Giardia: Just the facts m’am

Controversial topic. I've read what you just posted at other times also and I'm sure it makes sense…although there's a ton of people who don't wash their hands in the city after having a BM and you'd think they'd spread giardia then as well? Perhaps they do and that explains what people write off as a stomach flu.

I know people that drink straight from the source w/o purifying and they don't get sick. The water is probably ok. But having heard about how awful the symptoms are of giardia and crypto, I have always boiled. I'm old school and continue to boil since I like a hot breakfast and dinner anyway, rather than carry a filter. I do have a couple Aquamira tablets for backup. I am careful about hygiene, at all times, however and I'm a germaphobe anyway so I don't let other people stick their hands into my food bags. If they want something, I'll pour it out into their hands.

I have always wondered this about the theory that bad hygiene, not bad water, causes giardia transmission (or other intestinal maladies): are you saying that people give themselves giardia or gi disorders from their own fecal matter? That's what it sounds like to me, but if so, I don't believe that makes sense, since if infectious organisms were in their intestines they would already have the disease. The mere ingestion of small amounts of normal flora may be somewhat disgusting but is not a cause of disease, according to colleagues who are not only microbiologists, but infectious disease specialists. If you're saying that they contract it from their hiking companions who are already infected, I can make sense of that, but then again many of the people on this forum are mainly solo hikers.

But maybe I'm misunderstanding?

we just had a really long good thread on this

Here’s the recent thread that debunked many of Rockwell’s theories:
http://www.backpackinglight.com/cgi-bin/backpackinglight/forums/thread_display.html?forum_thread_id=68224

For example, the infectious dose is not 10 cysts as Rockwell claims. The EPA says “one or more.”

I don’t doubt you talked to Rangers who don’t treat water and claim they’ve never gotten sick. Without being tested, however, they wouldn’t know if they are now carriers of Giardia as about 2/3 of people are asymptomatic. Anecdotal evidence is risky too:

I know a Ranger who told me he got Giardia from the “Little Spring” on the Half Dome trail. Ranger Dick Ewert told me he has had it 3 times from the Yosemite water.
Park Rangers Getting Waterborne Giardiasis

So as to avoid going over old ground too many times, here’s links to a couple of posts I’ve made on the topic:
Debunking a Skeptical Giardiasis Paper
Waterborne Giardia: No Myth

Two quotes from those posts:
From a more recent survey in the high Sierra which included seemingly pristine water: “Nowhere is the water dirtier, he discovered, than on U.S. Forest Service land, including wilderness areas, where beef cattle and commercial pack stock — horses and mules — graze during the summer. There, bacterial contamination was easily high enough to sicken hikers with Giardia, E. coli and other diseases”…”Several backpackers appear weekly at Centinela Mammoth Hospital in Mammoth Lakes sick enough with giardiasis to need urgent care”

Both water treatment and hygiene are important.

"Without being tested, however, they wouldn't know if they are now carriers of Giardia as about 2/3 of people are asymptomatic."

What difference does it make if you're asymptomatic?

Not that I'm arguing with anyone and appreciate the threads, thanks

Wonderful post Buck!! I read your blog post from last year and it was perfect. I am a medical researcher and its nice to see some real data and study citations to debunk a rather unhealthy myth.

The reason it's important to note that 2/3rds of people infected are asymptomatic is because there is a rather large group of people out there trying to convince others that there is no need to treat water sources because so few people get sick. The point is that yes you absolutely might be infected but won't necessarily demonstrate symptoms.

So all those folks who say they've never gotten sick or that they don't know anyone who has gotten sick might, indeed, actually be sick…just not outwardly. So without a stool test there is no way to know if you ingested giardia (or any other bug…) or not, so people need to stop saying they didn't. Because there are those 1/3rd who, if they took that advice, would be very ill indeed.

But if you're one of the 2/3 that are asymptomatic, then maybe the strategy would be to not worry too much about treatment, until you become sick.

Then, you will know that you have to be careful about treating water.

"What difference does it make if you're asymptomatic?"

1. You can spread it to others via your hand to their food if you don't practice good hygiene, or by contaminating ground water if you don't pick good p00ping locations.

2. If your boddy gets stressed or run down, the infection good become acute.

Again, not being argumentative, just curious

1. but you could have E-coli or whatever so you should wash your hands regardless, doesn't matter if you also have Giardia. And you should bury the material so it doesn't get into water

2. That makes logical sense. And with poison oak, you can be insensitive, then get one case, and from then on be very sensitive. Maybe Giardia is the same? If you're careful to minimize exposure maybe you'll continue to be insensitive and never have a problem, but if you're not careful, you could get one bad case and from then on be super sensitive? That would be tough to get any data on to verify.

