in vitro culture and isoenzyme analysis of giardia lamblia

Figure 1.3. Transmission Electron micrograph of the small intestine in murine
giardiasis (right) compared to the normal jejunum of an uninfected control animal
(left) (Roberts-Thompson, et al., 1976). (x 160) (Courtesy of A.Mahmoud)
Smith et al., (1982) tested four strains of Giardia from humans for toxin production
in rabbits and found that these organisms did not produce toxins. To date, no
reports showing evidence for toxin production have been published. However, it
was suggested that Giardia excretory-secretory products may play a role in the
pathogenesis of giardiasis, either as a trigger for the diffuse brush border injury, or
via direct cytopathogenetic effects during close contacts between host cells and
trophozoites, and this needs to be investigated (Buret, 1994). Lysosome-like
vacuoles that line the surface of trophozoites have been identified (Feely et al.,
1984). These organelles have been shown to release numerous hydrolases,
including a thiol-dependant proteinase (Parenti, 1989). A possibility of secretion of
the proteinase has been indicated, although there is only limited evidence in
support of this. It was further suggested that under selected conditions, the
proteinase might be released into the extracellular milieu and play a role in the
pathogenesis of diarrhoeal disease (Parenti, 1989).
The association of giardiasis and allergic reactions have been documented.
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