Department of Veterinary and Livestock Development, Ministry of Agriculture and Cooperatives, P.O. Box 670050, Mazabuka, Zambia; Department of Animal Health, Institute of Tropical Medicine, Nationalestraat 155, B-2000 Antwerp, Belgium; Livestock Services Limited, P.O. Box 24437, 00502 Karen, Nairobi, Kenya; Department of Parasitology, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, B9820 Merelbeke, Belgium; Department of Veterinary Tropical Diseases, Faculty of Veterinary Sciences, Private Bag X04, Onderstepoort, 0110, South Africa
Mbao, V., Department of Veterinary and Livestock Development, Ministry of Agriculture and Cooperatives, P.O. Box 670050, Mazabuka, Zambia, Department of Animal Health, Institute of Tropical Medicine, Nationalestraat 155, B-2000 Antwerp, Belgium; Berkvens, D., Department of Animal Health, Institute of Tropical Medicine, Nationalestraat 155, B-2000 Antwerp, Belgium; Dolan, T., Livestock Services Limited, P.O. Box 24437, 00502 Karen, Nairobi, Kenya; Speybroeck, N., Department of Animal Health, Institute of Tropical Medicine, Nationalestraat 155, B-2000 Antwerp, Belgium; Brandt, J., Department of Animal Health, Institute of Tropical Medicine, Nationalestraat 155, B-2000 Antwerp, Belgium; Dorny, P., Department of Animal Health, Institute of Tropical Medicine, Nationalestraat 155, B-2000 Antwerp, Belgium, Department of Parasitology, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, B9820 Merelbeke, Belgium; Van Den Bossche, P., Department of Animal Health, Institute of Tropical Medicine, Nationalestraat 155, B-2000 Antwerp, Belgium, Department of Veterinary Tropical Diseases, Faculty of Veterinary Sciences, Private Bag X04, Onderstepoort, 0110, South Africa; Marcotty, T., Department of Animal Health, Institute of Tropical Medicine, Nationalestraat 155, B-2000 Antwerp, Belgium
Theileria parva sporozoite stabilates are used for immunizing cattle against East Coast fever and in in vitro sporozoite neutralization assays. In this study, we attempted to identify a cheaper freezing medium and quantified the infectivity loss of sporozoites due to refreezing of stabilates, using an in vitro technique. Pools of stabilates prepared using Minimum Essential Medium (MEM), Roswell Park Memorial Institute (RPMI 1640), foetal calf serum (FCS) and phosphate-buffered saline (PBS) were compared. All were supplemented with bovine serum albumin except the FCS. RPMI 1640 was as effective as MEM in maintaining sporozoite infectivity while the infectivity in PBS and FCS reached only 59% and 67%, respectively. In a second experiment, a stabilate based on MEM was subjected to several freeze-thaw cycles including various holding times on ice between thawing and refreezing. Refrozen stabilate gave an average sporozoite infectivity loss of 35% per cycle. The results indicate that RPMI can be used as a cheaper freezing medium for T. parva stabilates and that refrozen stabilate doses need to be adjusted for the 35% loss of infectivity.