Brian,
I generally agree with your conclusion on water in the high Sierra, read in the National Parks away from horses and high concentration of campers. I don't treat water in those areas. But go beyond those areas and you will find a complete menace, cows and their sheet. You will find it just south of Sequoia, just north of Yosemite and in far too many places on the PCT. I personally believe that this is the single biggest factor in thru hikers getting giardiasis on the PCT. Coming in at a distance second would be hygiene though this isn't much of an issue for me single I rarely hike with anyone or share food. Bottom line, I think you are over simplifying the issue by limiting the discussion to the high Sierra.

Hi Brian,

I'd like to break down your arguments more specifically, because many people make similar ones.

"since a bowel movement may expose you to 100s or 1000s of cysts, whereas in general, drinking higher elev wilderness water sources may expose you to 0 or 1 or 2 cysts in a week or 3, which source is the real danger?"

Of course, hygiene-wise we can't get giardiasis from ourselves, only from hiking partners. In the wilderness, most of us are potentially exposing ourselves to the bad hygiene of very few people. In our normal lives, we are potentially exposing ourselves to the bad hygiene of thousands of other people. I think it's fair to say that communicable diseases are a greater threat in the cities than in the backcountry for that reason. As for untreated surface water, we are potentially exposing ourselves to the bad hygiene of all people and many wild animals who have been in or near the water source in the preceding weeks. Also, giardia cysts survive much better in water than in the air.

A week of wilderness water might expose a person to 0-3 cysts, but that might be enough to make someone sick. Some "pristine" backcountry water has been tested and found to contain 20 cysts per liter.

"2 facts: giardia's presence is such that if you drank 50 gallons/day you could never find a high enough concentration in the water. And, you are FAR more likely to contract giardia from a hospital or a daycare center in the US than high elevation wilderness."

Both those "facts" are wrong and so are extremely misleading. There is no way of knowing for sure how much untreated surface water it will take to make someone sick. Even an educated guess is just that, a guess. "a high enough concentration to make you sick" is potentially ONE viable cyst. (source, EPA)

The crowd we are speaking to here is backpackers. I respectfully disagree that I am more likely to get giardiasis from a day care center or a hospital than wilderness water. The reverse is definitely true for the typical small child.

The CDC specifically says that backpackers or campers who drink untreated water from lakes or rivers are among those at greatest risk of giardiasis.

Fecal matter is frequently found in backcountry water. With all due respect, your Bottom Line Two and Three statements are speculation presented as fact.

I followed the http://www.ultrunr.com/giardia.html link. It's another repeat of the Rockwell paper along with comments. As usual, there are people who agree with your point of view. Others are not convinced. Here are a few quotes:
The most sick I have ever been was after a backpack trip in the Emigrant Wilderness, north of Yosemite, and drank without treating water which I thought was not necessary in the Sierras. I tested positive for Giardia. I always treat my water now…

Well, I live in the Sierra Nevada up in Mammoth. I'm careful, almost always use a filter and I've still gotten Giardia three times…[note he said "almost always"]

[The following snips are all from one comment:] I am a Doctor (and a microbiologist). …I spent summers in northern Canada where it is endemic and have had giardiasis many times…I picked up Giardia in 1992 on a canoe trip in northern Saskatchewan…I drank from a stream in the 1998 Elkhorn Mountain 100 km (Montana) and got a pretty severe case.

Hardly as rare as shark attack, the analogy Rockwell and Welch have used.

I would like to see real data on infection with giardia, i.e. controlled studies.

There is controlled infectious study data on Cryptosporidium. Possibly because it has infected municipal water supplies sickening as many as 400,000 people at once before (Minneapolis).

Even at 1000 cyst dosage, only 77% of test subjects become infected. At 10 cysts, only 20% became infected. In all the cases only about 28% of the people who were infected actually developed the full blown sickness and began passing cysts.

I would expect giardia to be similar. Individuals immune systems have a significant impact on infection rates. Persons with compromised immune sytems, ie. HIV positive, etc can contract forms of crypto that normal people dont, such as those carried by housecats. I think theres about 20 forms, we are concerned with 1.

So can a person get sick from 1 cyst? Maybe. Is it likely? No. Are you likley to encounter many cysts by getting water out of a piped spring near the ridgeline of mountains? Nope.

Even with lots of peoplepoo that is buried, water percolating thru soil is rendered sterile in a very short distance. This is how septic tanks work.

The danger is from surface water, and runoff of areas where humans camp and livestock are.

Regardless, giardia isnt really a concern. ClO2 reduces it 1000 fold in just 6 minutes. Crypto is what takes too long to treat effectively, about 3.5 hrs for 1000x reduction.

