Anatomy and mechanics of tsetse fly blood feeding.

Human African trypanosomiasis (HAT) is a neglected tropical disease transmitted by infected tsetse flies (Glossina spp.) in sub-Saharan Africa. Infected tsetse flies can transmit trypanosomes, including Trypanosoma brucei subspecies that cause HAT in humans, as well as other trypanosome species that cause animal African trypanosomiasis in domestic animals and infect wildlife. Tsetse flies feed on a broad spectrum of hosts, including humans, elephants, buffaloes, rhinos, hippos, turtles, and monitor lizards. To understand how the insects can penetrate such diverse skin types, we detailed the anatomical structures involved in tsetse blood feeding, their mechanical properties, and the forces exerted by the fly during probing. We found that the tsetse fly's feeding apparatus does not rely on exceptionally unique structures or extraordinary forces. Instead, the tsetse fly has evolved subtle yet highly efficient adaptations, which include a labellum equipped with arrays of small teeth. When combined with a robust retraction movement of the proboscis, these structures create lesions on various types of skin, thus facilitating blood pool feeding on a broad host spectrum.