The Giardia ‘Syndrome’ Strikes: Norwegian Studies Suggest ‘Minor Bugs’ May Commonly Trigger Chronic Fatigue Syndrome As Well

November 29, 2012

by Cort Johnson

“Other patients suffer a severe, long lasting illness, for which treatment is ineffectual, and even after the parasite has finally been eliminated, some sequelae persist, affecting quality of life and continuing to cause the patient discomfort or pain” (LJ Robertson et al, 2010)

Giardia is an interesting bug. Perhaps the most common intestinal parasite in developing areas, it’s not generally considered much of a threat in the developing world, but with a lowball figure of 20,000 cases the US in 2010 some researchers think of Giardia as a ‘re-emerging’ infectious disease.

Giardia, though, is not normally considered a serious infection. Most people pass the bug quickly – and if they don’t, effective antibiotic treatment is available; ie it’s an ‘uncomplicated infection’ that the medical system believes it has largely taken care of and thus spends its energy on the big bugs like HIV.

Uncomplicated Infection?

An ongoing series of Norwegian ME/CFS studies suggest that the medical community should think again. They indicate that a Giardia infection, like many other pathogens that largely fly under the medical research system’s radar, can be anything but uncomplicated. Let’s take a look at what the three Norwegian Giardia studies found resulted from one outbreak in Bergen, Norway.

Anything But Uncomplicated

Their data suggests that Giardia infections can pose significant long term health risks. Three years after being exposed to a Giardia infection of their water supplies, almost 50% of those originally infected still had symptoms of irritable bowel syndrome and/or chronic fatigue.

Overall, being exposed to Giardia doubled their chances of experiencing significant fatigue, with five percent suffering from fatigue severe enough for them to lose employment or to be unable to continue their education.

All had taken anti-parasitic drugs and tests indicated that all had cleared the pathogen from their systems….but three years later they were still ill.

What Had Happened?

Until more complete analyses are done it’s hard to tell why and nobody knows…and unless more studies are done nobody will know. Several answers have been suggested…

  • The Sneaky Pathogen theory – Low levels of the pathogen – as yet undetectable – are still present and producing a low grade inflammation that is causing fatigue, abdominal distress and other symptoms.
  • The Hit and Run Theory – The pathogen damaged their intestinal surfaces causing permeability issues, hypersensitivity, bacterial overgrowth, immune reactions and irritable bowel syndrome.
  • The Other Immune System Problem – The Giardia attack triggered mast cell activation in the gut. Mast cell activation appears to be occurring in fibromyalgia and has been associated with fatigue, depression and psychological changes in irritable bowel syndrome.

Not Depression – The Norwegian studies indicated that depression and anxiety prior to becoming ill did not play a role.

CFS-Like Group – In the Bergen outbreak, questionnaires revealed – similar to ME/CFS – that the patients’ physical functioning and vitality were hit the hardest. Higher rates of questionnaire-assessed anxiety and depression appeared to either be a feature of the illness itself and/or the result of having a chronic, poorly treated illness – not ‘primary’ depression.

Variable Appearance – While the infection was ‘acute’ (i.e. it happened suddenly), the time to distress varied dramatically. About 30% experienced debilitating fatigue immediately, but the months it took for approximately 60% of those infected to get really whacked with fatigue suggested that very different disease courses could occur in response to the same infection. Some studies do suggest that these allied disorders tend to merge together over time – that is, people with CFS tend to pick up IBS and IBS patients tend to meet the criteria for CFS as they ‘mature into their illness’. ( :) ). Fatigue did not always occur at an early stage in the early myalgic encephalomyelitis outbreaks. It’s possible that it simply took time for that symptom to ‘flourish’.

Anyone who’s gone backpacking and camping in the US and didn’t filter their water could have been exposed to Giardia. I was exposed on a backpacking trip several years before I came down with chronic fatigue syndrome and later tests suggested it was still present. I also have IBS type symptoms – did Giardia contribute to my illness? I wouldn’t be surprised at all, given all my abdominal complaints…
There are lots of options and, as we hear so often with ME/CFS, these authors believe that a number of little things go wrong in post-infectious giardia to create a big, bad thing:

“Thus, there is good reason to believe that predisposition for persistent giardiasis is based not on a single mechanism or deficiency, but rather on a combination of several minor deficiencies of varying degrees in each individual’s anti-Giardia defences.”