"Some "pristine" backcountry water has been tested and found to contain 20 cysts per liter."

Could you give us some specific locations? I am particularly interested in the Sierra.

M B

Those are some good questions and observations. There has only been one study done to determine the infectious dose for giardia as far as I know. It was extremely limited.

Go to this link and scan down until you see the graph. Clearly the infectious dose is very low, lower than 10 cysts. I’ve found two different sources that estimated the odds of infection with one viable cyst: one said 1% and one said 2%.

Apparently some strains of Giardia are more infectious than others, and of course some people are much more susceptible than other people.

Tom, the 20 cyst per liters case I was thinking of was from a Wisconsin study, but there’s little doubt that similar concentrations are out there at certain places at certain times in every state.

"Tom, the 20 cyst per liters case I was thinking of was from a Wisconsin study, but there's little doubt that similar concentrations are out there at certain places at certain times in every state."

Buck – I don't doubt that every state has those concentrations in certain places, very likely in less remote locales for the most part, but my interest is in pristine places. No study that I am aware of has ever found that high a concentration in the Sierra, or even 1 cyst/liter. Since I spend quite a bit of time there and seldom treat my water, I am naturally very interested in knowing about Sierra locations where high concentrations of giardia have been detected. If you run across any information that so indicates, I would really appreciate your posting it here on BPL. There are a lot of us here who would thank you.

Tom

Tom

Here's a quote from a newspaper article about a fairly recent survey in the high Sierra which included seemingly pristine water: Nowhere is the water dirtier, he discovered, than on U.S. Forest Service land, including wilderness areas, where beef cattle and commercial pack stock — horses and mules — graze during the summer. There, bacterial contamination was easily high enough to sicken hikers with Giardia, E. coli and other diseases.

http://www.modbee.com/2010/05/08/1158938/fouled-waters-sierra-lakes-streams.html#

You said: No study that I am aware of has ever found that high a concentration in the Sierra, or even 1 cyst/liter.

I think Rockwell and Welch have done a huge disservice to backpackers for leading people to believe that it is reasonable to make a risk assessment based on average concentrations shown in old surveys. It's not. It's the concentration in the water we are about to drink that matters, and there's no way to determine that in the field. We can only make educated guesses, and myself and many others have guessed wrong. If the person ahead of me dips their canteen with dirty hands in a perfectly pristine Spring it is no longer pristine. The very old 1984 studies that are repeatedly quoted found Giardia in 1/3 of water sources. There is some risk from a single cyst.

The EPA says: "Cysts have been found all months of the year in surface waters from the Arctic to the tropics in even the most pristine of surface waters"
http://water.epa.gov/action/advisories/drinking/upload/2009_02_03_criteria_humanhealth_microbial_giardiaha.pdf

"there's a ton of people who don't wash their hands in the city after having a BM and you'd think they'd spread giardia then as well?"

Only if they have it in the first place.

"Here's a quote from a newspaper article about a fairly recent survey in the high Sierra which included seemingly pristine water: Nowhere is the water dirtier, he discovered, than on U.S. Forest Service land, including wilderness areas, where beef cattle and commercial pack stock — horses and mules — graze during the summer. There, bacterial contamination was easily high enough to sicken hikers with Giardia, E. coli and other diseases."

I think maybe we have different interpretations of the word "pristine", Buck. Any location where farm and pack animals are allowed to graze is hardly pristine. IMO, any person who drinks untreated water in such areas is just asking for trouble. Of course you treat water in such conditions! What I am interested in is information regarding giardia concentrations in truly pristine areas, typically off trail and far from the crowds that in creasingly frequent the JMT, Emigrant Basin, Mt Whitney Zone, etc.

"I think Rockwell and Welch have done a huge disservice to backpackers for leading people to believe that it is reasonable to make a risk assessment based on average concentrations shown in old surveys. It's not. It's the concentration in the water we are about to drink that matters, and there's no way to determine that in the field."

In the absence of hard data to support your claim that giardia lurks everywhere, I think you risk doing a similar disservice by spreading fear where there is little, if any, danger. The kind of places Rockwell frequents still do not see a lot of traffic. What is the vector for spreading giardia to such places, along with new supporting data that would invalidate the last concrete data we have? What he says agrees with my own personal experience over several decades of wandering around in such areas, as well as many here on BPL, if I am not mistaken. This is not to say there is no danger, but that it is small enough to allow a person to proceed on a site by site basin, using knowledge and judgment to determine whether or not to treat.

