Trypanosome transmission dynamics in tsetse

• We describe tripartite interactions between tsetse, trypanosome and symbionts.
• Tsetse undergo intrauterine larvagenesis and lactate (viviparous reproduction).
• Fecundity relies on obligate symbiont for diet supplementation and proline synthesis.
• Symbiont presence during larval growth influences adult immune and gut development.
• Gut peritrophic matrix barrier integrity affects trypanosome transmission dynamics.

Tsetse flies (Diptera: Glossinidae) are vectors of African trypanosomes. Tsetse undergo viviparous reproductive biology, and depend on their obligate endosymbiont (genus Wigglesworthia) for the maintenance of fecundity and immune system development. Trypanosomes establish infections in the midgut and salivary glands of the fly. Tsetse's resistance to trypanosome infection increases as a function of age. Among the factors that mediate resistance to parasites are antimicrobial peptides (AMPs) produced by the Immune deficiency (Imd) signaling pathway, peptidoglycan recognition protein (PGRP) LB, tsetse-EP protein and the integrity of the midgut peritrophic matrix (PM) barrier. The presence of obligate Wigglesworthia during larval development is essential for adult immune system maturation and PM development. Thus, Wigglesworthia prominently influences the vector competency of its tsetse host.