Cryopreservation of Babesia caballi cultures

Babesia caballi cultures were cryopreserved with a solution of 10% (w/v) polyvinylpyrrolidone 40 as cryoprotectant. Samples were cooled at rates of 1, 10, 30 and 100 degrees C min-1 using a programmable freezer. Additionally, a styrofoam box designed to cool samples at an approximate rate of 10 degrees C min-1 when placed in a -80 degrees C freezer was used. Samples were stored in liquid nitrogen, thawed rapidly and inoculated into cultures. Although, a high loss of infectivity was observed after cryopreservation, cultures could be initiated reliably from cryo-stabilates frozen at a rate of 10 and 30 degrees C min-1 or frozen with the styrofoam box.