<i>Spiroplasma</i> infection in colonized <i>Glossina fuscipes fuscipes</i> : impact on mass rearing and the sterile insect technique

Tsetse flies (Glossina spp.) can vector the parasites (Trypanosoma spp.) that cause the socioeconomically devastating neglected tropical diseases human and animal African trypanosomoses. In addition to this parasite, tsetse can harbor four genera of endosymbiotic bacteria, including Wigglesworthia, Sodalis, Wolbachia, and Spiroplasma, which are functionally crucial for the fly's physiological homeostasis and/or are potentially useful for the development of disease control strategies. Recent discoveries indicate that Spiroplasma infection negatively impacts tsetse fecundity. Conversely, housing the bacterium can benefit its fly host by making it unusually refractory to infection with parasitic African trypanosomes. In this study, we assessed the physiological impact of Spiroplasma infection on a laboratory colony of Glossina fuscipes fuscipes (Gff). For this purpose, two distinct Gff colonies were established: a Spi- colony that harbors a low Spiroplasma infection prevalence and a Spi+ colony that harbors a high Spiroplasma infection prevalence. Fitness parameters for both colonies revealed no significant differences in the length of larval development, adult eclosion rate, and flight propensity. However, flies from the Spi+ colony presented with lower fecundity and higher overall mortality than did individuals from the Spi- colony. Furthermore, males from the Spi- colony exhibited a competitive mating advantage over their Spi+ counterparts in a field cage setting. These findings have potential implications for the improvement of mass-rearing of Gff for sterile insect technique (SIT) applications.