Answer to Case 786

 Answer to the Parasite Case of the Week 786: Cystoisospora belli

Idzi nicely described this finding as an "Immature oocyst of Cystoisospora belli (formerly known as Isospora belli) containing only one sporoblast, which will evolve to two sporoblasts and later on will sporulate to become infective." 

While we don't know the definitive details of the images that Dr. Bradbury provided, Idzi suggested that "the last one could be autofluorescence at 450-490 nm." and noted that "All coccidia (including Cystoisospora belli) will demonstrate fluorescence (without prior staining) when placed under UV-light. They will show up as bright blue structures when using an excitation filter of 330-365 nm, or green at 450-490 nm. Of note: Cryptosporidium is not placed among the coccidians anymore (moved to the Gregarines), and does not demonstrate autofluorescence either!"

If you are interested about how autofluorescence can be used for diagnosis, you should check out Blaine's and Dr. Marc Couturier's recent paper "Shedding new light on Cyclospora: how the use of ultraviolet fluorescence microscopy can improve diagnosis of cyclosporiasis".