One of those old studies of Sierra water was unable to find concentrations greater than .12 cysts/liter, IIRC. If you want to check it out, read thru previous threads on the subject here on BPL, as I do not have the link at hand. I suspect you are already aware of it, in any case. Bottom line, from what I have read, the risk varies considerably by location. What applies in the Rockies, Cascades, Alaska, etc, is probably not relevant for the Sierra, and vice versa. Similarly, what is valid in the Sierra for high use areas, particularly where stock grazing is allowed or there are high concentrations of backcountry users, is not valid for remote, off trail areas. All that said, I will be most interested in any SPECIFIC information pertaining to such areas that you or anybody else can present. After all, it's my a$$ on the line, so to speak.

Edited to remove a comment on something I missed in a previous post.

Tom, you need to lead a field research team to Lake South America and sample the water there for about two or three months.

Incidentally, when I am in such remote areas, I think about the large mammals that might be traveling around to spread giardia cysts. Typically, you can't find any large mammals at all, but they are there. Bighorn sheep rams wander a lot.

–B.G.–

"Tom, you need to lead a field research team to Lake South America and sample the water there for about two or three months."

I've been sampling it anecdotally for many years. No problems so far. Guess I must be asymptomatic. ;)

"Incidentally, when I am in such remote areas, I think about the large mammals that might be traveling around to spread giardia cysts. Typically, you can't find any large mammals at all, but they are there. Bighorn sheep rams wander a lot."

I worry at least as much about the little critters. Voles, for instance, are a major vector in the Cascades. And I do treat the water up here. ALWAYS.

"I worry at least as much about the little critters. Voles, for instance, are a major vector in the Cascades."

It seems like it would take an awful lot of voles to get enough output to vival what one bighorn sheep ram could output. I wonder if some mammal species are asymptomatic as well.

–B.G.–

"It seems like it would take an awful lot of voles to get enough output to vival what one bighorn sheep ram could output."

True, but they're a lot more numerous and tend to hang around and in water, at least up in the Cascades. They're also found in the Sierra, but I have never seen one up high, which doesn't mean they're not there. All in all, it's a calculated risk. I'm willing to take that risk in many of the places I visit because there is something qualitatively very special about drinking the water without the barrier of treating the water coming between me and that beautiful environment. Hard to explain, but I suspect some of you will understand what I'm getting at.

Hi Tom,

Have you read through the information on the links I posted on this thread 10/12/2012 09:57:15 MDT? It covers much of what we are discussing.

Dr. Derlet is considerably more qualified to determine what sources are likely to be pristine than most of us. "What [Derlet] has learned, after analyzing hundreds of samples dipped from backcountry lakes and streams, is that parts of the high Sierra are not nearly as pristine as they look."

The EPA said "Hancock et al. (1997) collected 463 groundwater samples from 199 sites in 23 states in the United States; Giardia cysts were found in 14% of the springs."

The book Nols Soft Paths: Enjoying the Wilderness Without Harming It says "In a study of pristine streams in the Sierra Nevada, Forest Service Hydrologist Thomas Suk and his colleagues found that 35% of the water tested had dormant giardia cysts."

You said "In the absence of hard data to support your claim that giardia lurks everywhere, I think you risk doing a similar disservice by spreading fear where there is little, if any, danger." Remember the EPA says "Cysts have been found all months of the year in surface waters from the Arctic to the tropics in even the most pristine of surface waters." They aren't saying all waters all the time, and I'm not either. There's plenty of hard data showing cysts are often found in places people would believe to be pristine, including the Sierra.

People are welcome to treat water or not. It's their choice. We all know people that have gotten by for years without treating and without getting seriously sick. Most of us with many years of backpacking also know people who have gotten giardiasis after not treating their water. My cited studies showed many people get giardiasis on a single trip. Pointing that out isn't paranoia, it's reality.

Rockwell said "you can indeed contract giardiasis on visits to the high mountains of the Sierra Nevada, but it almost certainly won't be from the water." I believed him and got giardiasis after following his advice on my first long hike in the Sierra. He paper is fraught with misinformation of many kinds and his conclusion isn't supported by good science.

Here is the Derlet paper, for those who would like to examine it first-hand:
http://www.ericjlee.com/Articles/Sierra%20Water%205years.pdf

"In wilderness areas where cattle or pack animals have been present, we recommend that drinking water be treated. In Sierra Nevada wilderness areas, water from alpine sidestreams that are free from upstream domesticated animal use have a very low risk of harboring coliforms and we believe have a minimal risk of illness if drunk untreated."

After seeing his data, I will be much more cautious around areas frequented by pack animals. I will continue to occasionally drink water untreated from truly wild areas as a calculated risk, since it is so darn delicious.

Andrew