Since the turn of the century, certain parasitic diseases of livestock have frus trated efforts to bring them under control by vaccination techniques; East Coast fever and trypanosomiasis are two such diseases. East Coast fever (ECF) kills a half million cattle annually; and 3 million are killed each year by trypanosomia sis, which is widely spread over tropical Mrica. Together, these diseases have closed some 7 million square kilometers of land to livestock grazing-land that might otherwise support an additional 120 million head of cattle. In 1970 W.A. Malmquist of the U.S. Department of Agriculture, in collabora tion with K.N. Brown, M.P. Cunningham, and other associates at the East African Veterinary Research Organization in Kenya, succeeded in cultivating in vitro the protozoal organisms responsible for East Coast fever. This success, obtained utilizing tissue cultures, encouraged a number of organizations to support research on these parasites in an accelerated effort to develop field vaccines.weiterlesen