Southeastern United States Collection: Screwworm Eradication Program Records

What is a Screwworm?

The scientific name of the New World screwworm, also commonly known as the American primary screwworm, is Cochliomyia hominivorax. Before its eradication from the United States the screwworm devastated livestock populations and cost ranchers and consumers millions of dollars.

Screwworms were a threat to the health of humans, livestock, and animals in the wild. Screwworm flies are attracted to open wounds, such as fresh cattle brands or the navels of newborn animals. Ranchers had to closely monitor their animals for wounds. They also took preventive measures by removing barbed wire and protruding nails from their land.

The screwworm lives for approximately 21 days in warm weather, but can maintain a longer life cycle in cooler climates. Although the male screwworm fly mates continually throughout its lifetime, the female fly mates only once, laying her eggs along the edges of wounds on warm-blooded animals. If the wound is not treated, the egg masses hatch into larvae, which burrow into the host's flesh--hence the name "screwworm"--and consume its living tissue and fluids. As the larvae feed, they enlarge the wound and attract additional female flies, which deposit their own egg masses into the wound. For several days the screwworm larvae feed on the host's flesh, gaining nourishment for the next stage in their development. If the wound remains untreated, secondary infections are nearly inevitable and it is unlikely that the host will survive.

After the screwworm larvae gain sufficient sustenance, they leave the host by dropping to the ground and burrowing shallowly into the soil. There they form a dry outer shell and enter the pupal stage. It is during this stage that the pupae metamorphose into adult flies. When the flies emerge from the ground they soon mate and the cycle begins again. Screwworm flies are blue-green, with three dark stripes on their backs, and orange eyes. They are about twice the size of a housefly.

Control and Treatment

Devil's Island, off the coast of French Guiana, was the site of the first reported screwworm case in 1858. It was not until 1933, however, that the screwworm fly was recognized as its own species. Emory Clayton Cushing, an entomologist with USDA's Bureau of Entomology and Plant Quarantine, and Walter S. Patton of the University of Liverpool, United Kingdom, are credited with establishing that the screwworm fly is not the same species as the more common blowfly (Cochliomyia macellaria), which feeds on dead animals. Following publication of this discovery, research began to focus on control of the pest.

Before 1933 the screwworm was concentrated in the southwestern part of the United States. A shipment of infested livestock brought the screwworm from the southwestern to the southeastern United States in 1933. County agents and researchers conducted numerous reports and surveys to assess the damage and to try to determine the living habits of the screwworm. In 1934, the screwworm could be found in Mississippi, Alabama, North Carolina, South Carolina, Georgia, and Florida as well as in the southwestern United Sates.

Initially, the only two effective wound treatments were benzol and pine tar oil. Benzol killed the worms while the pine tar oil repelled flies and aided in healing the wound. These treatments required daily application and confinement of the wounded animal. After further study, scientists developed a remedy which they named Smear 62. It was a thin paste formed from a combination of diphenylamine, benzol, turkey red oil, and lamblack. Although this worked better than the previous combination, it still did not kill the fly. A full scale eradication of the screwworm was needed.

Sterile Insect Technique

Two factors combined in the 1930s to form the basis for the USDA's Screwworm Eradication Program. These were Edward Fred Knipling's theory that the screwworm population could be eradicated by inundating the normal population with sterile males (known as the Sterile Insect Technique), and Raymond C. Bushland's development of a method for rearing large numbers of the insects for research on a diet of ground meat, beef blood, water, and a small amount of preservative, such as formalin, rather than having them feed on live animals. Researchers still needed to develop an effective method to sterilize the screwworm.

Between 1947 and 1950, scientists made unsuccessful attempts at chemical sterilization of the insect at the Kerrville, Texas, research laboratory. During this time the screwworm spread as far north as South Dakota via infested livestock shipments.

In 1950, Alfred W. Lindquist drew Knipling's attention to an article published in January of the same year by the Nobel Prize winner Hermann Joseph Muller. Muller's article investigated the sterilization of fruit flies by radiation and Knipling immediately saw this as a potential solution to the problem of mass sterilization of screwworm flies. Bushland arranged to use hospital x-ray equipment to test whether radiation could effectively and efficiently sterilize large numbers of screwworm flies. The experiment was a success, and cobalt-60 gamma ray equipment from Oak Ridge National Laboratory made the mass sterilization possible.

