We have successfully maintained Cryptosporidium muris by cryopreservation. Oocysts were suspended in distilled water, stored at - 20 degrees C for 24 hrs, and then cryopreserved at -70 degrees C. Cryopreserved specimens were slowly thawed at 5 degrees C. Oocysts, which had been cryopreserved for 15 months without cryoprotective agents, retained their infectivity by the mouse titration method. Oocysts stored at 5 degrees C in 2.5% potassium dichromate failed to retain their infectivity beyond 6.5 months.
