Answer to Case 571

Answer:Giardia duodenalis(a.k.a.G. lamblia, G. intestinalis) trophozoites with " falling leaf " or " tumbling " motility. Note that this is quite different than the " spiraling " motility ofChilomastix mesnili and the " jerky " motility ofPentatrichomonas hominis - two other flagellates - both non-pathogns - that may be seen in human stool specimens.As pointed out by Florida Fan, the motility is further enhanced by dark field videography, which makes everything more interesting. Thanks again to Idzi for the very cool videos!Santiago gave us further information on howGiardiatrophozoites move in the intestine to attach to the duodenal intestinal mucosa:After excystation in the small intestine, the trophozoites quickly swim towards the epithelium and attach forming a monolayer; this contributes to the pathology and allows the parasite to escape the turbulent flow of the small intestine and continue the life cycle in the human host.To achieve this, it uses a combination of movements involving its four pairs of flagella as well as its caudal region, and it is able to switch its motility from " free swimming " in the intestinal lumen, which is more rapid, to a " pre-attachment " pace which is slower and more stable, facilitating effective attachment to the intestinal epithelium in the desired location to form a monolayer.Lastly, Old One reminds us howAntonie van Leeuwenhoek was delighted when he took a lookat his own watery stoolSeeing For the very first timeAnimalculesâ€...
Source: Creepy Dreadful Wonderful Parasites - Category: Parasitology Source Type: blogs