Giardia Cysts and Giardiasis
(say "gee-ar-dye-a-sis")
Waterborne Disease


Mr. Brian Oram, PG
B.F. Environmental Consultants Inc.

Giardia Cysts and Giardiasis (say "gee-ar-dye-a-sis")

giardia cysts, oocysts, trophozoites

Water Treatment Systems
Water Testing Kits

Recent changes in the EPA Drinking Water regulations and the development of the SOURCE Water Protection strategies have required water suppliers using springs or groundwater sources to evaluate drinking water sources for the presence of trophozoite).

The cyst stage is the stage the is responsible for the spread of the organism. Giardia (say "gee-ar-dee-ah") cysts are elliptically shaped and range in size from 6 to 10 microns. The cyst stage could be thought of as the equivalent of a "seed" or "spore", the structure of the cyst makes the organism very resistant to environmental factors and disinfection. The cyst stage is the "life stage" that will be found in the environment.

After entering the host, the stomach acids causes a reaction that causes the cyst to excyst, i.e., "hatch like and egg." The cyst does not hatch in the stomach, but in the intestine. The organism quickly subdivide and attach to the lining of the intestine. This is the second life stage - the trophozoite. The trophozoite stage, Giardia duodenalis - species that infects humans, is approximately 12 - 15 microns by 6 - 8 microns. The organism has a pointed elongated median body. The trophozoites contain four pairs of flagella.

What are the Health Effects analysis ?

After viable oocysts are ingested, there is an incubation period of 2 to 12 days. Typically the average incubation period is 7 days. The primary symptoms include: diarrhea, abdominal cramps, headaches, nausea, vomiting, and low-grade fever, which can lead to weight loss and dehydration. For the average human being in good health, the symptoms last approximately two weeks, but for immunocomprimised individuals, the disease can last for months and can be fatal. The individuals most at risk to this disease, if exposed, includes: AIDS patients, organ transplant recipients, malnourished children and individuals receiving certain cancer treatment . 

Note: There are some people that have Giardia in their system, but do not get ill.  These individuals are asymmptomatic and could act as carriers or host and spread the disease or infect the other members of the household or family.  This why all members of the household should be tested.

Treatment Options

In adults, giardiasis is commonly treated with a drug called metronidazole (otherwise known as Flagyl). Usually the drug is taken 3 times a day for 5 to 10 days.  For children less than 5 years old, the treatment is typically with a drug known as furazolidone (or Furoxone).  Typically the drugs have side effects similar to the disease.

Detection of Giardia in Drinking Water

The procedure used for Giardia is known as the immunofluorescent antibody method. The procedure requires that a minimum of 100 to 1000 gallons of water is filtered through a 1 micron filter. The filter is then cleaned and the material collected and centrifuged. The centrifuged pellet is then floated using a Percoll - Sucrose density gradient technique. The floated material is then cleaned and centrifuge and the pellet is then stained with a fluorescent antibody. 

immunofluorescence, giardia cysts, giardiasis, oocyst, fluorescene
Source: EPA Website

Slides of the pellet are prepared and the slides are examined for the cysts. If a cyst is suspected, the slide is then examined using Hoffman Modulation to confirm the proper shape, size, and at a minimum two internal structures. If you need a well, spring, or filtration plant evaluation the Center for Environmental Quality can assist you organization, business or local municipality.  For More information on Giardia MPA MET Testing, please contact Giardia Analysis.

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Great Books on Giardia

New Approaches for Isolation of Cryptosporidium and Giardia

Evaluation of Antibodies to Cryptosporidium and 
Giardia Using Flow Cytometry

Giardia and Giardiasis: Biology, Pathogenesis, and Epidemiology (This is a Great Reference !)

Water Treatment Systems

Whole House Treatment System for Giardia, plus a
Sediment Filter Fitted with a 0.2 micron Filter

UV Disinfection Systems (6 to 12 gpm) and
other water treatment systems
In-line Ozonation System

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