Sanibel Island and Curacao

At this time, tests began on Sanibel Island, just off the coast of Florida, utilizing the Sterile Insect Technique to eradicate screwworms from the island. Sterile flies were released in large quantities from airplanes, flies were trapped to determine the ratio of sterile to fertile, and wounded goats were monitored for screwworm infestations. On May 8, 1953, the Sanibel Island tests were terminated and the Sterile Insect Technique was pronounced a success. Due to a slight reinfestation of the island, however, it was decided that a location farther from the mainland was needed in order to determine whether a full-scale eradication program would be possible. In January of 1953, a letter from Benjamin A. Bitter, a veterinarian on the island of Curacao, Netherlands Antilles, to the director of the Bureau of Entomology and Plant Quarantine, brought this island to the attention of Knipling. Curacao is approximately 40 miles off the coast of Venezuela and the next closest island is 30 miles away. It was here that scientists truly achieved a successful eradication. They released flies from planes at a rate of 400 sterile males per square mile, per week. In ten weeks, screwworm flies were eradicated from Curacao.

Fly Production Facilities

A larger fly production plant was built in Bithlo, Florida, in 1956. In 1957, the Florida legislature appropriated funds for a full-scale Southeast Eradication Program. In 1958, a new plant was built in Sebring, Florida, that could produce 50 million sterile flies per week. Senator Holland called for an effective eradication program in his speech entitled, "Science Pays Off," presented at the dedication of the Sebring plant. Holland stated, "Although losses due to screwworm in the Southeast fluctuate from year to year, the annual losses in livestock production are estimated at $20 million, and according to all reports, last year was the worst we have experienced since this pest entered the Southeast twenty-five years ago."

The Southeast Eradication Program was deemed a success in 1959. Any further reinfestations that occurred were controlled and the focus of screwworm eradication turned toward the southwestern United States.

The Southeastern United States Collection: Screwworm Eradication Program Records comprise five and one half linear feet of the Screwworm Eradication Collection. The records begin in 1932, with initial eradication theories, research, and numerous land surveys, and end in 1960, after documenting a full-scale eradication program completed by the U.S. Department of Agriculture (USDA). Bulk dates span the 1950s. The records are in good condition with no restrictions on their use.

The collection, which is divided into five series, documents the methods for rearing and sterilizing flies; fly trapping; field testing on Sanibel Island, Florida, and Curacao Island, Netherlands Antilles; construction of and production from the fly production plants in Orlando (constructed during 1952-1953), Bithlo (1956) and Sebring (1958), Florida.

Correspondence (Series I) constitutes the bulk of the collection. The most notable communication is between scientists Alfred W. Lindquist, Raymond C. Bushland, Alfred H. Baumhover, and Edward Fred Knipling. Scientists Clinton C. Skipper, A. L. Smith, Gaines W. Eddy, Andrew J. Graham, and veterinarian Benjamin A. Bitter also feature in the communications. It is important to note that this series includes correspondence between USDA personnel and various individuals at other federal, state, and local government agencies, universities, and private corporations, all of whom were working to eradicate the screwworm.

All of the raw scientific data, surveys, maps, and authored reports which more formally present the retrieved data appear in Series II. The surveys include some information from screwworm eradication zones other than the southeast. Some of the reports have photographs and architectural drawings included.

The administrative materials (Series III) include information on funding, payroll, travel procedures, and safety materials. The materials used to inform and educate the public on the screwworm and the USDA's efforts to eradicate it from the Southeast are featured in Series IV. Series V consists of maps and blueprints detailing the screwworm rearing facilities in Florida.

Series I. Correspondence. 1930-1959. 6 boxes.

Contains correspondence between individuals and employees of the U.S. Department of Agriculture (USDA) involved in the Screwworm Eradication Program, as well as between program employees and individuals outside of the USDA. Correspondence within the USDA covers discussions regarding the evolution of the eradication effort from surveying the extent of the screwworm infestation across the southeastern United States to the eradication experiments in Curacao to the development of the eradication program in Florida. A substantial amount of the correspondence is between program employees and outside entities, including employees of other government agencies, state officials, university professors, and staff of private companies that developed and marketed treatments for the eradication of the screwworm. The correspondence takes the form of both typed and hand-written letters, memorandum, and telegrams. The series is arranged chronologically by date. Some items of various dates are grouped together in their original order to retain the thread of discussion. These groups are arranged chronologically by the earliest letter. Photocopies of the remaining correspondence in the group are placed in their proper chronological order throughout the series. There are also photocopies of correspondence from other series chronologically arranged within Series I.

Series II. Reports. 1932-1959. 3 boxes.

Contains reports regarding the program to eradicate screwworms from the southeastern United States. Some items have correspondence associated with them. Original correspondence is included with the reports in this series, and photocopies of the correspondence with a reference note are inserted into their appropriate location within Correspondence (Series I).

