Stearoyl-CoA desaturase is an essential enzyme for the parasitic protist Trypanosoma brucei

► Inhibiting Δ9 desaturase drastically changes T. brucei's fatty-acid composition. ► Isoxyl specifically inhibits the Δ9 desaturase causing a growth arrest. ► RNA interference of desaturase expression causes a similar effect. ► Feeding T. brucei-infected mice with Isoxyl decreases the parasitemia. ► 70% of Isoxyl-treated mice survived the trypanosome infection.