbreak. Most health departments define an outbreak as two or more non-related persons becoming ill from a common source.
One thing that came to mind first was what the health department defines as an outbreak. Most health departments define an outbreak as two or more non-related persons becoming ill from a common source.
Thanks for the feedback! The definition I quoted is virtually identical to that used by the CDC, who say "outbreak" is synonymous with "epidemic."
Anything else?
One thing that came to mind first was what the health department defines as an outbreak. Most health departments define an outbreak as two or more non-related persons becoming ill from a common source.
Thanks for the feedback! The definition I quoted is virtually identical to that used by the CDC, who say "outbreak" is synonymous with "epidemic."
Anything else?
Sorry. I'm in agreement with you on the misuse of the word outbreak. If one hiker or a group gets sick it's not an outbreak. If two seperate people or groups gets sick and the only common thing is the water source then it can be an outbreak. Food borne illness works this way.
Do these scientific studies take dilution into account? The level of giardi in moving water must have a peak right after the fecal matter is deposited in a stream then becomes diluted to safe levels at some point. If this is true then a true outbreak is going to be difficult to define because the health department wouldn't have any evidence to test three or four days latter. Without any evidence the health inspectors I know are going to blame hygiene every time.
The link I followed to the studies you are looking at took me to the abstract, and not the full study-- I probably should have looked harder. I geve up.
After reading a purportedly scientific paper comparing the risk of giardiasis to the risk of shark attack, I stopped treating all my water and promptly got giardia for the first time in 20+ years.
And you were diagnosed with Giardia 2X before going with a filter, correct?
Not sure if your experience applies to the AT, but for where you draw water form and with your resistance to Giardia it seems like the value of a filter is clear cut.
For most peope on the AT, I think it is less so-- but I recognize you could be correct.
Question: What kind of filter have you been using? One of my (minor) concerns with filters would be that they could concentrate giardia in to a critical mass that would eventually leak out in full toxic concentrations.
Do these scientific studies take dilution into account? The level of giardi in moving water must have a peak right after the fecal matter is deposited in a stream then becomes diluted to safe levels at some point. If this is true then a true outbreak is going to be difficult to define because the health department wouldn't have any evidence to test three or four days latter. Without any evidence the health inspectors I know are going to blame hygiene every time.
That's the kind of critical thinking I like. That's an absolutely crucial point that Welch, Rockwell and other skeptics don't factor into their calculations. They repeatedly use averages, but you are exactly right. There are commonly peak points where the water will be loaded with literally millions, often tens of millions of cysts that will eventually be diluted to the point where the water becomes quite safe. Testing results depend on when and where the water is tested and the quality of the testing filters.
It will be extremely difficult to determine if it was dirty hands or bad water a week or two after the cysts were ingested. That's why I believe in restrospective case-control studies like this aforementioned one (http://www.journals.elsevierhealth.com/medline/record/ivp_00029262_105_330)that studied 256 giardiasis victims and found giardias cases were triple for those drinking untreated water.
The link I followed to the studies you are looking at took me to the abstract, and not the full study-- I probably should have looked harder. I geve up.
And you were diagnosed with Giardia 2X before going with a filter, correct?
Not sure if your experience applies to the AT, but for where you draw water form and with your resistance to Giardia it seems like the value of a filter is clear cut.
For most peope on the AT, I think it is less so-- but I recognize you could be correct.
Question: What kind of filter have you been using? One of my (minor) concerns with filters would be that they could concentrate giardia in to a critical mass that would eventually leak out in full toxic concentrations.
Hi Rick,
You're right, for most of those studies you have to pay to read them. It would be nice if they were in the public domain. There are a few studies linked on my blog that are fully downloadable, including the one I am specifically debunking.
I've pretty much always treated or filtered. The first time I got giardia I have no idea how I got it. The next time I was extremely thirsty fighting a forest fire and drank out of a spring. The next time I was drinking unfiltered Sierra water after having been convinced it was safe to do.
Perhaps this has been linked to many times but it is a large study of AT hikers (http://onlinelibrary.wiley.com/doi/10.2310/7060.2004.13621/abstract)and unsurprisingly it shows filters and good hygiene both make a difference in hiker health but unfortunately doesn't specifically address giardia.