• Series II.A. Eradication Program Data. 1934-1959.
  Reports containing raw data and statistics from surveys and scientific studies. The bulk of the items are weekly reports documenting field collections of screwworms from the test eradication sites on Sanibel Island, Florida, and Curacao. Some of the data is in the form of correspondence. These materials are a part of Series II.A. because the intention of these items was to convey data. The materials are arranged chronologically.
• Series II.B. Maps. 1951-1959.
  Maps detailing both the areas of screw worm infestation and progress of eradication program. Maps are arranged chronologically.
• Series II.C. Authored Reports. 1932-1959.
  Reports providing detailed findings on surveys or studies pertaining to the eradication program. The reports dated pre-1950 represent the early efforts of the program investigating screwworm infestation and early tests of treatments for livestock. The majority of these early items were produced under the auspices of the F.E.R.A program in Mississippi. There are some reports that do relate to outbreaks of the screwworm in areas outside of Mississippi and the southeastern United States. Most of the reports dated after 1950 cover all aspects of the eradication effort, including treatment tests, infestation studies, eradication experiments, and the eradication program as it proceeded from Curacao to Florida. The reports are arranged chronologically.

Series III. Administrative Documents. 1934-1957. 1 box.

The Administrative Document series (Series III) contains materials created to oversee the administration of the Southeast Screwworm Eradication Program.

• Series III.A. Financial Materials. 1934-1957.
  Budgetary items covering payroll expenditures, program expenses and purchases, and proposed program budgets that were not created in the form of correspondence. Some items have correspondence associated with them. Original correspondence is included with their appropriate financial documents in this series, and place-holding copies of the correspondence with a reference note were inserted into their appropriate location within the correspondence series. The financial materials are arranged chronologically.
• Series III.B. Notes. 1953-1957.
  General materials containing administrative and program information that was hand-written and intended for personal reference. Notes are arranged chronologically.
• Series III.C. Safety Materials. 1957.
  Outlines for emergency procedures and a training film for screwworm facility. Materials are arranged chronologically.

Series IV. Official Program Materials. 1947-1959. 1 box.

Series IV contains materials produced by the Screwworm Eradication Program and other outside authors intended for public dissemination.

• Series IV.A. Press Releases and Public Information. 1947-1958.
  Press releases, public statements, and notices produced by the eradication program for public dissemination and outside publication. All items are arranged chronologically.
• Series IV.B. Proposals. 1951-1959.
  Formal proposals stating program needs, intentions, or justifications for program actions. The proposals are arranged chronologically.
• Series IV.C. Speeches and Presentations. 1952-1959.
  Written speeches and presentations made by program members regarding screwworm eradication efforts, or special events such as the opening of the Sebring fly factory. All items are arranged chronologically.
• Series IV.D. Published Writings. 1951-1957.
  Published materials produced both by the Southeast Eradication Program and by outside authors. Includes items authored by program members published in USDA serial publications, as well as items written by independent journalists. All writings are arranged chronologically.

Series V. Schematics. 1930-1956. 3 folders.

This series includes blueprints and floor plans of facilities built for the Screwworm Eradication Program in Florida. The materials are arranged chronologically.

Sources Used for Finding Aid:

Meadows, M. E. "Eradication Program in the Southeastern United States." Symposium on Eradication of the Screwworm from the United States and Mexico. College Park, MD: Entomological Society of America (Dec. 1985): 10.

Southeastern United States Collection: Screwworm Eradication Program Records. Special Collections, National Agricultural Library.

Special Collections, National Agricultural Library. "STOP Screwworms: Selections from the Screwworm Eradication Collection." Accessed November 17, 2005 from https://www.nal.usda.gov/exhibits/speccoll/exhibits/show/stop-screwworms--selections-fr.

Related Collections at the National Agricultural Library:

Artifacts: Screwworm Eradication Program Records. Manuscript Collection 348.

Audiovisual Materials: Screwworm Eradication Program Records. Manuscript Collection 215.

Baumhover, Alfred H., Papers: Screwworm Eradication Program Records. Manuscript Collection 266.

Graham, Owen Hugh, Papers: Screwworm Eradication Program Records. Manuscript Collection 213.

Husman, Chester N., Awards: Screwworm Eradication Program Records. Manuscript Collection 349.

International Collection: Screwworm Eradication Program Records. Manuscript Collection 355.

Knipling, Edward Fred, Papers: Screwworm Eradication Program Records. Manuscript Collection 210.

Oral Histories: Screwworm Eradication Program Records. Manuscript Collection 305.

Promotional Materials: Screwworm Eradication Program Records. Manuscript Collection 214.

Severn Run's Cazador (Caz), Screwworm Detection Dog, Collection: Screwworm Eradication Program Records. Manuscript Collection 310.

Southeastern United States Collection: Screwworm Eradication Program Records. Manuscript Collection 212.

Southwestern United States and Mexico Collection: Screwworm Eradication Program Records. Manuscript Collection 211.

USDA Entomology Research Division Records. Manuscript Collection 237.

Wyss, John, Papers: Screwworm Eradication Program Records. Manuscript Collection 338.