To describe the development of the asexual blood stages of PBANKA_1229000 KO lines we determined the course of infection in Swiss Webster and C57Bl/6 mice following either inoculation with sporozoites or intraerythrocytic stages. An apparent trend (but not statistically different) towards long survival was observed in Swiss Webster mice or C57Bl/6 mice that were intravenously (i.v.) injected with 10(4) and 10(5) schizonts (Swiss Webster mice) or 10(3) or 10(4) mixed asexual stages (C57Bl/6 mice) of PBANKA_1229000 KO parasites. When we monitored the survival of mice after i.v. inoculation of 1,000 P. berghei ANKA wt or PBANKA_1229000 KO sporozoites, we observed a longer survival time of mice infected with PBANKA_122900 KO than those infected with wt parasites, which is in support of the above mild growth delay of asexual blood stages. We did not detect differences in reticulocyte versus normocyte preference or a lower production of merozoites per schizonts