POP QUIZ

Hi Buck

> There's a reason physicians often ask "Have you been camping? Did you drink any
> untreated water?"

The reason may be that they learnt this question in med school. Nothing more. Just following rote learning.

The number of people who get giardia from kids at play school is KNOWN to be huge. The number of people who report suspected giardia after going backpacking is tiny in comparison.

Cheers

> Let''s take it as fact that Giardia can pass through the nose to infect.
Why????
Frankly, I think it is a rather silly idea. It has no realistic mechanism.

> As a solo hiker, many of the potential human related causes go away.
Some do go away of course, but the biggest ones remain: lack of personal hygiene and contaminated water.

Cheers

Here's a nice 5-yr study published in the peer-reviewed journal Wilderness and Environmental Medicine that examined water sources throughout the Sierra…a place frequently cited as spore-free (or nearly so).

My first trip to the Sierra in August was for the JMT…and wow did I see a lot of pack animals. And according to this study, just shy of cattle it was the most common area to have giardiasis contamination. It's an interesting read…

http://www.ericjlee.com/Articles/Sierra%20Water%205years.pdf

And not meaning to bring up an old argument, but seriously – does anyone have any good scientific, peer-reviewed data that says drinking untreated surface water in the wild is NOT a risk for giardia?

No peer reviewed journal papers, just my own humble experience of not treating about 75% of the water I drink in the Sierra. But this is water typically above treeline, away from trail and pack animals, and off the beaten path of most people. If I can see the source, I typically drink without treating.

"Let''s take it as fact that Giardia can pass through the nose to infect.
Why????
Frankly, I think it is a rather silly idea. It has no realistic mechanism."

As a primary source? No probably not. As a potential source? Doubtful but sure. If for some reason you stick your contaminated finger three knuckles deep into your nostril to self administer the vulcan brain massage, then do the good ol' "snnnooorrrt….. haaaaaaaaaaaawk….. (gulp)", then the now giardia contaminated booger would be routed to the stomach in lieu of the lungs.

Author's note: After a quick test, I'm only capable of going one knuckle deep for vulcan brain massage purposes but from what I've seen sitting at a red light, many of my fellow citizens are capable of digging much further.

Have we learned anything here other than that following good field hygiene practices and treating/filtering water are generally recommended to prevent beaver fever?

It'd be nice to hear Colin Crusor's (pretty sure I just screwed up his last name) opinion on the matter has he seems to be the resident expert. I'll try to find some of the other threads that he's commented in but if memory serves, giardia is capable of changing its antigens which affects the human bodies ability to develop a resistance to it.

Yep…. screwed Colin Krusor's name up. Some of his previous comments:

"Giardia have a trick called "antigen shifting". Giardia has a repertoire of more than 200 "variant surface proteins" and individual Giardia cells are constantly changing the ones that are on their surface at any given time so your immune system will never be able to recognize them as something it has seen before. There is a Giardia vaccine in development that uses whole inactivated Giardia cells that have been genetically manipulated so all of their protein wardrobe is on the surface at once. This is not likely to confer perfect immunity but it will get one's immune system better acquainted with more of Giardia's disguises, so it is more likely to recognize new Giardia cells as pathogens."

and http://www.backpackinglight.com/cgi-bin/backpackinglight/forums/thread_display.html?forum_thread_id=78686&skip_to_post=671000#671000

" have no desire to be alarmist, but I think it is important to note that Crypto and Giardia are the best known eukaryotic parasites in surface waters but not the only ones.

I study the protozoan parasite Toxoplasma. Toxoplasma oocysts cannot be killed by any chemicals that are safe to drink. After 24 hours in 6% bleach (twice the strength of the stuff in the bottle at a drug store) they are 100% viable and readily cause fatal infections in mice. In my lab, we store viable Toxo oocysts in sulfuric acid. Many human infections have been reported from ingestion of water contaminated with this parasite. In 1995, about 400 people in Victoria, BC became infected from municipal tap water (which was chlorinated). Subsequent research found that the source was toxoplasma-infected mountain lions living in the areas around the municipal reservoir. The parasites were being transported in the watershed. In some areas in California, the proportion of the mountain lion and bobcat population that has the infection approaches 80%. In humans, toxoplasmosis (like cryptosporidiosis) is typically a long-term subclinical infection following an initial bout of GI symptoms. However, it has also been implicated as a risk factor for schizophrenia and cognitive changes, and it is a serious risk to a fetus if a woman becomes infected while she is pregnant.

