Answer to Case 724

 Answer to the Parasite Case of the Week 724: Giardia duodenalis trophozoites and cysts.

Florida Fan eloquently described the characteristic motility pattern of Giardia trophozoites: "Beautiful autumn leaves falling in the wind in a sliding side to side motion." He also notes that "Giardia trophozoites and cysts can present a little challenge to parasitologists at times. Most of us are used to see the typical kite-shaped trophozoite with its nuclei, sucking disks and flowing flagella. When these trophozoites turn sideways, we may see only ạ leafy profile, and when they stand on their tails they will look like the kid next door poking his head over the privacy fence showing only the top of the head and the two eyes. The typical ovoid cysts can float on their ends and we may observe only a spherical object with a few discernible dots for nuclei. In my practicing days, I built models of both the trophozoite and the cyst and rotated them around to show the team the different morphology when viewed at different angles. Beautiful case indeed."  Thank you for the great imagery, Florida Fan!

Most people are familiar with the classic morphology of the trophozoites (and less so of the cysts), but we have to remember that not all organisms have a 'textbook' appearance. Here are the lovely images from this case:

 

Lastly, here is a cartoon by Dr. Nagi!