Light micrograph (phase contrast) of blood infected with parasitic protozoans, members of the Trypanosoma brucei group that cause African sleeping sickness (trypanosomiasis) in man & cattle. The organisms appear as elongated, ribbon- like objects, stained purple; numerous red blood cells appear grey. T.b.rhodesiense causes Rhodesian sleeping sickness primarily in cattle and is transmitted by the tsetse fly Glossina morsitans. T.b. gambiense, which causes Gambian sleeping sickness that mainly affecting man, is transmitted by G. palpalis. Magnification: X 320 at 35mm size.