Immune System

Tests revealed an activated immune system with increased numbers of cytotoxic (i.e. killer) T-cells on the prowl for invaders – a pattern also found in people with infectious mononucleosis, herpesvirus infections such as cytomegalovirus and herpes simplex, dengue fever, etc. That response, however, was more often found in people diagnosed with what the authors called post-giardiasis functional gastrointestinal disorders (people with IBS-like problems after a Giardia infection) than in people later diagnosed with ME/CFS. (Note that the Fukuda criteria was used to diagnose CFS…..).

Reduced NK cell functionality has been documented in ME/CFS, but studies of NK cell levels have had variable results. Several studies, including this one, found reduced NK cell levels in post-infectious patients, suggesting that both NK cell levels and functionality could be impaired in patients with infectious onset. This suggests that the NK cell level test could demarcate patients who got whacked with a bug (eg post-infectious patients) from those patients with other types of onset.

The Role of Infection (Any Infection?)

Infection is not just a trigger for chronic fatigue syndrome. Infections can also trigger fibromyalgia and irritable bowel syndrome. In fact, a recent meta-analysis indicated that having an acute attack of gastroenteritis – the stomach flu – results in a six-fold increase in one’s risk of coming down with IBS a year later.

With a significant number of IBS patients also meeting the criteria for ME/CFS, it’s clear that other infectious gastrointestinal pathogens trigger ‘ME/CFS’ as well and it’s probably only a matter of time before they’re added to the list. Ultimately people with severe fatigue and bad gut problems probably get diagnosed with ME/CFS or IBS depending on which doctors they see first.

Invisible Infections Wreaking Havoc?

Our medical system is good at hacking away at the big bugs – the HIVs, the Plasmodiums (malaria), the cholera and the West Nile Viruses – that leave obvious amounts of death and destruction in their wake, but it is very poor at examining the effects of bugs whose cost is not so immediate or obvious.

Enteroviruses are often also considered uncomplicated infections that sweep through a community, knock people out for a couple of days and then move on, but Dr Chia’s findings suggest these infections can be life-changers for some. Long term follow-up studies of even common infectious events such as infectious mononucleosis, for instance, are rare outside of the CFS field.

ME/CFS researchers may be underfunded but they have been pioneering follow-up studies examining the insidious and long term effects that infections like Giardia, Epstein-Barr virus, SARS (sudden acute respiratory syndrome), parvovirus and coxsackie virus can have. As these studies get published – there have been two in the last year or so – hopefully the medical community will take a closer look at the mysterious effects that pathogens, some largely thought to be mere nuisances, can have – even after they’ve apparently been cleared from the body.

In the next year or so, major pathogen studies from the Chronic Fatigue Initiative (Lipkin and Hornig), the CFIDS Association of America, the CDC and probably the Whittemore Peterson Institute should be published. A Montoya study also appears to be under way and Dr. Mikovits recently reported that she and Dr. Ruscetti are continuing to look for bugs as well. The CFI study will be the most complete and rigorous and may, if reports are correct, finish up in the next couple of months.

Positive results in these studies would support the ‘sneaky pathogen’ theory; negative results would support the ‘hit and run’ theory. Probably we’ll get a mixture of both…


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{ 15 comments… read them below or add one }

HowToEscape? November 29, 2012 at 12:30 pm

There were comments before, but now it shows 0.


alex3619 November 29, 2012 at 1:13 pm

This article was reposted and my comment was lost, but I was kindly informed about this so here it is again:

A sneaky pathogen offers a single target for treatment. I hope its right. However I think hit and run is more likely at this point. I also think we need to think of two separate things, something that was pointed out to me by a doctor in 1993. The first is what triggers the illness, the second is what sustains the illness. They do not have to be the same thing. I think many pathogens can trigger these issues. The question is what common immune pathway allows secondary consequences to persist? My current focus is on gamma delta T cells, and I hope to blog on that next year.

With respect to mast cell activation, gamma delta T cells are supposed to suppress that. If they are not working then even normal mast cells could be a problem.


Cort November 30, 2012 at 2:04 pm

I would tend more to hit and run as well for myself. I imagine the CFI study will show a group of patients with an active infection- enough people have done well on Valtrex/Valcyte to suggest that….but with FM and other disorders like IBS triggered by all sorts of infections (and other stressors) I think something gets jumbled up, turned on, turn around, damaged or reset or whatever during some infection/stressor and it pretty much stays that way.

Gamma delta T cells…hmmm – never heard of them; looking forward to that blog :)


Justin Reilly November 30, 2012 at 3:46 pm

Yes, looking forward to that blog too. Do you have a blog now Alex? I hope so bc I want to read any blog you write!