Every person and every water source is different. I don't mind if people look at the facts and decide not to treat their water.
I've always thought about filters failing and releasing all the baddies at once. Never heard of it but it seems it could happen. I have used filters but currently use Aqua Mira drops.
Saying "I don't treat my water and I've never gotten sick." is like saying "I never wear my seatbelt and never been injured."
But I still don't treat my water...though I am selective.
I do often wonder if you can build up an immunity to the nasties by being exposed to them and building antibodies or whatever...
[QUOTE=Colter;1335869]There are a few studies linked on my blog that are fully downloadable, including the one I am specifically debunking.
QUOTE]
I could't find that one.
[QUOTE=Colter;1335869]There are a few studies linked on my blog that are fully downloadable, including the one I am specifically debunking.
QUOTE]
I could't find that one.
It's a clickable link in the first sentence. (http://bucktrack.blogspot.com/2012/09/backpacker-giardia-debunking-skeptical_8.html) You might have thought it was just a title.
Never mind. Found it.
I like your write up.
But even if one accepts your notion that there is giardia in the backcountry, I am not sure one can conclude that all the different kinds of filters out there -- as used in practice -- really help.
Snowleopard
09-09-2012, 17:55
My impression is that there just isn't a lot of hard data. There is no regular testing of backcountry water. I think the methodology of that paper is not reliable; state health departments just don't seem to have much info on backcountry water sources. Most of the data I've seen is data on municipal water systems. Worcester, MA, some time ago had cryptosporidium in its municipal water. Unfortunately for those who advocate just choosing your water sources carefully, most people would judge the Worcester reservoirs about as good as any water source in southern New England. Other municipal supplies have had giardia in the past.
I suspect that most cases of diarrhea on the trail are bacterial but prevention isn't very different whether it's bacteria or giardia or crypto.
In practice, your water treatment needs to eliminate giardia, crypto, bacteria and, in some places, viruses. You also need to be careful of personal sanitation, by hand washing, dish washing, and being careful with bathroom needs.
Most, but not all, filters will filter out both giardia and bacteria. Giardia and cryptosporidium are harder to eliminate with chemicals (long treatment time, even longer with cold water). In practice, if giardia or crypto are possibilities then a good filter, UV (steripen) or boiling are the best choices, or treat with chemicals for a loooong time. A good combination is a filter plus chemicals (possibly just bleach to kill viruses).
I was not aware that filters work with bacteria.
Never mind. Found it.
I like your write up.
But even if one accepts your notion that there is giardia in the backcountry, I am not sure one can conclude that all the different kinds of filters out there -- as used in practice -- really help.
That might well be true. It's another issue I guess. What I do know for a fact is I made it from 1987 to 2010 treating and being perfectly healthy, and a few weeks after I stopped I had giardiasis! Lots of PCT thru-hikers get giardiasis in the Sierras and it seems that must have some significance.
I'd like to see someone set up a testing program where as many AT and PCT thru-hikers as possible were tested for giardiasis before and after their hikes, and track what types of water treatment methods they used, hygiene habits etc. That would some real data to work with
Stir Fry
09-09-2012, 18:15
I do often wonder if you can build up an immunity to the nasties by being exposed to them and building antibodies or whatever...
10K thats a good question, I have never read anything one way or the other. But I do think it true that those that live in Mexico drink the water and don't seem to get sick but you drink when visiting; "Oh my it on" I wander if that could be the reason?
I'd like to see someone set up a testing program where as many AT and PCT thru-hikers as possible were tested for giardiasis before and after their hikes, and track what types of water treatment methods they used, hygiene habits etc. That would some real data to work with
Just googling for Roland Meuser's study (small though it is) and found it summarized in this:
http://erikschlimmer.com/pdf/GiardiaMyth-Buster.pdf
I have no idea where the truth lies, but think everyone should trust their gut on this.
SouthMark
09-09-2012, 19:03
I do often wonder if you can build up an immunity to the nasties by being exposed to them and building antibodies or whatever...
