Early in October 2016, the U.S. Department of Agriculture (USDA) was faced once again with New World screwworm, which had been eradicated from the United States more than three decades ago. Infestation of this flesh-eating parasite was confirmed in deer from the National Key Deer Refuge in the Florida Keys.
USDA’s Animal and Plant Health Inspection Service (APHIS) immediately began releasing sterile male flies in Florida’s affected areas as part of an aggressive eradication campaign. By March 2017, the screwworm had been successfully eradicated from Florida.
This success was a collaborative effort between USDA agencies and other federal, state and local agencies. The USDA team included Agricultural Research Service (ARS) scientists—experts on New World screwworm—who collected screwworm samples from affected animals for DNA analysis and for sending to a bio-secure research facility in Panama that produces sterile flies.
Screwworms can severely injure livestock and other warm-blooded animals, including humans. Renowned USDA entomologists Edward F. Knipling and Raymond C. Bushland first devised and tested the sterile-male-release approach to control screwworm in the 1950s. Since then, the method also has been used successfully to control other agricultural pests.
Today, USDA continues to lead the screwworm fight through strict pest monitoring standards and sound scientific research. Central to the success in vanquishing the screwworm is the mass-rearing of trillions of flies. Young males, made sexually sterile, are air-shipped to other facilities for screwworm control programs. Mating between native females and sterilized males produces no offspring and eventually leads to the pest’s eradication.
The screwworm eradication effort is a collaboration between USDA and the Panamanian government and extends through Panama, maintaining a barrier at the Darien Gap, next to Colombia. The Screwworm Production Facility in Pacora, Panama, continuously produces and releases sterile male screwworm flies to prevent northern migration of, and infestation by, Colombian screwworm.
USDA remains vigilant in keeping the screwworm out of the United States by releasing sterile flies and identifying, evaluating and investigating biological control agents for use against the screwworm and other invasive species.