Cysts of eukaryotic parasites (worms and protozoans) are probably in all backcountry surface waters (excluding direct snowmelt) because they are shed in huge numbers by many wildlife species and (in contrast to bacteria and viruses) they accumulate because they are extremely tough and remain viable for months or years in water and soil. Polyparasitism (concurrent infection with multiple parasites) is certainly the norm in people in many developing countries now, and it was probably the norm among people in the US until about a century ago. On the American frontier, everyone probably had parasites, and people who continue to drink untreated water when backpacking probably have them as well.

In remote alpine areas with fast-moving streams (at the top of the watershed), the risk from pathogenic bacteria or viruses is minimal, so a large pore filter (like the Frontier Pro) is enough by itself, in my opinion. In areas lower down on a watershed, but still remote, a small pore filter (<0.3 microns) is probably adequate by itself (removes worm eggs, protozoa, and most bacteria). In lowland or coastal areas, or areas regularly used by other hikers or domestic animals, it seems to me that there are only three good options: boiling, steripen treatment, or a combination of filter+chemicals. In these higher-risk places, filters alone are risky because they don't remove viruses or small bacteria (ie, Lepto, Brachyspira, etc.), and chemical treatment alone is risky because it won't inactivate some protozoa.

I use a Sawyer Squeeze or a Sawyer gravity filter and carry Aquamira tabs. I can use the Sawyer alone in remote alpine places (and I have the Aquamira tabs in case the Sawyer freezes), and in lowland places I use both (and wait 30 minutes)."

"> Let''s take it as fact that Giardia can pass through the nose to infect.
Why????
Frankly, I think it is a rather silly idea. It has no realistic mechanism."

Well, not really. It actually does have a mechanism, Roger. Your nose and the rest of your mucus membranes are connected directly to your stomach and help reduce the effect of the acids, enzymes used in digestion. Most of the secretions end up in the stomach…hence your mechanism. You ingest mucus from your mouth and nose as a way to recycle salts, proteins, etc, and this is a normal part of breathing. One purpose is to protect the fragile lungs by directing contaminants to the more rugged digestive system, and, out of the body.

Jennifer said: does anyone have any good scientific, peer-reviewed data that says drinking untreated surface water in the wild is NOT a risk for giardia?

I know of only one peer-reviewed paper saying there is little evidence people are contracting giardia from backcountry water. Giardiasis as a threat to backpackers in the United States: a survey of state health departments It is an extremely misleading and poorly designed paper. The CDC has specifically refuted Welch’s conclusions. Welch is the source of most of the skeptical “science.”

Hi James

> Your nose and the rest of your mucus membranes are connected directly to your stomach
Yes, but at a molecular transport level. I seriously doubt the transport mechanism is able to cart 10 micron cysts along all the way to the stomach!

> You ingest mucus from your mouth and nose
OK, that is possibly viable. But to say it is the top route for infection, greater than contaminated hands and water? Ummm…

I say again: show me the published research to support this claim. I am always open to convincing proof.

Cheers

I wish I could find it.

Then again, an article a person puts out is just their interpretation of the facts they came up with.
It is not the end all be all of what may or may not be the truth.

Roger, I think you must've missed that day in anatomy class. I knew this in fourth or fifth grade, part of basic human systems. Much much more than molecular transport, cilia move mucus, dust, etc, up and out the lungs, down out of the sinuses to the back of your throat. Then you swallow…you breath from either/both your mouth and nose.

Washing up with untreated water is enough to spread cycts all over your body, into your nose and eyes and onto your lips. A simple splash will potentially infect you exactly the same as a sneeze will spread a cold.

Now, "primary"…well, it depends on the environment. I think it is very misleading to think of a primary avenue of infection without thinking of where that infection origonates. Hiking solo or with your mate, it doesn't much matter. You cannot catch stuff from yourself or from your wife. I think you cannot even infect yourself with E. coli however, several medical people I have checked with don't know. Anyway, this stuff is all part of social diseases or from your enviornment. Enviornmental concerns are varied. How do you say water is the primary vector when there is none and you have to carry it all? Beaver transmit gardia. How did they catch it? Are they naturally immune or asymptomatic? And so on… "Primary" depends on what you are looking at. Yes, the pop quize is valid sometimes…probably under most conditions…since it *must* be in your stomach/intestine to start making you sick, therefore it *must* pass through your mouth/nose/eyes at some point. The other end is all outgoing and not much of a concern.

