Giardiasis Infection

Giardiasis is a diarrheal illness caused by Giardia intestinalis (also known as Giardia lamblia), a one-celled, microscopic protozoan parasite that lives in the intestine of people and animals.  Giardia has become recognized as one of the most common causes of waterborne disease (both through drinking water and through recreational use of water) in humans in both developing and industrialized countries. The giardia parasite lives in the intestine of infected humans or animals and is passed in stools.  The dormant form - a 'cyst' - is protected by an outer shell, making it exceptionally hardy and able to tolerate extremes of both pH and temperature.  It can survive outside the body and in the environment for long periods of time.  Giardia may be found in soil, food, water, or surfaces that have been contaminated with the feces from infected humans or animals.

Causes and Development

Early human research demonstrated that ingestion of fewer than 10 cysts failed to cause infection, whereas more than 100 cysts resulted in infection.

Once ingested, these cysts pass into the stomach, where they are exposed to gastric acid.  The low pH in the stomach and pancreatic proteases found in the proximal small intestine promote rapid breakdown of the cysts' outer walls within minutes of reaching the duodenum.  Typically, each cyst gives rise to two 'trophozoites', which are the vegetative form of giardia; they are able to colonize and rapidly replicate in the gastrointestinal tract as well as cause gastrointestinal symptoms.

Signs and Symptoms

Symptoms generally begin within 1 to 2 weeks of infection and include watery diarrhea, vomiting, stomach cramps, upset stomach, loss of appetite, dehydration, nausea and fatigue.  Less common symptoms include low-grade fever, chills, headaches, urticaria, and polyarthritis.  Mucous- and blood-tinged feces are rarely found.  Signs include weight loss, abdominal distension and tenderness, bad-smelling flatulence and burps, pale watery stools, frothy, foul-smelling stools.  Symptoms usually persists from 2 to 6 weeks in otherwise healthy individuals.

Symptoms range in severity from mild to extreme; however, a significant proportion of infected individuals are completely asymptomatic.  In some individuals giardiasis is short-lasting and resolves spontaneously, whereas in others infection can be prolonged and debilitating.

Diagnosis and Tests

Giardiasis is diagnosed by signs and symptoms, as well as the presence of giardia cysts and trophozoites in the stool.  Stool examination can be unreliable, however, as organisms may be excreted at irregular intervals, which can produce a false negative test result.  Hence, definitive diagnosis may require repeated stool examinations, fecal immunoassays, or even sampling of the upper intestinal contents.  Two stool examinations will detect 80-90% of infections, while three samples will detect over 90%.

Giardiasis can often be distinguished from viral or bacterial gastrointestinal (GI) infections by the longer duration of illness (often 7-10 days by the time of first presentation) and weight loss.  In addition, careful history taking may uncover recent travel to tropical or sub-tropical environments, wilderness exposure, or situations involving pool fecal-oral hygiene.

Treatment and Prevention

The most beneficial way to treat giardiasis naturally may be through a combination approach, utilizing both nutritional interventions and other natural agents.  Numerous medicinal herbs show promise in the treatment of giardiasis.  Blending nutritional interventions and phytotherapeutic agents can minimize giardia symptoms and aid in clearing the parasite, without significant ill effects.  As such, this therapeutic strategy is considered by many natural doctors as being the first-line approach.

The main aims of dietary modification in giardiasis should be to reduce the acute symptomatology, promote host defense mechanisms, and inhibit growth and replication of giardia trophozoites.  These aims can be achieved by consuming a whole-food, high-fiber, low simple-carbohydrate, low-fat diet.

This diet will ensure adequate amounts of lignins and insoluble and soluble fibers are consumed, which can increase mucin production in the small bowel, sequester bile acids, and help to mechanically sweep trophozoites out of the small intestine.  Consuming foods low in simple carbohydrates limits the amount of sugars available in the intestinal lumen, which may lessen the osmotic draw of water into the intestinal lumen, and reduce diarrhea.