Early Immunological Responses Upon Tsetse Fly–Mediated Trypanosome Inoculation

African trypanosomiasis is a neglected tropical disease of medical and veterinary importance, caused by extracellular protozoan parasites of the genus Trypanosoma. The transmission of these parasites heavily relies on a range of tsetse fly species (Glossina sp.) in which the parasites differentiate into infective forms in the salivary glands or mouthparts of the insect. Infections are initiated through bites of infected flies, which results in a breach of the host skin as anatomical barrier and inoculation of parasites together with tsetse salivary factors into the dermis. In this micro-environment, parasites have to survive and promptly adapt in order to establish an infection and to colonize host blood. Yet, our current knowledge on the trypanosome development and immune interactions at this crucial early parasite–host interface is highly limited. In this chapter, we present the state-of-the-art knowledge of the early parasitological and immunological features of tsetse fly–mediated trypanosome inoculation in the dermis. This chapter will also discuss intrinsic and co-opted strategies that parasites use, through the escape or modulation of immune responses and the action of tsetse salivary components, to overcome early elimination by the host immune system.