I have long wondered the same thing. In 38 years I have never treated or filtered my water while hiking and never been sick. Friends that I know that also do not treat their water and have never been sick like me grew up in rural farming country and frequently drank from streams, creeks, rivers and even ponds. Early water supply was wells on the farm. It probably sounds awful but I and others have drank down stream from cows. Of course we could just be lucky but if that is the case for that length of time and types of water sources I have encountered… I need to head to Vegas immediately.
Skidsteer
09-09-2012, 20:10
I have long wondered the same thing. In 38 years I have never treated or filtered my water while hiking and never been sick. Friends that I know that also do not treat their water and have never been sick like me grew up in rural farming country and frequently drank from streams, creeks, rivers and even ponds. Early water supply was wells on the farm. It probably sounds awful but I and others have drank down stream from cows. Of course we could just be lucky but if that is the case for that length of time and types of water sources I have encountered… I need to head to Vegas immediately.
That' my theory as well. I've never known anyone to get giardia that grew up drinking well or cistern water.
No doubt there are exceptions but I haven't found one yet.
GoldenBear
09-09-2012, 20:13
The Katadyn Hiker Pro filters down to 0.3 microns
http://www.katadyn.com/usen/katadyn-products/products/katadynshopconnect/katadyn-water-filters-backcountry-series-products/katadyn-hiker-pro-microfilter/
which will get some bacteria but not viruses, a fact noted by the Center for Disease Control
http://www.cdc.gov/healthywater/drinking/travel/household_water_treatment.html
Skidsteer
09-09-2012, 20:40
That' my theory as well. I've never known anyone to get giardia that grew up drinking well or cistern water.
No doubt there are exceptions but I haven't found one yet.
And thank God I'm a country boy.
Odd Man Out
09-09-2012, 21:06
The Sawyer "point one" filters filter to 0.1 micrometers and filter bacteria.
The Sawyer "point zero two" filters filter to 0.02 micrometers and also filter viruses.
Giardia is a protozoan (neither bacteria nor virus) and will be filtered at a cutoff larger than either of these.
SouthMark
09-09-2012, 21:26
and thank god i'm a country boy.
>>>[like]<<<
Just googling for Roland Meuser's study (small though it is) and found it summarized in this:
http://erikschlimmer.com/pdf/GiardiaMyth-Buster.pdf
I have no idea where the truth lies, but think everyone should trust their gut on this.
It's hard for me to imagine anyone who has taken a thorough rational look at the "Myth-Buster" paper taking it seriously. For example he relies heavily on 1984 numbers in a single place, the high Sierra. The most recent and largest survey in the Sierra found this: [I]bacterial contamination was easily high enough to sicken hikers with Giardia, E. coli and other diseases (http://bucktrack.blogspot.com/2011/03/waterborne-giardia-for-backpackers-no.html) He uses 20 cysts as the "infectious dose" the amount required to make you sick. The FDA says it's one cyst. It's all voodoo math anyway because tests have found water sources loaded with giardia. And the EPA says (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
He says With such self-diagnosis I usually ask, "So, your doctor told you you had giardiasis?" The answer invariably is, "No… I mean, I didn’t get tested –but I’m sure it was Giardia!" People ARE getting tested, myself for example, and the people in this poll (http://forums.outdoorsdirectory.com/showthread.php/94691-Giardia-Poll-Please-vote!/page3), 10% of whom (everyone, not just giardia victims) had had giardiasis confirmed by lab tests.
Schlimmer repeatedly cites Rockwell and Welch, well-known skeptics. I have, I believe, refuted their cited papers. Roland Mueser wrote a great book. His cited water study however has been superceded by a larger and better study already linked to in an earlier post that concluded that both water treatment and hygiene are important.
He says "lab rats don't lie" and then goes on to list numerous hikers and the amounts of untreated water they'd drank without getting sick. Cherry-picked hikers. I could easily list pages of backpackers who've drank untreated water and got giardiasis. He changed the title of his paper which originally had the phrase How Hearsay and Anecdotal Evidence has Created a False Industry Standard It was repeatedly pointed out to him that he included a full page of hearsay and anecdotal evidence.
