Viewing Giardia Protozoa better through 3D modelling
by Mol Smith 2010
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Giardia lamblia - an outline
Giardia was first discovered by Antony van Leeuwenhoek in 1681 when examining diarrhoeal stools from himself. Although it was not really identified as a cause for serious infection until quite recently. Debate still continues regarding this parasite. It is a binucleate flagellated protozoan which can alternate in its life-cycle between an active motile (swimming) trophozoite and a resistant cyst which is infectious. It is possible to see this parasite in stained sections of the upper portion of the small intestine of infected people and animals. Leeuwenhoek must have been severely ill, I surmise, because it is quite difficult to find this parasite in stools due to the fact they have 'sucking discs, 'enabling them to cling on tightly to the intestinal mucosa! This is when they are in their swimming trophozoite part of their life-cycle. It is thought they feed on mucous secretions, reproducing in large numbers to form dense problematic populations, which then interfere with nutrient absorption by the intestinal epithelium.

Infection and disease
lamblia is responsible for around 30,000 people yearly suffering waterborne disease causing diarrhea. The protozoan probably causes 200 million infections world-wide per year! Infection is affected by encysted Giardia being excreted by humans and animals and ending up in 'clean' water supplies. Many people in the states, exploring the natural environment of remote areas, become infected by drinking from what appears to them as crystal-clear freshwater. The resultant illness has been coined as 'Beaver Fever' since it is known that the animal is probably the cause of the encysted Giardia being deposited directly into the water with its faeces, although deer, sheep, and rodents contribute too.

The Giardia cysts survive for months in cold water and may be present in any water system especially naturally occurring ponds, storm water storage systems, as well as clean-looking mountain streams. As they are resistant to traditional water treatments such as chlorination and ozonolysis, they may also occur in city reservoirs. Problems with infection may also also occur in baby or child-care day centres through direct or indirect contact with contaminated child faeces if hygiene practice control is poor.

Viewing Giardia with a light microscope
The protozoa can be seen with high magnifications under a light microscope, although they more often appear as elongated crescents such as in this stained section below Fig.1 (please see copyright information on resources page). I have marked an area here with a dotted line so you can see a cluster protozoa.

Fig. 1

A scanning electron microscope can provide us with a much better view of this entity so that we can understand more about its ability to 'cling' to the wall of the intestinal lumen. So let's
take a closer look here...


Comments to the author
Mol Smith are welcomed.

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Published in Feb 2010 Micscape Magazine.
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