Extracellular like-gregarine stages of Cryptosporidium parvum.

The present study confirms the existence of extracellular stages of Cryptosporidiumparvum during in vitro culture on MDCK, HCT 8 and Vero cells as well as alveolar macrophages, by optic, Nomarski and transmission electron microscopy images. Extracellular trophozoite/gamont, stages in syzygy, zygotes and spores with eight sporozoites were seen in the supernatant of the cultures. The first ultrastructural images of extracellular stages of C. parvum are shown in this study. The morphology of these stages, which have characteristics similar to those of some gregarines, support the contention that Cryptosporidium has closer affinity with gregarines. It also supports the necessity of reconsidering the life cycle of Cryptosporidium and the classification within the coccidia.