Exploring antibiotic affects on New World screwworm to optimize Tet-off transgenic sexing systems

The New World screwworm, Cochliomyia hominivorax, is an economically important ectoparasite of warm-blooded animals. Screwworm has been eradicated from North and Central America with sterile insect technique (SIT) and a constant barrier zone is maintained along the Panama-Colombia border. Transgenic male-only strains are being developed to improve the effectiveness of the screwworm control using Tet-off gene regulation systems which utilize antibiotics to suppress the transgene expression in colony and maintain an even sex ratio. Rearing insects on diet containing antibiotics can have impacts on microbiome and at high dosages can cause mitochondrial stress. To ensure that transgenic screwworm strains meet the high standards of the SIT program we investigated the impacts of antibiotics on screwworm. We assessed biological yields, mating behaviors, microbiome changes, and gut gene expression patterns. Additionally, we investigated the feasibility of rearing transgenic screwworm doxycycline which can also be used to suppress Tet-off systems, though doxycycline can be used at lower dosages and is a more stable molecule than tetracycline making it more suitable for screwworm rearing conditions.