Re: Why Rockwell is Wrong about Giardia
Posted: Thu Feb 21, 2013 1:40 pm
Interesting points re: Bob's article. It's worth noting that it was a literature review, summarized results and presented conclusions based on that. I talked to him fairly extensively about it after he first published it and I picked it up for Sierra Nature Notes. I thought it a very good effort and article on the subject and still think so.
That said it's, what?, 15 years old now. Definitely time for rethinking some of the conclusions presented. I'm also a little bothered that discussing stuff that appears previously is somehow an error in forum etiquette. Topics slide off the front page and are buried. New people come on board who could benefit from discussions held even a year ago. So on that point, I think a discussion or re-re-re discussion is worthwhile. The only thing I'd object to is obvious baiting or trolling, which is not the case here (though he edges close with the provocative -- and misleading -- title. Bob wasn't "wrong" -- it was a literature review. His conclusions from the existing studies and science were correct, certainly defensible).
There's no question that some people are incredibly susceptible to giardia -- the OP is an obvious example. As such, he should definitely treat everything. Obviously I talk to a lot of people who hike and have been doing so before and after water treatment became so widespread. In all those years -- probably over 10,000 people -- I've talked to only a handful of people diagnosed with giardia. No question it's nasty when you get it, but I'm not convinced it was ever that prevalent in the Sierra. There's not much difference in the number of people who have said they've had infections before or after the late 80s (?) when treatment became widespread.
I do think that simple hand washing among groups probably gets rid of a significant percentage of infections -- this is certainly the case in day care (cleaning toys etc. daily). But many mammals carry the cyst that can infect humans and so it's definitely in the water supply (belding ground squirrels have a very high infection rate, but it's not the same type that humans are susceptible to...)
But! Studies of cattle show a high percentage of cows carry the cysts -- especially calves. There's also a study from Yosemite that showed about 3 - 6% of horses out of Tuolumne carried giardia cysts (and about the same percentage carried Cryptosporidium parvum).
If I were a PCT hiker coming up through Kennedy Meadows, I would absolutely treat. Same going north through any USFS areas where cows are prevalent. But I also think there's very low risk for most people hiking in either Yosemite and Sequoia Kings. I carry a steri-pen now and do use it in high-use areas when I don't know of a side-stream or spring around.
g.
That said it's, what?, 15 years old now. Definitely time for rethinking some of the conclusions presented. I'm also a little bothered that discussing stuff that appears previously is somehow an error in forum etiquette. Topics slide off the front page and are buried. New people come on board who could benefit from discussions held even a year ago. So on that point, I think a discussion or re-re-re discussion is worthwhile. The only thing I'd object to is obvious baiting or trolling, which is not the case here (though he edges close with the provocative -- and misleading -- title. Bob wasn't "wrong" -- it was a literature review. His conclusions from the existing studies and science were correct, certainly defensible).
There's no question that some people are incredibly susceptible to giardia -- the OP is an obvious example. As such, he should definitely treat everything. Obviously I talk to a lot of people who hike and have been doing so before and after water treatment became so widespread. In all those years -- probably over 10,000 people -- I've talked to only a handful of people diagnosed with giardia. No question it's nasty when you get it, but I'm not convinced it was ever that prevalent in the Sierra. There's not much difference in the number of people who have said they've had infections before or after the late 80s (?) when treatment became widespread.
I do think that simple hand washing among groups probably gets rid of a significant percentage of infections -- this is certainly the case in day care (cleaning toys etc. daily). But many mammals carry the cyst that can infect humans and so it's definitely in the water supply (belding ground squirrels have a very high infection rate, but it's not the same type that humans are susceptible to...)
But! Studies of cattle show a high percentage of cows carry the cysts -- especially calves. There's also a study from Yosemite that showed about 3 - 6% of horses out of Tuolumne carried giardia cysts (and about the same percentage carried Cryptosporidium parvum).
If I were a PCT hiker coming up through Kennedy Meadows, I would absolutely treat. Same going north through any USFS areas where cows are prevalent. But I also think there's very low risk for most people hiking in either Yosemite and Sequoia Kings. I carry a steri-pen now and do use it in high-use areas when I don't know of a side-stream or spring around.
g.