Cort thanks, this was interesting.

They are kind of cute. I kinda want one. I need a pet. ; )

Sing November 29, 2012 at 4:33 pm

Without being able to comment on the scientific analysis, I can add my own experience. I had a severe infection with Giardia when age 27 when I considered myself well. Giardia seemed well on its way to killing me after two months because I was bedridden, nauseated, very fatigued, could barely eat anything and had severe pain if I ingested certain foods like bran. I lucked upon an article about gluten-intolerance and Celiac Disease. Seeing the similarity in my digestive symptoms, I concluded that my illness must be attacking the small intestine (Make note: Giardia knocks down only the small intestine.) With this insight, a doctor was able to diagnose and treat Giardia, which at that time was barely known about and/or considered a minor infection which resolved on its own. Twice more in the next several years (still camping) I got Giardia. Each time I was the only human being in the group to get sick and it was from as small an exposure as a rinsed cup or toothbrush in stream water. These times I could immediately identify the characteristic symptoms and get the right antibiotic, Flagyll. I thought I had recovered completely, but with each later physical stressor in life, I have gradually accumulated the full complement of symptoms for ME/CFS–actually, ME, but with a gradual onset. In my opinion, Giardia was not the absolute first cause, however, but rather I was either genetically predisposed or my system had already been weakened and changed by something else, such that parasites and illnesses and stressors which a normal system could handle and rebound from were nailing me, one after the other, to the floor.

So, perhaps those who in this Norwegian study, went on to develop the symptoms of ME/CFS, already had its blueprint or tendency on board, and for this reason were particularly susceptible to Giardia, which then exposed their underlying weakness (immune deficiency or aberration).


Cort November 30, 2012 at 2:06 pm

That sure makes sense to me Sing..and that’s a pattern – getting hit by one infection…then knocked a bit down more by the next etc. that I think is fairly common…

I didn’t put it in the blog because I wasn’t sure but I do remember hearing there was a water borne infection and I think it was Giardia about the time of the Incline Village outbreak so long ago.


Sing November 30, 2012 at 3:07 pm

Cort, or anyone, is it thought that the, or a, water borne illness at Incline Village might have been Giardia? When I first got Giardia in 1975, doctors barely seemed to know about it and testing for it was very poor quality too. It was hard to see or find, being such an extremely small protozoan. And the effective drug was considered dangerous, so doctors didn’t want to use it unless you were tested positive. The standard belief is still that it is a minor illness, passed off by most people, but this was not true for me. It was severe and I doubt if I would ever have gotten over it on my own. Others here might chime in about illnesses you got in Third World countries or situations, and how your experience compared with fellow travellers. I always got sick in those circumstance, even if no one else did, and I got very sick. People like me–us–would do very badly in a war or survival situation. We would be among the first ones “out of here”.

HowToEscape? November 29, 2012 at 8:21 pm


Your observations sound like they would be useful. Most people with this stuff can do not have a single cause we can show is likely to be the central driver, just intuition. Your multiple exposures to the same agent comprise a history of immune centered dysfunction. We all “know” it’s the immune system, but without evidence that doesn’t get us far.

Perhaps we should start a database (anonymized, much mischief could be done with personal data) including
1. Cases where there is a fairly clear cause and effect, such as one I know of from occupational chemical exposure and cases like yours where the effects were linked in time and with plausible connection to a specific event.
2. Less clear cases, for people who want to post their histories. I can’t say what researchers would find useful, and some people may just want to post their experience.


BobM November 29, 2012 at 9:20 pm

Great piece Cort. I look forward to the results of those major pathogen studies. Lets hope they produce some results that can benefit our patient community.


Cort November 30, 2012 at 2:08 pm

Well, one way or another – they’re going to tell us something…..My guess is a subset with active infections and then there’s the rest of us….My big question is how definitive they will be…They will certainly be the most comprehensive tests yet….Will they be pretty much definitive? It’ll be interesting to find out.


Justin Reilly November 30, 2012 at 3:52 pm

Well, they seem likely to give some strong leads on pathogens, which would obviously be incredibly helpful and so I am REALLY excited about them. Oh boy, ACTUAL MEANINGFUL SCIENCE on ME! (that’s my layperson’s guesstimate anyway, fwiw)

Enid November 30, 2012 at 2:11 am

Great article again Cort – bits of the jigsaw puzzle (understanding) coming along.