Anyone taking the time to read through this entire discussion of the Schlimmer paper (http://forums.bowsite.com/tf/bgforums/thread-print.cfm?threadid=380854&forum=36)is bound to learn something. There's theory and then there's reality.
I don't gamble and always treat. Would rather play craps in Vegas than on the trail.
turtle fast
09-10-2012, 10:03
I have suspected for some time that many of the suspected GI illnesses are not giardia, but from factors related to a lack of basic hygene. I have seen way to many hikers not hand washing/sanitizing after using the privy and go right back into preparing their food. I agree with the one pot method and its function to limit bacterial growth via boiling water meals. Further making of boiling water for tea or coffee after a meal makes the function of meal and disinfection even better.
He says With such self-diagnosis I usually ask, "So, your doctor told you you had giardiasis?" The answer invariably is, "No… I mean, I didn’t get tested –but I’m sure it was Giardia!" People ARE getting tested, myself for example, and the people in this poll (http://forums.outdoorsdirectory.com/showthread.php/94691-Giardia-Poll-Please-vote!/page3), 10% of whom (everyone, not just giardia victims) had had giardiasis confirmed by lab tests.
Here is another poll.
http://www.whiteblaze.net/forum/showthread.php?10785-Poll-on-FIltering-and-Illness&highlight=giardia
Not very scientific, but...
handlebar
09-10-2012, 19:27
Been there. Dug 5 catholes in one morning twice. Now I always filter or treat.
Here is another poll.
http://www.whiteblaze.net/forum/showthread.php?10785-Poll-on-FIltering-and-Illness&highlight=giardia
Not very scientific, but...
Thanks for that. Interesting. More scientific than purely anecdotal evidence, no doubt. There are so many things that can skew the interpretation of results. For example, the people most susceptible to stomach ailments are probably the most likely to treat their water in some way. So it's self-selecting. An analogy I've made is that eyeglass wearers often have no better vision than those that don't wear glasses. One could conclude that eyeglasses don't improve vision based on that alone.
Wise Old Owl
09-10-2012, 20:25
Three things....
1 good thread and read!
2 Once you get it, the second time is it not so bad? ( from memory)
3.
[email protected] Guys who have that shingle have to pump out critical papers all the time.
T.S.Kobzol
09-10-2012, 21:04
I have never treated water but I am selective where I drink from. It has worked for the past 38 years. This summer at the insistence of my wife and son we bought the UV lightbulb thingy...and treated during our Long Trail hike, but at some point we ran out of batteries a basically stopped treating for the last 4 days. Either way. No one got sick. I do not advocate this but just throwing it to the mix in this discussion.
Sent from my GT-N7000 using Tapatalk 2
Mountain Mike
09-11-2012, 00:37
I usually treat, normally filter. But it depends on the source. I believe many people do have a built up resistance to pests in the water depending on their background. Vaccines are inert forms of the virus itself to let your system build up antibodies to them. I don't believe everyone that thinks they got giardia on the trail was it as opposed to some other GI illness, but have known several hikers that have had it. Years ago two towns that get water from AT watersheds had outbreaks of giardia in municipal water sources. Pittsfield, MA & Berlin, NH.
The AT normally you can pic & choose water sources, but when you hit other areas when your first water source in 20 miles has cows wading in their own excrement you come to love your treatment choice.
Thanks for that. Interesting. More scientific than purely anecdotal evidence, no doubt. There are so many things that can skew the interpretation of results. For example, the people most susceptible to stomach ailments are probably the most likely to treat their water in some way. So it's self-selecting. An analogy I've made is that eyeglass wearers often have no better vision than those that don't wear glasses. One could conclude that eyeglasses don't improve vision based on that alone.
