Fig. 1

The tsetse fly and its associated microorganisms. Tsetse flies can harbor multiple microbes, including the bacterial endosymbionts obligate Wigglesworthia, facultative Sodalis, parasitic Wolbachia and Spiroplasma, as well as a taxonomically diverse population of environmentally acquired enteric bacteria, a virus (salivary gland hypertrophy virus, SGHV) and protozoan African trypanosomes. All tsetse harbor Wigglesworthia, while the presence of Sodalis, Wolbachia, Spiroplasma, SGHV and trypanosomes is fly population dependent. Wigglesworthia, Sodalis and SGHV are transmitted to developing intrauterine larval offspring via maternal milk secretions, while Wolbachia is transmitted through the germline. Spiroplasma’s mode of vertical transmission is currently unknown. Pathogenic trypanosomes are acquired by tsetse when they feed on an infected animal. The parasites must then undergo a complex development cycle in the fly before they can be successfully transmitted to a new host, where they cause disease. (This figure is adapted with permission from Aksoy et al., 2013) [179]