Fact Check: U.S. previously eradicated New World screwworms in the 1960s.

Fact Check: "U.S. Previously Eradicated New World Screwworms in the 1960s"

What We Know

The New World screwworm, scientifically known as Cochliomyia hominivorax, is a parasitic fly that lays its eggs in the wounds of warm-blooded animals, leading to severe infestations known as myiasis. The United States successfully eradicated this pest in the 1960s through a program that utilized the sterile insect technique (SIT), which involved releasing large numbers of irradiated sterile males to mate with wild females, resulting in non-viable eggs (Gutierrez et al., 2019). The SIT program began in Florida in 1957 and expanded to Texas in 1962, with the last reported case of autochthonous screwworm myiasis in the U.S. occurring in 1982 (CDC, 2024). By 1966, the U.S. was officially declared free of indigenous screwworms (USDA, 2025).

Analysis

The claim that the U.S. eradicated New World screwworms in the 1960s is supported by multiple credible sources. The CDC confirms that the eradication efforts were successful by the late 1960s, highlighting the timeline of eradication in the U.S. and subsequent efforts in Mexico and Central America (CDC, 2024). Additionally, the USDA notes that the eradication program not only eliminated the pest but also significantly benefited the livestock industry, saving billions of dollars (USDA, 2025).

The primary method of eradication, the SIT, was particularly effective due to the mating habits of the screwworms, where females mate only once, allowing for a targeted approach to population control (Gutierrez et al., 2019). The success of the program is further corroborated by historical records indicating that by 1966, the U.S. had achieved a significant reduction in screwworm populations, leading to the declaration of freedom from the pest (Texas A&M, 2025).

While some sources acknowledge that non-autochthonous cases of screwworm myiasis can still occur in the U.S. due to reintroductions from endemic areas, these instances do not negate the fact that the pest was eradicated from the domestic environment during the 1960s (CDC, 2024).

Overall, the sources used in this analysis are reputable, including government publications and peer-reviewed articles, which lend credibility to the information presented.

Conclusion

Verdict: True
The claim that the U.S. previously eradicated New World screwworms in the 1960s is accurate. The successful eradication was achieved through a well-implemented SIT program, and the U.S. was officially declared free of the pest by 1966. While there are ongoing concerns about potential reintroductions, this does not undermine the historical fact of eradication.

Sources

1. Deconstructing the eradication of new world screwworm in ...
2. Resurgence of New World Screwworm in the Americas
3. Introduction · STOP Screwworms: Selections from the Screwworm ...
4. New World screwworm fact sheet - Texas A&M AgriLife Extension Service
5. 1958-1969 · STOP Screwworms - National Agricultural Library
6. Texas A&M AgriLife announces New World screwworm fact sheet
7. Federal officials working to keep U.S. free of nightmarish screwworms
8. PDF New World Screwworm Eradication Programs, by Start Date