Is this speculation on your part? I do not recall seeing any evidence which even suggests this is a possibility. If your attempt is to debunk a paper by pointing out potential flaws, one should be very careful to provide evidence and not simply speculation. I am not convinced that your debunking has provided any real evidence that the compilation of sources previously written by many is truly flawed. Yes, you have provided for the possibility, but your arguments are less than compelling. Here is something to chew on, I contacted a published water quality researcher at Paul Smiths college in the Adirondacks to inquire about testing the backcountry water for biological contamination (since the "experts" claim the percentage is contaminated. This researcher was not aware of any studies that have ever been done on the Adirondack backcountry water in regards to biological contamination, specifically giardia, crypto, etc... Thus, your usage ofthe the experts who state that ___% of the water is contaminated are not speaking with data based authority, at least for backcountry water. That said, I will never tell someone how they should deal with their water procurement.
Lone Wolf
09-11-2012, 07:29
i grew up on city water. i never treated or filtered water from georgia to maine. 5 AT completions plus 6000 "other' miles. never got sick. i drank from beaver ponds even. i just added grape kool-aid to make it taste better. "getting" giardia is more hype than anything
russb: Is this speculation on your part? I do not recall seeing any evidence which even suggests this is a possibility.
You are referring to this line in my comments: "For example, the people most susceptible to stomach ailments are probably the most likely to treat their water in some way. So it's self-selecting."
First of all, that's not part of my rebuttal of the paper. It is simply an educated guess stated on this forum based on common sense and statements like this from a single thread on the topic (http://forums.bowsite.com/tf/bgforums/thread-print.cfm?threadid=380854&forum=36) These are two quotes. There are more.
After that experience I never want to go through it again and will always treat or filter the water...I would NEVER think about drinking untreated water from any unknown source. The consequences just arn't worth it
Yeah, so the people saying they wouldn't filter their water and ignore the warnings from the "conspiring communist" government have NEVER had a real case of Giardia. I guarantee you that. If you have had it, (See my earlier post) you wouldn't care if there was a 1 in 10,000 chance of getting it. Especially, when it is so easy to filter your water.
russb: I am not convinced that your debunking has provided any real evidence that the compilation of sources previously written by many is truly flawed.
Actually, I did. To debate this seriously you need to give some examples of where my reasoning and research is in error.
russb: Thus, your usage of the the experts who state that ___% of the water is contaminated are not speaking with data based authority, at least for backcountry water
So you say that that guy said that he was unaware of any studies and from that you draw a scientific conclusion? The EPA says (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 Even in the Rockwell paper he admitted there was giardia in about 1/3 of the water sources in the study he sourced. Sorry, but it's clearly data based.
i grew up on city water. i never treated or filtered water from georgia to maine. 5 AT completions plus 6000 "other' miles. never got sick. i drank from beaver ponds even. i just added grape kool-aid to make it taste better. "getting" giardia is more hype than anything
What took you so long lone wolf? You wouldn't think it's hype if you got a bad case, I guarantee you that. I cited two scientific papers that showed many people got giardiasis on their first trip out. I know lots of old timers who've never gotten it at all. Lots of them that don't think they have it are asymptomatic carriers.
I don't care if people treat their water or not. I do care if they have enough facts to make a rational evalutation of the potential risks and consequences.
Feral Bill
09-11-2012, 12:55
i grew up on city water. i never treated or filtered water from georgia to maine. 5 AT completions plus 6000 "other' miles. never got sick. i drank from beaver ponds even. i just added grape kool-aid to make it taste better. "getting" giardia is more hype than anything No doubt true, but as anecdotal evidence from one person not especially relevant to risk analysis. The research to find out real risk wouldn't be especially complicated, but probably costly in time, effort and lab tests. Maybe this is the "college credit for hiking" opportunity people are looking for.
No doubt true, but as anecdotal evidence from one person not especially relevant to risk analysis. I am not so sure.Lone Wolf took samples from well over 1000 different water sources over the miles he has walked. Seems to me that is a statistically valid sample size.Depends what the hypothesis is, I suppose.Here is a thought to ponder. Plenty of people have and will continue to report exactly what water source have them giardiasis. Has anyone ever shared with the larger community what failure of basic hygiene made them sick? I can't remember one. Why is that?
Mr. Colter, I am not debating, only letting you know that I find your self-proclaimed debunking quite lacking. Head to head, the papers to which you are attempting to refute are more compelling than your arguments.
