Determination of parasitaemia. Parasitaemia was determined in peripheral blood in all groups of mice every other day, starting ten days after the beginning of daily mosquito bites. Average parasitaemias are shown for each group. Parasitaemia in the group subjected to normal mosquito bites (black squares) and immunized followed by normal mosquito bites (black circles) are shown. In the groups subjected to irradiated mosquito bites (white circles) and immunized control (white squares) no infected erythrocytes were detected. Error bars represent standard deviation within groups of mice (*, P < 0.05; **, P < 0.01, when comparing mice subjected to normal mosquito bites and immunized followed by normal mosquito bites mice using ANOVA).