(those enteroviruses look a happy lot – wish I could say the same for me – your graphics are a joy)


BobM December 2, 2012 at 7:03 pm

Call to Action for First Drug For ME/CFS: the Ampligen FDA Advisory Hearing

URGENT: ME/CFS Patient “A C T I ON” (A Call To Impact Our (me/cfs) Nation)

For All ME/CFS Patients,Families and Friends (U.S. & Non U.S.)

Organizer: Robert Miller and TEAM

For the first time people with chronic fatigue syndrome have the opportunity to make a difference in getting a drug approved for their disorder. At a public hearing on Dec. 20th an FDA advisory committee will advise whether Ampligen should become the first approved drug for chronic fatigue syndrome. As a part of that process they will review all comments produced by the ME/CFS community that are received by Dec 6th.
Ampligen presents a huge opportunity for the ME/CFS community. Not only has it been in the FDA pipeline for over two decades, it’s been the only drug under review for ME/CFS during that time. There are no other drugs waiting in the wings, no other drug companies developing drugs for this disorder; this is the culmination of decades of hope and the opportunity is large.

History has taught us that once a drug gets approved for a disease, other drugs, legitimacy and research dollars follow.
Let’s make history and get the first drug for ME/CFS approved in its long history by taking “A C T I ON” (A Call To Impact Our (me/cfs) Nation) and letting the FDA Advisory Committee know the urgency you feel for FDA approved drug treatments for this disorder.
Please send in your email by December 6th, and let the Committee know what it is like to live with ME/CFS daily and how needed treatment options are.

Our Advocacy Community will update you when other significant meetings are coming up, including the FDA Stakeholder meeting in the spring and issues dealing with CDC and NIH but right now we need the Advisory Committee hear from Our Patient Community on this issue.

This drug is our AZT to the ME/CFS community. If approved we believe it will be just the beginning of treatments to come.

A Sample Email Template is below

Send To:
Email address:
Subject line: Treatment for Chronic Fatigue Syndrome – Ampligen

To The Advisory Committee Reviewing Ampligen:

My name is ___________________ I have had CFS for more than ___ years. Before I became ill I had a life that was ______________________. My life since having CFS has been____________________________ . We need treatment. We deserve treatment and the ability to access it. Just like AZT for AIDS or Tysabri for MS or Benlystra for Lupus. We are not second class patients. According to CDC studies, CFS is comparable to MS, late-stage AIDS, Lupus, rheumatoid arthritis, heart disease, end-stage renal disease, COPD and the effects of Chemotherapy. CFS/ME effects every moment of my life. We have seen and heard of patients doing well on Ampligen. Give this community Hope by approving Ampligen. We want our lives back.

Thank you,
Full Name
Address Here
(Please Cc: emails to Robert Miller at:


BobM December 3, 2012 at 12:15 am

Please Note email Cc cntacts are incorrect, My Bad… the bobmiller gmail contact is

Thank you,

Bob Miller


annacermakova December 7, 2013 at 7:35 pm

Better understending what did happend after you got giardia

Way to get better:

Stimulate intestinal rejuvenation by providing healing nutrients
•A number of nutrients have been shown to repair damaged intestinal lining, and regulate the integrity of tight junctions: •L-glutamine – long known to be the primary amino acid source for intestinal cells, glutamine has recently been shown to regulate intercellular junction integrity.33
•N-acetyl glucosamine (NAG) – given the breakdown of glycosaminoglycans that occurs with leaky gut, this nutrient34 provides a substrate for repair of these tissues. A trial in children with IBD showed significant potential for this nutrient.
•Zinc – zinc deficiency has been shown to disrupt tight junctions, alter membrane permeability, impair immune function, and cause intestinal ulceration.35
•Antioxidants (such as vitamin C, vitamin E, beta-carotene, grape seed extract, and milk thistle extract) – not only protect the GI from oxidant damage, but also help with hepatic detoxification of compounds associated with intestinal dyfunction.
•Quercetin – this antioxidant appears to be critical to intestinal integrity, and acts through a number of mechanisms. These have been shown to include the assembly of a number of tight junction proteins (zonula occludens (ZO)-2, occludin, claudin-1, and claudin-4).36,37 Quercetin has also long been known to stabilize mast cells, which are important regulators of intestinal function and tight junction integrity.38
•Highly digestible, low-allergy protein, and water soluble fiber – nutrients known to restore intestinal health, while eliminating sources of damage. In addition to containing many important daily vitamins and minerals, RestorX™ contains the nutrients shown to have specific benefits in restoring intestinal integrity.

Good luck


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