gdurkee wrote:Wait, wait, wait there Dr. Science
It seems like that would qualify as snide. What do you think?
Your opinionthe Sierra, even in cattle areas, just doesn't get many cases of giardia.
vs a Sierra physician's experienceSeveral backpackers appear weekly at Centinela Mammoth Hospital in Mammoth Lakes sick enough with giardiasis to need urgent care
I know for sure what at least one more Sierra physician thought about the Rockwell paper when I asked. He laughed.
In that Colorado incident, they did determine it was from the water, Although the epidemiologic data and fecal coliform counts implicated the remote mountain stream used as water source by the group as the vehicle of transmission, Giardia lamblia cysts were not recovered from stream water.
I researched this and found out that the type of test filter being used didn't work, so that's the expected result if there was giardia in the water.
There was a second study, too: http://download.journals.elsevierhealth ... 711729.pdf
In that study, 2 of 35 people got Giardia, but were asymptomatic. A third had Giardia symptoms, was treated for Giardia, and quickly recovered. Giardia is often not detected with a single test. So it is certain at least 5.7% got Giardia, and it seems more than likely that 3 of 35 got Giardia, for a total of 8 1/2%. About 1/2 to 2/3 of the time people ARE asymptomatic, so that's no surprise.
You said Following up with that source you find that 2%/single cyst stuff is extrapolated and refers to infection (carrier) not symptoms
Again, Rockwell did his risk calculations based on NO risk from 1-9 cysts. He is absolutely wrong on that and it significantly understates the risk, probably by more than an order of magnitude.The only study on infectious dose is the Rendtorff study. Different strains of giardia have dramatically different levels of infectivity. One thing I dug up is a quote from Rendtorff himself saying that they hadn't even determined if the cysts were viable. In other words, it's perfectly possible that ALL the men that didn't get giardia had no chance of getting it. The results HAVE to be extrapolated because the testing was so minimal. The only thing it determined for sure is that it proved the infectious dose is very low. To the best of my knowledge only five people in history have been tested below the ten cyst level, and that was one time with a single cyst each, a cyst that may have been dead to begin with.
Derlet's findings clearly refute Rockwell's drink freely and confidently.
Again the biggest retrospective study (what actually DID happen) ever done on the subject concluded drinking untreated mountain water is an important cause of endemic infection. http://www.journals.elsevierhealth.com/ ... 105_330%20
I talked to the experts at San Francisco Department of Public Health today about giardia in their water. They said the giardia counts were for raw water.
Here's how people are reading the Rockwell paper SanFrancisco water has more Giardia than Sierra...Hetch-Hetchy (One of San Francisco's Water Supply's) in not filtered at all.
Except for the water treatment plant that Rockwell doesn't mention. http://www.thebackpacker.com/trailtalk/ ... 380,-1.php