Doxycycline is a viable alternative to tetracycline for use in insect Tet-Off transgenic sexing systems, as assessed in the blowflies Cochliomyia hominivorax(Dipteria:Calliphoridae) and Lucilia Cuprina(Diptera:Calliphoridae)

Authors: Arp, Alex; WILLIAMSON, MEGAN - NORTH CAROLINA STATE UNIVERSITY; VASQUEZ, MARIO - U.S. DEPARTMENT OF AGRICULTURE (USDA); QUINTERO, GLADYS - U.S. DEPARTMENT OF AGRICULTURE (USDA); VARGAS LOWMAN, AIDAMALIA - UNIVERSIDAD DE PANAMA; SAGAL, AGUSTIN - U.S. DEPARTMENT OF AGRICULTURE (USDA); SCOTT, MAXWELL - NORTH CAROLINA STATE UNIVERSITY

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/30/2024
Publication Date: 2/24/2024
Citation: Arp, A.P., Williamson, M.E., Vasquez, M., Quintero, G., Vargas Lowman, A., Sagal, A., Scott, M.J. 2024. Doxycycline is a viable alternative to tetracycline for use in insect Tet-Off transgenic sexing systems, as assessed in the blowflies Cochliomyia hominivorax(Dipteria:Calliphoridae) and Lucilia Cuprina(Diptera:Calliphoridae). Journal of Economic Entomology. https://doi.org/10.1093/jee/toae023.
DOI: https://doi.org/10.1093/jee/toae023

Interpretive Summary: Blowflies with parasitic larvae can be highly damaging to livestock production. Two species, the Australian sheep blowfly, Lucilia cuprina, and the New World screwworm, Cochliomyia hominivorax, both have extensive control programs that could be improved through the use of male-only transgenic strains. These strains have the potential of reducing costs through elimination of females early in development. The transgenic strains of these species are maintained in equal sex ratio colonies in the presence of tetracycline antibiotics, which add cost and possibly reduce fitness of the flies. Until recently tetracycline was used, though doxycycline is a viable alternative that is more stable and functions at lower dosages. In this article we evaluated the suitability of doxycycline for maintining colonies of these transgenic blowflies and if there were potential fitness benefits. We found that doxycycline could maintain transgenic strains at dosages up to 1000 times lower than tetracycline. Reduced doxycycline dosages did not improve fitness, but was a suitable alternative to tetracycline.

Technical Abstract: Transgenic insect strains with tetracycline repressible (Tet-Off) female-lethal genes provide significant advantages over traditional sterile insect technique for insect population control, such as reduced diet and labor costs and more efficient population suppression. Tet-Off systems are suppressed by tetracycline class antibiotics, most commonly tetracycline (Tc) or doxycycline (Dox), allowing for equal sex ratio colonies of transgenic insect when reared with Tc or Dox and male-only generations in their absence. Dox is a more stable molecule and has increased uptake than Tc which could be advantageous in some insect mass-rearing systems. Here, we evaluated the suitability of Dox for rearing Tet-Off male-only strains of Australian sheep blowfly, Lucilia cuprina, and New World screwworm, Cochliomyia hominivorax, and the effects of dosage on strain performance. For both species, colonies were able to be maintained with mixed sex ratios at much lower dosages of Dox than Tc. Biological yields of C. hominivorax on either antibiotic were not significantly different. Further reduction of Dox dosages in C. hominivorax diet did not affect biological performance, though rearing with 10 or 25 µg/ml was more productive than 50 µg/ml. Additionally, C. hominivorax mating performance and longevity were equal on all Dox dosages. Overall, Dox was a suitable antibiotic for mass-rearing Tet-Off female-lethal L. cuprina and C. hominivorax and was functional at much lower dosages than Tc.