Researchers Control Parasitic Fly Populations by Releasing Modified Males

Researchers have found a new way to combat New World screwworm flies, parasites that prey on livestock. By withholding tetracycline from developing fly larvae, the research team was able to breed males that only produce male larvae after mating. This will eventually result in a population of only male flies, an inexpensive way of eradicating the pests. The findings are in a paper just published in the journal BMC Biology.

New World screwworm flies (Cochliomyia hominivorax) are parasitic pests that feed on the living tissue of mammals, including humans. They cause major livestock losses in the subtropical and tropical regions of the Western hemisphere. The flies have already been eliminated in other areas through sterile insect programs. The programs involve using irradiation to sterilize flies. The flies are then released to mate with fertile flies. While effective, sterile insect programs can be expensive to operate.

A team of researchers used genetic modifications to breed a special line of screwworm flies. When tetracycline is withheld from these flies when they’re developing, the males will only produce more males as adults. The males will mate with fertile females but since only males will be produced, the population will drop. By releasing these special males, the team can accomplish results similar to sterile insect programs while saving time and money.

The livestock industry loses billions of dollars from screwworm fly parasitism. Sterile insect programs can control screwworm fly populations but are expensive to run. The authors of the study propose an alternative: releasing modified males that only produce more males after mating. The simple technique could even be applied to other pests, including the Old World screwworm. A similar male-only release program successfully controlled another pest species, the Mediterranean fruit fly. The researchers are hopeful that their findings could prevent livestock losses and screwworm attacks on humans.


Carolina Concha et al. A transgenic male-only strain of the New World screwworm for an improved control program using the sterile insect technique. BMC Biology (2016).

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