msp7 infected BALB/c mice showed only a mild delay in the parasite growth rate during the initial phase of infection. The mice progressively developed a high parasitemia and died during the third week post infection similarly to wild type-infected mice.In C57BL/6 mice, msp7 parasites showed a significant reduction of the growth rate up to day 12 post infection and failed to induce signs and symptoms of ECM. These mice showed a prolonged course of infection with increasing parasitemia and died during the fourth week post infection with a peak parasitemia reaching 70%. All wild type-infected mice died at around day 8 post-infection when the parasitemia was still low (around 20%) developing a typical ECM pathology. The virulence attenuated phenotype of msp7 parasites varied with the mouse strain used. A substantial fraction of infected msp7 CD1 mice (about 60%) died within 10 days post-infection with signs and symptoms of ECM and with a parasitemia below 15% while the others mice died later of severe anemia.

Mutant blood stages show a minor growth defect resulting in a lower growth rate in BALB/c mice during the initial phase of infection (day 8/10). At later stages of infection (when reticulocytes are prevalent), the growth rate was similar to that of wild type parasites. In aged WISTAR rats (15 weeks) the mutant blood stages showed a reduced growth and virulence phenotype.

Mutants show a minor growth defect resulting in a lower growth rate in Balb/c mice during the initial phase of infection. When reticulocytes were prevalent (after day 9 after infection), the growth rate was similar to that of wild type parasites