FIG 2.

Light microscopy of parasite cultures. Synchronized stages of Plasmodium falciparum strain 3D7 were treated with ivermectin for 72 h. Samples were evaluated by microscopy every 12 h until 72 h, to observe the parasites’ morphology. Untreated parasites in the ring (a.1 to a.7), trophozoite (c.1 to c.7), or schizont (e.1 to e.7) stage were maintained in parallel. Ivermectin-treated ring-stage parasites became trophozoites, but parasites did not develop further to schizonts (b.2 to b.7). Ivermectin-treated trophozoites arrested their life cycle, not completing maturation to schizonts (d.2 to d.7). Schizonts treated with ivermectin released merozoites to infect new erythrocytes; the merozoites developed to rings and also arrested at the trophozoite stage (f.2 to f.7). All treated parasites were exposed to 100 nM (∼IC₅₀ value). In summary, ivermectin arrested the parasite cycle at the trophozoite stage, and parasites started to present a condensed and pyknotic morphology.