Trypanosome Transmission Dynamics in Tsetse

Abstract

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 it's tsetse host.

Figure 1

Diagrammatic Representation of the Interactions between Tsetse, Trypanosomes and the Obligate Symbiont Wigglesworthia. This figure represents the life cycle and metamorphosis of trypanosomes within the tsetse beginning with their introduction via an infective blood meal, followed by their escape from the peritrophic matrix into the endoperitrophic space and subsequent invasion of the salivary glands for transfer to a vertebrate host. The diagram also illustrates the localization of the obligate endosymbiont Wigglesworthia in tsetse’s bacteriome in the anterior midgut as well as its transmission into tsetse’s intrauterine larva in milk secretions. The viviparous reproductive physiology is depicted with an intrauterine larva and the large network of milk gland tubules that provide nutrients.