I am not so sure.Lone Wolf took samples from well over 1000 different water sources over the miles he has walked. Seems to me that is a statistically valid sample size.Depends what the hypothesis is, I suppose.Here is a thought to ponder. Plenty of people have and will continue to report exactly what water source have them giardiasis. Has anyone ever shared with the larger community what failure of basic hygiene made them sick? I can't remember one. Why is that?
If x% of people do not show symptoms of Giardia and Lone Wolf is part of that group then his not showing symptoms from 10 or 10000 water sources would not be reason to state that the water sources are free of Giardia.
Usually it's hand washing that causes the largest percentage of bacterial/viral/cyst/parasite illness. Next would be drinking water.
Mr. Colter, I am not debating, only letting you know that I find your self-proclaimed debunking quite lacking. Head to head, the papers to which you are attempting to refute are more compelling than your arguments.
The whole point is to get to the science of the matter. My blog post clearly spells out how those famous papers made a long list of verifiable mistakes which refutes their conclusions. You haven't identified any mistakes in my rebuttal.
"I don't want to debate it but you're just wrong" doesn't carry any weight in science.
If x% of people do not show symptoms of Giardia and Lone Wolf is part of that group then his not showing symptoms from 10 or 10000 water sources would not be reason to state that the water sources are free of Giardia. .
OK.
Colter's report did say that 66% of us don't get any symtoms even we get Giardia.
Three things....
1 good thread and read!
2 Once you get it, the second time is it not so bad? ( from memory)
3.
[email protected] Guys who have that shingle have to pump out critical papers all the time.
Thanks! Apparently some people build up a resistance but for myself and some others I know of that has not been the case. I got sick the worst the last time.
The whole point is to get to the science of the matter. My blog post clearly spells out how those famous papers made a long list of verifiable mistakes which refutes their conclusions. You haven't identified any mistakes in my rebuttal.
"I don't want to debate it but you're just wrong" doesn't carry any weight in science.
I will not identify the long list of logical fallacies and errors embedded within your blog. Someone as learned as yourself should be able to find them by himself.
You are not conducting science you are writing to persuade. I am letting you know that your persuasion was not adequate in convincing me. Happy hiking.
I will not identify the long list of logical fallacies and errors embedded within your blog. Someone as learned as yourself should be able to find them by himself.
You are not conducting science you are writing to persuade. I am letting you know that your persuasion was not adequate in convincing me. Happy hiking.
Some would interpret that as "I cannot find any logical fallacies and errors."
"You are wrong and I'm letting you know" does not constitute a rational response. Certainly not a scientific one.
Some would interpret that as "I cannot find any logical fallacies and errors."
"You are wrong and I'm letting you know" does not constitute a rational response. Certainly not a scientific one.
Ok.
post hoc
misleading vividness
straw man
just for starters.
again, you are not engaged in science but research and writing to persuade. I would think you wanted to be successful in that endeavor. Knowing you werent at least in one case would suggest that the writer might consider their argument was lacking. Of course arrogance often obscures this likelihood.
...you are not engaged in science but research and writing to persuade. I would think you wanted to be successful in that endeavor...
I am trying to persuade, by analyzing scientific papers and arguing the facts.
You are trying to persuade by saying I'm wrong and using ad hominem attacks.
And you accuse me of not using science?
A couple of days ago I got an email from a physician who had recently written a skeptical article on the topic and he said that after reading my post he is reconsidering his position. Doesn't make make me right, but it does show that some people are taking it seriously, even if you're not.
FlyPaper
09-12-2012, 12:30
I don't gamble and always treat. Would rather play craps in Vegas than on the trail.
Gamble or not, water I filter with my 0.2 micron filter TASTES GREAT! Water I treat with a Steripen (which I presume is
the same as it would taste untreated), generally does not.
Feral Bill
09-12-2012, 23:18
Consider this- http://youtu.be/qudvQaIogw0
Feral Bill
09-12-2012, 23:23
Consider this: http://youtu.be/qudvQaIogw0
Sorry for the double post