Studies of in vitro excystation of Cryptosporidium parvum from calves.

Studies of in vitro excystation of Cryptosporidium parvum from calves showed that sporozoite yields were optimum when oocysts were treated with sodium hypochlorite, then incubated at 37 degrees C for 60 min in the presence of taurocholic acid solutions at pH about 7.0. Trypsin was not required for excystation and high concentrations were inhibitory. Studies using protease inhibitors and direct assays for proteolysis failed to implicate proteolytic enzymes as effectors of excystation. The results suggest that Cryptosporidium uses excystation mechanisms that are different from those used by Eimeria spp.