Figure 1.

Life cycle of Trypanosoma brucei. When a tsetse fly vector has a blood meal from an infected human, parasites enter the midgut where mammalian bloodstream stumpy forms sense the lower temperature and different nutrient environment and differentiate into procyclic forms. These will further differentiate into epimastigotes that journey to and populate the salivary glands. The short epimastigotes in the salivary glands goes through a final differentiation in the fly into the infective metacyclic forms, which are injected during the next blood meal of the fly into the mammalian host. In the bloodstream of the mammalian host, metacyclic parasites differentiate into bloodstream forms, consisting of dividing slender forms and cell-cycle arrested (non-dividing) stumpy forms. These parasites can invade and hide within niche conditions in tissues, such as brain and adipose tissue. Purple cycling circle indicates the parasite forms in which endogenous circadian rhythms have been identified (Rijo-Ferreira et al., 2017a).