Giardia: Top Symptoms You Need To Know


Giardia lamblia (aka Giardia duodenalis, and Giardia intestinalis) is yet another protozoan parasite frequently encountered here in the Byron Bay region. Where you find other protozoan parasites, Blastocystis hominis, Dientamoeba fragilis and the likes, giardia should be on the radar as well.

Giardias incidence Australia wide is unclear. Many warm temperate and sub + tropical areas of Australia are the perfect breeding ground for the bug and many rural Australian’s use rainwater, a potential contamination vector, as their primary water source

Giardia is a very common gut infection inhabiting an estimated 13% of adults and up to 50% of children. The CDC puts giardiasis at the top of detected intestinal parasites in the USA (3).

“Giardia lamblia, the causative agent of human giardiasis, is endemic throughout the world; in Asia, Africa and Latin America, about 200 million people have symptomatic giardiasis, with some 500,000 new cases reported each year [1]. In fact, it has been estimated that the population at risk of giardiasis all over the world is more than one billion” (4).

Giardia – Life Inside the GI Tract

As an obligate parasite, Giardia needs a host to complete its lifecycle. Like many protozoans it has at least two stages in it’s lifecycle. The first stage, the nonmotile cyst stage, enables giardia to live outside of it’s target host’s intestinal tract. This cyst stage, seen in the image below, is the part of the lifecycle that is responsible for infection.


Once ingested the cyst makes its way to the host’s small intestine. It then undergoes excystation and morphs into a motile trophozoite. This is the stage that is responsible for the symptoms related to giardia infection. The parasites can then replicate and suction onto areas within the small intestine, causing the symptoms that you might be experiencing now.

The lifecycle is complete when encystation occurs. Triggered by digestive bile salts and an alkaline PH the trophozoites form cysts and are then excreted by the host. In this stage they can can survive for months in a suitable environment (5).


Consequences of Giardia Infection

Many people can harbour Giardia and not display overt symptoms. The question remains as to whether asymptomatic patients are still suffering poor health or not. Moises Velasquez-Manoff argues quite strongly that a background parasitic load was a constant presence in our evolutionary ancestry. In his book An Epidemic of Absence he outlines how many common parasites have helped shape our immune system and in their absence our immune system can suffer.

Giardia has been shown to colonise a host without symptoms and there have been suggestions that it can protect against diarrheal disease (5).

That said, the cases of serious health issues involving Giardia infection are many.

“While Giardia lamblia is known to produce gastrointestinal distress including diarrhea, weight loss, flatulence, cramps, belching, distention, anorexia, vomiting, fatigue, mucus in the stool, bloody stool, and/or foul smelling stool, to name a few, it must be borne in mind that the parasite can produce a continuum of pathologies ranging from no symptoms to extremes of illness requiring hospitalisation. A complete understanding of how pathogenesis is produced is not available; however, it is known that the strain of parasite, along with the immune competency and health status of the host, are important factors.” (3).

Top Symptoms Of Giardia Infection

  1. Diarrhoea
  2. Weight loss and
  3. Abdominal cramps
  4. Malabsorption symptoms (nutrient deficiencies)
  5. Failure to thrive in children
  6. Nausea
  7. Vomiting
  8. Flatulence
  9. Fever
  10. Anorexia

It’s interesting to think that all of these unpleasant symptoms can be caused by the microscopic unicellular creature in the image below!


Giardia Infection – Specific Issues

  • Small intestinal malabsorption
  • Temporary lactase deficiency (leading to lactose intolerance)
  • Vitamin A deficiency
  • Vitamin B12 deficiency
  • Folate deficiency (4).
  • Failure to thrive in children
  • Nutrient deficiencies
  • Rapid weight loss

Avoiding Giardia Infection – Transmission Routes

The first thing would be a simple understanding of the Giardia life cycle and common routes of infection.

Surface water is at the top of the list, and contamination is dependant on the level of faecal pollution and human use. Unfortunately, due to their robust nature, the giardia cysts are quite hardy and resistant to disinfectants used in water treatment.

‘Filtration of such waters is essential to the production of safe drinking-water: treatment by disinfection alone offers…only limited protection against Giardia.’ (3).

Proper filtration of surface water is essential in avoiding possible giardia infection! I have written before on the importance of water filtration for anyone living on tank water. This is a common scenario for many people living in the Byron Bay hinterlands, and most of rural Australians as well. Making the connection that tank water is surface water is important.

giardia routes of infection natural treatment australia naturopath

Image taken from: Review article: the management of Giardiasis

What to do if you suspect infection

If you or someone you know suspects that they may in fact be infected with giardia the most important thing to do is to test.

Here in Australia many doctors are recommending the polymerase chain reaction test (PCR) to screen for the top infections. Thankfully giardia makes the cut and can easily be screened for with this test. Medicare covers the cost, so it is free. Just make sure that the PCR test is being ordered and not the old fashioned culture and microscopy test. These are outdated and tend to miss more infections than they find.

The best test to assess for Giardia is a stool tests called a PCR – polymerase chain reaction – test.

To delve deeper here are a few articles on the subject of stool testing.

The results obtained from a functional stool test are incredibly informative. Personally it was the best thing that I did to get my health back on track. Based on the results from these comprehensive stool tests, personalised health plans can be formed by any number of trained functional medicine practitioners or herbalists.

Natural Treatment Options For Giardia

Natural parasite treatments is a topic that has been covered here many times before. I am very passionate about helping people treat their gut infections without causing issues later on down the track. I have concerns with the overuse of antibiotics, including the rise of antibiotic resistant bugs (Clostridium difficile is just the beginning in my opinion) to the long term negative impacts it can have on our resident gut flora. The same can be said for many of our strong herbal antimicrobials. Caution is advised.

Thankfully giardia is quite susceptible to many of our herbal antimicrobials including garlic (11),  oregano, and guava leaf (12). Many other herbal antimicrobials are helpful, and in most cases natural treatment for Giardia can be effective in as little as two weeks of herbal treatment.

guava leaf natural treatment for giardia infections byron bay australian naturopath gut health specialist

References and Resources

  1. Blastocystis hominis – a protozoan gut parasite
  2. Dientamoeba fragilis -a most unusual protozoan parasite
  3. AWWA manual 48
  4. Management of chronic Giardia infection.
  5. A systematic review and meta-analysis of the association between Giardia lamblia and endemic pediatric diarrhea in developing countries.
  6. An Epidemic of Absence: A New Way of Understanding Allergies and Autoimmune Diseases
  7. Byron Bay – Is That a Parasite I Spot?
  8. Recommended GI testing – CDSA + PCR
  9. Stool Testing – My Personal GI Results CDSA + PCR
  10. Review article: the management of Giardiasis
  11. The microaerophilic flagellate Giardia intestinalis: Allium sativum (garlic) is an effective antigiardial.
  12. In vitro effect against Giardia of 14 plant extracts

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