Cleanliness of Lakes?

[franklin411]

INFECTIOUS DOSE: Less than 10 cysts when given orally, may even be as low as 1 cyst

https://www.msdsonline.com/resources/ms ... a-lamblia/

[apeman45]

I read somewhere that the risk is lower from the surface of lakes than in streams. The reason being that UV rays from the sun kill guard near the surface while streams have everything mixed up. Of course taste from lakes is often not as good as running water and with all the easy filtering options why risk it. I've swum in A LOT of Sierra Lakes and have not contracted giardia yet. It is not something worth worrying about for me.

[kpeter]

If giardiasis were as serious as cancer, then the obsession with preventing it would be warranted. But the symptoms, while highly unpleasant, do not appear to have any serious long term consequences other than (perhaps) making someone lactose intolerant. Once diagnosed it can often be treated with a single dose of tinidazole. And--for most people--it appears to be somewhat difficult to contract in the high Sierra.

In short, while it makes sense to follow some precautions, the threat should be kept in perspective. On the long list of wilderness worries it should be pretty low.

[dave54]

A little additional for AT's comment, and LNT in general.

The 200 foot rule is not from the current water edge, but the high water mark. Late in the year the water edge is a lot lower, and in some cases 200 feet is still within the lake bed. When the lake fills next Spring, the waste you dutifully dumped a good safe distance away will leach into the water.

[limpingcrab]

Ya, in popular places like Rae Lakes loop there's a nice oily sheen in some of the downwind bays, supposedly from stuff coming off of people's clothes and skin.

As to getting sick, I'd bet permanent banishment from the Sierra that using lake water to rinse clothes and yourself won't get you sick. Like SSSdave, I've drank from many lakes and streams without filtering or getting sick (your results may vary)

[franklin411]

Some people infected with giardia never show any symptoms. And if left untreated, some people's immune systems will clear the infection entirely, but others will harbor the bug forever. *They* won't get sick themselves, because their bodies are used to the new companions. But since they have a live infection, they'll still pass giardia cysts to the environment or others--up to 10 billion cysts per day. The giardia infection rate for the US is 2-10% (adults:kids). It's 33% for the third world.

So, nobody can say for sure whether they haven't had giardia because they could be one of the ones who didn't show symptoms. And even if that makes them "lucky," they can still harm lots of other folks because they're basically giardia factories.

https://www.cdc.gov/parasites/giardia/i ... urces.html

[WarrenFork]

DO NOT wash clothes or use soap in lakes. That's how they become contaminated with chemistry no filter will remove. Take a container of water away from the lake (minimum of 200 feet) and wash off sunscreen etc before doing any swimming. Don't urinate in the lake. Don't urinate near the lake.

Some of the waters in the Sierra are now showing signs that people are urinating too close, or in, the water -- low levels of medications that people take (antidepressants for example) are showing up in the testing that is sometimes done to monitor water purity. Sunscreens and other chemicals are not removed from water by backpacker filters.

As has been pointed out to you more than once on the Backpacking Light forums, you really ought to do your homework on water treatment. The sweeping assertions in bold simply aren't true. The carbon filters employed in devices such as those sold by MSR adsorb many chemical contaminants, including herbicides and pesticides. Where they fail is with high chemical concentrations and heavy metal contamination. Users are advised to avoid water sources such as mining tailing ponds or those near agricultural operations. Few if any lakes in the Sierra backcountry are chemically contaminated to such an extent.

The biological and ethical case for LNT principles is a strong one. There is no need to resort to "alternative facts" in support of it.

[SSSdave]

https://www.health.harvard.edu/diseases ... iardiasis-

snippet:

In developing areas of the world, it is common for more than 20% of a country's population to have ongoing Giardia infection. In the United States, only 1 or 2 out of every 10,000 people have Giardias in a typical year,...Up to two-thirds of people infected with the organism do not have any symptoms.

What isn't related is the majority of those without symptoms are residents of the third world where they they catch disease as children and develop immunity so. Not the same here in the USA but don't have a link at the moment. One is most likely to catch giardiasis from some fast food worker that used the restroom and then because no one else was there to see him, did not wash his hands before making that cheeseburger you ate. If a person long term does not have even mild gastrointestinal issues like gas, then they are also unlikely to be your symptom-less carrier.

Wikipedia snippet:

...Person-to-person transmission accounts for the majority of Giardia infections and is usually associated with poor hygiene and sanitation. Giardia is found on the surface of the ground, in the soil, in undercooked foods, and in water, and on hands without proper cleaning after handling infected feces.[30] Water-borne transmission is associated with the ingestion of contaminated water. In the U.S., outbreaks typically occur in small water systems using inadequately treated surface water. Venereal transmission happens through fecal-oral contamination. Additionally, diaper changing and inadequate hand washing are risk factors for transmission from infected children. Lastly, food-borne epidemics of Giardia have developed through the contamination of food by infected food-handlers.

[freestone]

Published reports of confirmed giardiasis among outdoor recreationalists clearly demonstrate a high incidence among this population. However, the evidence for an association between drinking backcountry water and acquiring giardiasis is minimal. Education efforts aimed at outdoor recreationalists should place more emphasis on handwashing than on water purification. Further studies should attempt to separate the specific risk factor of drinking water from backcountry sources from other behaviors among this group that may contribute to the risk.

https://www.ncbi.nlm.nih.gov/pubmed/10737847

So, you filter your water religiously but do not wash your hands properly? Hmmm...

Wet your hands with clean, running water (warm or cold) and apply soap.
Rub your hands together to make a lather and scrub them well; be sure to scrub the backs of your hands, between your fingers, and under your nails.
Continue rubbing your hands for at least 20 seconds. Need a timer? Hum the "Happy Birthday" song from beginning to end twice.
Rinse your hands well under running water.
Dry your hands using a clean towel or air dry them

https://dchealth.dc.gov/page/hand-washing-fact-sheet

[maverick]

Really, aren't there enough threads on this already on HST, OP please use the "search" feature, and all over the internet, here are just a few of over a dozen::

viewtopic.php?f=1&t=18546&p=137697&hili ... ia#p137688
viewtopic.php?f=1&t=3842&hilit=giardia#p22784
viewtopic.php?f=9&t=8954&hilit=giardia#p66123
viewtopic.php?f=1&t=7016&p=49230&hilit=giardia#p49203
viewtopic.php?f=9&t=8933&hilit=giardia
viewtopic.php?f=15&t=7490&hilit=giardia#p53499