Experimental and first generation vaccines against a number of protozoal diseases have been described (Table II), and it is likely that, of these, the sub-unit vaccines will be developed further to improve not only efficacy profiles but also production processes. Giardia, Babesia and Leishmania vaccines based on antigens from in vitro culture, for example, are likely to be developed into recombinant antigen vaccines (22). A recombinant sub-unit vaccine against Theileria spp. is probable in the near future (24).