But, looking at how it got into/onto your mouth, nose and eyes (hence into your stomach) is another story. To say most people catch it from going backpacking is largly a falicy (because most backpackers know enough to avoid it.) People who take day hikes across streams, or go swimming in wild water are probably much more at risk. Here in the NE corner of the USofA, I avoid "iffy" looking water without boiling or treating. Spring water, I have been drinking for 60 years, despite most being closed down, in recent years due to gardia. Spring water (with brook trout swimming around in the spring box) was our ONLY source of water when I grew up in the Catskils. Canoeing across "swampy" water never brings about bouts of diahrea. Why? I surely splash around enough, up to and including splashing my face and arms to cool off. I don't worry about it.

Does anyone know if getting sick with gardia confers any sort of immunity or perhaps asymptomatic infection thereafter? Lots of questions, more than simple "primary" or number 1 way (and how) of catching gardia. That is always the ingestion of cycts/protists.

James,

I quoted Colin's answer to the immunity question a few responses ago. Best I can tell, he's the resident SME on the topic.

Hi Colin, if you're reading, i'm curious about an old quote of yours, "I study the protozoan parasite Toxoplasma. Toxoplasma oocysts cannot be killed by any chemicals that are safe to drink. After 24 hours in 6% bleach (twice the strength of the stuff in the bottle at a drug store) they are 100% viable and readily cause fatal infections in mice."

Has there been any research on whether UV light (as per Steripen or the like) is effective against such parasites?

Sorry Ian, I missed that. It makes sense, though…

> Has there been any research on whether UV light (as per Steripen or the like) is
> effective against such parasites?

Yes. For example:

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2916465/
August 2010

The effect of UV exposure on Toxoplasma gondii oocysts has not been completely defined for use in water disinfection. This study evaluated UV-irradiated oocysts by three assays: a SCID mouse bioassay, an in vitro T. gondii oocyst plaque (TOP) assay, and a quantitative reverse transcriptase real-time PCR (RT-qPCR) assay. The results from the animal bioassay show that 1- and 3-log10 inactivation is achieved with 4 mJ/cm2 UV and 10 mJ/cm2 low-pressure UV, respectively. TOP assay results, but not RT-qPCR results, correlate well with bioassay results. In conclusion, a 3-log10 inactivation of T. gondii oocysts is achieved by 10-mJ/cm2 low-pressure UV, and the in vitro TOP assay is a promising alternative to the mouse bioassay.
(My bolding)

http://cfpub.epa.gov/ncer_abstracts/index.cfm/fuseaction/display.abstractDetail/abstract/1128/report/F
(This covers viruses, bacteria, protozoa and indigenous spores. Cost: $524,848)

Protozoa. The inactivation of G. lamblia cysts by low pressure UV irradiation was determined using a gerbil infectivity test. Reduction of G. lamblia infectivity was very rapid, reaching a detection limit of greater than 4 log within a dose of 1 mJ cm-2. The ability of UV-irradiated G. lamblia cysts to repair UV-induced damage following UV doses of 16 and 40 mJ cm-2 also was investigated, and there was no phenotypic evidence of either light or dark repair of DNA damage caused by low pressure UV irradiation of cysts at the UV doses tested.

The UV inactivation of T. gondii was carried out with the assistance of Dr. Dubey at the U.S. Department of Agriculture and Dr. Simmons at the University of North Carolina at Chapel Hill. T. gondii oocysts were thought to be resistant to UV disinfection although extensive studies had not yet been performed. Using a mouse infectivity test protocol carried out by Dr. Dubey, the inactivation of T. gondii with UV irradiation was found to be very effective. Using low pressure UV a 4-log reduction in infectivity was achieved at a UV dose of approximately 8 mJ/cm2 in reagent water, with similar findings in natural water tests. Polychromatic UV irradiation from a medium pressure UV system provided a similar level of inactivation. Thus in addition to the known effectiveness of UV toward Cryptosporidium oocysts and Giardia cysts, UV is very effective for inactivation of Toxoplasma oocysts at low UV doses.

Cheers

Hi James

> Much much more than molecular transport, cilia move mucus, dust, etc, up and out
> the lungs, down out of the sinuses to the back of your throat. Then you swallow …
Ok, point made, but that is a very long pathway compared to a contaminated finger in the mouth!
To be honest, while I knew about the cilia transport, I had discounted it as improbable.

Cheers

Wow, one millijoule per square centimeter! More power!

Whip out the slide rules!

–B.G.–

Thanks for the info on the UV. Looks like the Steripen will work.