Theileria annulata is an intracellular parasite. It causes tropical theileriosis. It is transmitted by ticks in the genus Hyalomma. Infection by Theileria causes a lymphoproliferative disease in cows with clinical features similar to some human leukemia. T. annulata infects mainly bovine B cells and macrophages. Theileria-infected cells are transformed and immortalized; they display uncontrolled proliferation in vitro, independent of exogenous growth factors, and increased ability to migrate and form metastases in immunodeficient mice. Interestingly, Theileria-dependent transformation is reversible; animals are mostly cured upon treatment with the theilericidal drug Buparvaquone. To achieve transformation, the parasite manipulates the host cell signaling pathways that control cell proliferation and survival. Our understanding of host cell transformation by Theileria annulata is still in nascence. In our lab we are trying to understand the role of heat shock proteins in the life cycle of this parasite.