Survival of Aegyptianella pullorum, Anaplasma marginale and various parasitic protozoa following prolonged storage in liquid nitrogen.

Various protozoa species were examined using in vivo and in vitro methods to determine their ability to survive prolonged periods of storage in liquid nitrogen. The following protozoan species were successfully recovered after they had been cryopreserved for a period over 10 years: Trypanosoma lewisi, T. cruzi, T. congolense, T. brucei, T. rhodesiense, T. gambiense, T. evansi, T. equinum, T. equiperdum, Leishmania donovani, Plasmodium berghei, P. praecox (relictum), Babesia rodhaini and B. canis. The longest survival period that has been successfully tested so far is between 5 and 7 years for Eimeria species, for monoxenically (A--C) and axenically grown E. histolytica cultures between 2 and 7 years and trichomonades, including Crithidia sp., between 6 and 8 years. Aegyptianella pullorum was successfully recovered after 6.97 years and Anaplasma marginale after 1.92 years. The freezing techniques are briefly described.