Freezing Excysted Coccidial Sporozoites

• Published in: The Journal of parasitology 1969-12, Vol.55 (6), p.1229-1233
• Main Author: Doran, David J.
• Format: Article
• Language: English
• Subjects: Apicomplexa - drug effects; Cell culture techniques; Chemical suspensions; Cooling; Dimethyl Sulfoxide - pharmacology; Eimeria; Freezing; Melting points; Oocysts; Parasitology; Room temperature; Sporozoites; Temperature; Thawing; Time Factors
• ISSN: 0022-3395; 1937-2345
• DOI: 10.2307/3277262

Excysted sporozoites of Eimeria adenoeides, E. mivati, and E. tenella were placed in media containing different concentrations (2.5, 5, 7.5, 10, 12.5, and 15%) of dimethyl sulfoxide (DMSO). In the absence of freezing, survival of sporozoites was better at the lower concentrations. However, after sporozoites were frozen with a cooling rate of 1°/min from 25 to 26 C to -30 C and 10°/min from -30 C to -80 C, survival was better at the higher concentrations. With 10% DMSO for E. tenella and 12.5% for E. adenoeides and E. mivati, sporozoites were frozen using (1) equilibration periods of different lengths (20 to 50 min) and (2) different cooling rates (1, 3, and 5°/min) from the beginning of the procedure to the freezing point and from freezing to -30 C. The rate from -30 to -80 C was always 10°/min. Best results with all 3 species (more than 70% survival) were obtained when the equilibration period was 45 to 50 min and the cooling rate from the freezing point to -30 C was 1°/min. The cooling rate from beginning to the freezing point was not important; no differences in survival were found after using different rates, and sporozoites withstood an abrupt temperature drop to 4 C. Attempts to increase the survival of sporozoites in media containing 2.5, 5.0, and 7.5% DMSO by increasing the equilibration period to as long as 2.5 hr were unsuccessful.