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International Screwworm Program
The screwworm is the larval stage of the fly cochlyomyia hominivorax (coquerel or man eater) that feeds on tissues and fluids of living animals including man.
The female fly mates only once (male mate up to 10 times) and lays multiple batches of 300 or more eggs on the edge of the wound. Eggs hatch in 12 hours and the larvae feed on the wound for 5-7 days, then drop on the ground to pupate. After 7 days fly emerges and is ready to mate after 2 days later.
Economic loses from death, weight loss susceptibility to other diseases and the labor costs to inspect animals can be great.
A research team proposed that if large numbers of male screwworm flies could be sexually sterilized and dispersed over infested areas to mate with native female flies, natural reproduction could be stopped if the eggs produced were not fertile.
After intensive research in USDA’s laboratory in Kerrville, Texas, it was found that screwworm pupae, just before emerging as flies, could be sexually sterilized by exposure to radiation using Cobalt-60 or X-rays as the radioactive source.
In 1954, this “sterile insect technique” was tested on the small island of Curacao, about 80 kilometers off the northeastern coast of South America. After four months, Screwworms were eliminated.
Following the successful Curacao experiment, livestock producers in the Southeastern United States requested of their respective state governments and the Federal Government that an eradication program be conducted in their region. Using sterile flies reared in a plant in Sebring, Florida, a joint State-Federal program began in 1958 and by 1960, Screwworm had been eradicated. The two-year campaign cost about $11 million, eliminating the annual $20 million losses caused by Screwworms.
Following the success of the program in the southeastern part of the United States, cattle producers in the southwest requested a similar eradication program. The elimination of this destructive pest would end losses estimated at more than $100 million annually.
A sterile fly production plant was constructed near Mission, Texas, financed in part with funds donated by cattle producers through the Southwest Animal Health Research Foundation (SWAHRF). The plant was capable of producing more than 150 million sterile flies per week for dispersal over infested areas of Texas, New Mexico, Arkansas, Louisiana, and Oklahoma. The program was later extended to include Arizona, California and based on an agreement between Mexico and the United States, the northern states of Mexico
Last Modified: January 25, 2007