Researchers Use New Method To Develop Genetically Sterile Screwworms

Genetically sterile screwworms being developed by a new method.

Sterile male screwworm fly marked with a numbered tag to study fly dispersal, behavior and longevity. Photo Credit: Peggy Greb.

Source: Agricultural Research Service

Scientists are developing transgenic sterile, male-only screwworm flies that could eliminate the need for the expensive irradiation technique now used in screwworm control programs, according to the Agricultural Research Service, the scientific research agency of the U.S. Department of Agriculture.

Sterile insect techniques are used to control pests such as screwworms, Cochliomyia hominivorax, Mediterranean fruit flies and tsetse flies, among others. Screwworm eradication efforts in particular save U.S. livestock producers about $900 million annually in potential losses, according to the ARS.

The ARS team involved with the project include entomologists Margaret Allen and Steven Skoda and geneticist Alfred Handler. Allen is at the ARS Biological Control of Pests Research Unit in Stoneville, Miss.; Skoda is a research leader with the ARS Livestock Insects Research Laboratory at Kerrville, Texas; and Handler works at the ARS Insect Behavior and Biocontrol Research Unit in Gainesville, Fla.

Using a genetic element called a “piggyBac transposon” as a vector, the researchers introduced a green fluorescent protein gene (GFP) into the genomes of eight screwworm strains. When viewed under ultraviolet light, the transgenic screwworms emitted a fluorescent glow, helping confirm GFP’s activation, according to ARS.

The research also revealed that transgenic male flies were as competitive as wild-type males in caged mating experiments. This is a plus compared to irradiated male flies, which have been shown to be less competitive than wild-type males. Irradiating screwworms is also said to be costly.

The ARS contends that once male-only screwworms are developed using the same transformation method as that used for the GFP strain, the next phase would explore inducing genetic sterility in the flies, which theoretically would eliminate the need for irradiation. Their field release, however, would hinge on an environmental impact assessment and regulatory approval, according to the ARS.

The research appears in the journal Medical and Veterinary Entomology.

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