CRYOPRESERVATION AND STORAGE OF PARASITIC PROTOZOA IN LIQUID-NITROGEN

In 1961 I reported the first successful attempt to cryopreserve and store protozoa in liquid nitrogen. In this presentation, drawing on more than 30 years of personal experience, I discuss the factors which I consider to be most critical to the successful preservation and long term storage of several species of parasitic protozoa in liquid nitrogen. I then present my most successful protocol for cryopreservation of these parasites. Finally, I cite some longevity records for a variety of protozoa stored in liquid nitrogen vapor at the Laboratory of Parasitic Diseases. The oldest record is for a monoxenic culture of Entamoeba histolytica grown in association with Crithidia fasciculata that was frozen on January 6, 1961. Thirty-two years and 11 months later both parasites were recovered and used to initiate new culture lines.