Turkey Leucocytozoon Infection.: 2. Cryobiologic Preservation of Leucocytozoon Smithi Sporozoites

Abstract

Five different cryoprotective agents at various concentrations were evaluated for their effectiveness in preserving the infectivity of Leucocytozoon smithi sporozoites at low temperatures for an indefinite period of time as determined by the degree of parasitemia in inoculated turkey poults.Glycerol at concentrations of 10 and 5 percent, DMSO at 10 percent ethylene and trimethylene glycols at 2.5 percent, and propylene glycol at five percent when dissolved in medium 199 plus 10 percent fetal bovine serum yielded excellent sporozoite survival at a temperature of −196° C. When dissolved in medium 199 supplemented with 10 percent turkey serum, cryoprotection by those chemicals was less effective. In the absence of animal sera, sporozoite survival to freezing was very poor. Regardless of suspending media, all sporozoites frozen by direct immersion in liquid nitrogen lost their infectivity. No differences were observed in the parasite’s prepatent period, time of maximum gametocyte density, nor RBC count pattern between turkey poults infected with frozen, stored sporozoites and those infected with fresh unfrozen sporozoites from the same original stock.