Effect of Low Temperatures on Trophozoites of Giardia muris

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Abstract
Giardia muris trophozoites were placed in tubes containing a survival medium and subjected to low temperatures in the presence of various concentrations of glycerol. The parasite was able to survive freezing for 24 hours at 3 different temperatures and subsequent thawing. The optimum concentration of glycerol for survival at -38[plus or minus]5[degree]C was 14.2%. There was no trophozoite survival in any media lacking glycerol. Utilizing cotton as an insulating material to reduce the rate of cooling to -30[degree]C appeared to facilitate the survival of G. muris as did the addition of the surface active agent Tween 80. The parasites were able to survive in the frozen state for as long as 40 days and in some cases were able to survive thawing and refreezing. Limited experimentation indicated that the trophozoites, contrary to expectations, could survive quick freezing to -70[degree] C in a dry ice-alcohol bath.