I am researching giardiasis (maybe I'm obsessed, but I have a personal interest!) I have found several studies showing that people are getting giardiasis from backcountry water:
Giardiasis in Colorado: an epidemiologic study

An outbreak of giardiasis in a group of campers
Factors associated with aquiring giardiasis in British Columbia residents

I've seen convincing studies showing most backpacker stomach upsets are hygiene related, but I've been unable to find studies showing backpacker GIARDIASIS infections stem from poor hygiene. I have no doubt that many cases are the result of poor hygiene, but I'd like to find studies showing that's the case. Hopefully studies similar to the ones cited above.

Can anyone help me out with links and quotes?

Hmmmm. Going on an overnight in RMNP in two weeks. Guess I'll be sure to treat the water!

Have you looked there? Google Scholar isn't a perfect database by any means, but it has a fair amount of peer reviewed studies/reviews linked in. Acquiring full-text .PDFs is another matter, of course.

Thanks Harrison, excellent tip. I'd Googled my brains out but there was a whole lot of chaff to sift through. Google Scholar really helps cut through it. I'm not finding specificallly what I'm looking for but I've already found really interesting stuff I hadn't seen before. For example:

Heating in Water-Experiments conducted with cysts of
G. lamblia and of G. muris indicated that the two species
have virtually the same sensitivity to inactivation by heating.
Cysts of both species were completely inactivated by heating
to 70°C [158 F.] for 10 minutes. Heating to 50°C and 60°C for 10
minutes produced 95 and 98 percent inactivation, respectively
(Figure 3). http://ajph.aphapublications.org/doi/pdf/10.2105/AJPH.79.12.1633

Not the point of your thread, but interesting that some chlorine wasn't that effective.

Begs several questions - what about chlorine dioxide and hollow fiber filters.

What about a higher temperature for a shorter time - like what I do when I bring water close to a boil to redhydrate food - several minutes to get up to 90 C or so.

Good to see you find Google Scholar useful. If you're really ambitious, you might find getting into PubMed (the National Library of Medicine's database) productive. You should be able to search through it via a university library's website (i.e., Alaska-Anchorage). You won't be able to access full-text articles, but should be able to read abstracts. PubMed is amazingly broad and current.

BTW, the bit about water temperatures fits with what I've read in the past-- that "boiling" water is something of a safe precaution when it comes to giardia-- and that "hot" water is often sufficient (but not always, as you can tell from your stats).

Edited by carpenh on 09/08/2012 08:44:22 MDT.

That "original" paper in your second link is thought to be wrong, as discussed in first link below.

http://download.journals.elsevierhealth.com/pdfs/journals/1080-6032/PIIS1080603204704986.pdf

http://onlinelibrary.wiley.com/doi/10.2310/7060.2004.13621/pdf

Edited by jshann on 09/08/2012 11:36:03 MDT.

Welch is, in my opinion, guilty of some serious confirmation bias.

For example, that paper he tried to debunk, where he says they never found any cysts so how could it be giardia? What he does not mention is that the filter design they were using to determine if there were cysts present in the stream DID NOT WORK! Seriously. He is all over the internet quoting himself, but his work, in my opinion, does not stand up to a close look. I just finished a blog post debunking one of the Welch giardia papers, including the aforementioned "oversight." I would appreciate any of you here, especially those with a science or medical background, to read through what I wrote and critique it in the comments, because I want it to be logical and correct.

The second paper you cited is my idea of a scientific paper, letting the evidence lead where it will. Thanks for the link. But it deals with gastrointestinal illness in general and not giardiais specifically and I think the two are often confused in the debate.

Edited by Colter on 09/08/2012 18:58:58 MDT.

Welcome home Colter! I'm sure you have seen this article. http://www.modbee.com/2010/05/08/1158938/fouled-waters-sierra-lakes-streams.html. I my mind it brings together the two sides quite nicely especially when looking at the Sierra. There are quite a few giardiasis cases in Mammouth which makes perfect sense. I'm sure you can remember the cow infested areas of the southern Sierra which would be 10-14 days prior to Mammouth. The researcher quoted in this article may have some great data on the subject.

Thanks Greg! Those of us who've had giardia tend to have a more conservative view on things, don't we?

This is a pretty telling quote from that article you linked to: [in places] bacterial contamination was easily high enough to sicken hikers with Giardia, E. coli and other diseases

That's the point, isn't it? Most of the water is OK to drink, but some of it isn't. You can't know until after it's been tested in a lab. Or by your stomach, when it's too late.

Did you see this quote from an emergency room doc:
"Several backpackers appear weekly at Centinela Mammoth Hospital in Mammoth Lakes sick enough with giardiasis to need urgent care."

That's where I've been treated after drinking water that I can't get giardia from. ; )

Welcome home Colter! I'm sure you have seen this article. http://www.modbee.com/2010/05/08/1158938/fouled-waters-sierra-lakes-streams.html. I my mind it brings together the two sides quite nicely especially when looking at the Sierra. There are quite a few giardiasis cases in Mammouth which makes perfect sense. I'm sure you can remember the cow infested areas of the southern Sierra which would be 10-14 days prior to Mammouth. The researcher quoted in this article may have some great data on the subject.