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Abstract

The short-term in vitro cultivation of intraerythrocytic stages of Thai isolates of the Theileria parasite was successfully established in this study. Of the four types of culture media used in the experiment, M199 supplemented with 40% fetal bovine serum (FBS) proved to be the best medium. The mean percentage of living parasites cultured in this medium was significantly higher than that in the others, ie, M199+fetal calf serum (FCS), RPMI+FBS and RPMI+FCS (p<0.05). In addition, many developmental stages, ie, match form, ring form, and 2-piroplasm, 3-piroplasm and 4-piroplasm forms, were observed at significant numbers in M199+FBS medium after 48-72 h of cultivation. It was also demonstrated in this study that the blood samples with a high percentage of parasitemia, ie, >4.5%, should not be cultured at cell suspension concentrations higher than 12.5%, whereas those with low percentage of parasitemia, ie, <4.5%, could be cultured at any percentage of cell suspension. On the other hand, our results revealed that culturing at approximately 12.5% cell suspension provided the highest percentage of both multiplied form and living parasites. Production of an optimal cultivation system that would lead to the successful continuous in vitro cultivation of intraerythrocytic stages of Theileria parasite remains to be investigated.