Answer to the Parasite Case of the Week 652: Strongyloides stercoralis L3 (filariform) larvae.
As nicely described by Luis, "We can see in photo 2 an esophagus almost as long as the intestine, the tail is sharp and has notches (photo 3)."
The notches are classic and can be seen in both the the Ziehl-Neelsen (ZN) stained preparation and wet prep (inset), (arrows).
The ZN stain had been performed to screen for acid fast bacilli (AFB). AFBs would stain bright red with the carbol fuchsin dye, whereas the larva is only stained here with the methylene blue counter stain.
This case goes well with last week's, in which we saw L1 (rhabditiform) larvae of S. stercoralis.
Thanks again to Idzi for donating this great case!