Bulk-freezing of Theileria parva stabilates for vaccine production.

The freezing and thawing characteristics of different volume samples of freezing medium and Theileria parva stabilates were studied in order to identify suitable conditions for freezing large volumes of stabilates for use in the preparation of vaccines. Conventionally, 1.8 ml aliquots are used but are cumbersome to handle in the field preparation of trivalent vaccines. In this study, 75 ml aliquots of the stabilates were found to exhibit freezing and thawing characteristics similar to those of the 1.8 ml aliquots. Bulk freezing of 2 stabilates yielded sporozoites which remained infective for cattle upon thawing, induced a range of clinical reactions in vaccinated cattle and stimulated the development of immune reactions.