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Photo: Sterile male screwworm fly marked with a numbered tag to study fly dispersal, behavior, and longevity. Link to photo information
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Screwworm larva
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USDA Celebrates Research That Eradicated the Screwworm

By Alfredo Flores
August 28, 2002

TUXTLA GUTIERREZ, MEXICO, Aug. 28--U.S. Department of Agriculture officials today joined Mexican agriculture officials in commemorating the 30th anniversary of the Mexican-American Commission for the Eradication of Screwworm and in recognizing the commission's success in eradicating the pest from the United States and Mexico.

"The successful eradication of the screwworm from the United States and Mexico has saved numerous lives and prevented countless losses in the livestock industry throughout North America," said Agriculture Secretary Ann M. Veneman. "The commission should be commended for its valiant efforts and resounding success--not only in these two nations, but throughout Central America as well."

On Aug. 28, 1972, the Mexican-American Commission for the Eradication of Screwworm was formed at the request of Mexican livestock producers, to carry the program south to the Isthmus of Tehuantepec. The commission, made up of an equal number of members from Mexico and the United States, includes USDA employees from the Animal and Plant Health Inspection Service (APHIS).

Working with the commission, APHIS managed to establish a barrier at that point in 1984, but cases remained in Mexico until 1986. The Mexican-American commission, in cooperation with other commissions formed with each Central American country, has eradicated the screwworm from virtually all of Central America down to the Isthmus of Panama. Today a permanent sterile fly release barrier is maintained in Panama between the Panama Canal and the Colombian border.

The commission eradicated the pest through methods including sterile fly dispersal, surveillance, quarantine, and wound treatment. The principle approach still used in this eradication program is the sterile insect technique (SIT), a form of biological control.

USDA's Under Secretary for Marketing and Regulatory Programs Bill Hawks is leading the USDA delegation and is speaking at today's International Screwworm Symposium and Celebration Day.

Edward F. Knipling
Edward F. Knipling developed the sterile insect technique. More about Knipling...

The Acting Administrator of USDA's Agricultural Research Service (ARS), Edward B. Knipling is also addressing symposium participants. His father, the late ARS entomologist Edward F. Knipling, along with the late ARS entomologist Raymond C. Bushland, developed SIT to suppress screwworms by sterilizing male flies with low-dose irradiation and releasing them to mate with fertile females. Such matings do not produce fertilized eggs, so numbers of insect offspring plummet dramatically.

Other speakers included retired Congressman Kika de la Garza (D-Texas), who served 13 years as Chairman of the House Agriculture Committee; Dr. Gustavo A. Rodriguez Heres and Dr. John B. Welch, current directors of the commission; and U.S. Ambassador to Mexico Jeffrey Davidow.

The commission worked with partners such as the Southwest Animal Health Research Foundation (SWAHRF) to successfully eradicate the screwworm from the United States.

USDA officials estimate that U.S. livestock producers benefit by more than $900 million each year from the screwworm eradication program.

The National Agricultural Library (NAL) has produced a 10' by 10' exhibit for the symposium and distributed a CD-ROM and brochures from its Special Collections--all of which describe the story of screwworm eradication. More information on NAL's Screwworm Eradication Collection can be found at:

Screwworms are parasites that can cause great damage to domestic livestock and other warm-blooded animals. The larvae of this pest enter open wounds of the host animal and feed on the raw flesh. Rare cases of humans being infested with screwworm have been reported. The United States has been free of screwworm since 1966.