Answer to Case 800

Answer to the Parasite Case of the Week 800: Enterobius vermicularis (pinworm), numerous adult females seen, with eggs in the background.  

There was a lot of great discussion in this case! Florida Fan noted the lateral alae, which are one of the characteristic features of this worm. They are most prominent as cephalic inflations, but they continue along the length of the worm. Other classic features include the pin-shaped tail of the female worms, size, and location. We can't make out the eggs in these images, but Florida Fan noted that they would be flat on one side, and curved on the other (i.e., planoconvex).

Many of you asked about how the stunning image with the blue worms was obtained. In brief, it was obtained using simplified darkfield illumination on a stereo microscope, which provides high-contrast, images of unstained, transparent specimens by illuminating them against a black background. We use this stereo microscope to examine all worms and arthropods that are submitted to our laboratory, and I've been really impressed with it. It also provides traditional and oblique brightfield illumination (the latter is what Heather used for the other image). Feel free to contact me if you would like more information about the particular stereo microscope we use.

Thank you for celebrating the 800th Case with me!