New World Screwworm Detected In U.S. Livestock For First Time Since 1966
New World screwworms were found in a three-week-old calf in Zavala County, Texas, on June 3, 2026, the first U.S. case since 1966.[1]
By June 7, officials confirmed additional cases in Gillespie, Edwards, Zavala and La Salle counties in Texas.[1] A dog that had recently crossed from Mexico tested positive in New Mexico. USDA is releasing about 4 million sterile screwworm flies per week by air in the Texas detection area, with additional ground releases underway. Ranchers warn the outbreak is another hit amid high costs and a shrinking national herd.[1]
In March 2025, a stop-work order halted the U.S.-funded sterile-fly control program in Central America. The Panama-based barrier had released as many as 100 million sterile screwworm flies per week at full capacity as of 2025 to block northward spread. The parasite had reemerged in Costa Rica and Panama in 2023 and advanced through Mexico after the program stopped, removing the containment barrier. Texas Agriculture Commissioner Sid Miller criticized USDA for moving too slowly as the pest advanced, while Agriculture Secretary Brooke Rollins said cuts did not weaken the response.
Economist David Anderson of Texas A&M says the outbreak will likely discourage herd expansion and add pressure to already record beef prices. Eradication of screwworm from the United States provided annual economic benefits exceeding $900 million to the livestock industry in post-1966 estimates. Texas lawmakers have urged immediate congressional funding to boost sterile fly production and contain further economic damage to ranchers.
The mainstream summary does not mention the significant scale of the sterile insect barrier program that was halted in March 2025, which had been releasing up to 100 million sterile flies per week to prevent the northward spread of the screwworm. This cessation is crucial because it directly correlates with the resurgence of the pest in Texas, as highlighted by the American Society for Microbiology, which notes that lapses in international containment programs, including COVID-19 interruptions and illegal cattle imports, contributed to this outbreak. Additionally, while the mainstream account mentions the economic pressures on ranchers, it fails to specify that the eradication of the screwworm previously provided over $900 million annually in benefits to the livestock industry, a figure that underscores the potential economic devastation of this resurgence.
Furthermore, social media insights reveal a sense of urgency among Texas lawmakers and ranchers for immediate congressional funding to bolster sterile fly production, which the mainstream summary does not capture. The concerns expressed by users on platforms like BlueSky highlight the precarious state of the national cattle herd, currently at a 75-year low, indicating that the implications of this outbreak extend beyond immediate containment efforts to broader agricultural stability and food supply issues. These perspectives suggest a more complex and urgent narrative surrounding the outbreak than what was presented in the mainstream coverage.
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📊 Relevant Data
The sterile insect barrier program based in Panama released up to 100 million sterile New World screwworm flies per week at full capacity to prevent northward spread into Mexico and the United States.
New World Screwworm: Rise, Fall and Resurgence — American Society for Microbiology
USDA is currently releasing 4 million sterile New World screwworm flies per week aerially in the Texas detection area, with additional ground releases underway.
USDA Confirms New World Screwworm in Texas — USDA APHIS
Eradication of New World screwworm from the United States provided annual economic benefits exceeding $900 million to the U.S. livestock industry.
Introduction · STOP Screwworms — National Agricultural Library (USDA)
📌 Key Facts
- On June 3, 2026, New World screwworms were detected in a three-week-old calf in Zavala County, Texas, the first confirmed U.S. case since 1966.
- By June 7, 2026, additional cases were confirmed in Texas counties including Gillespie, Edwards, Zavala and La Salle, and in a dog in New Mexico that had recently crossed the border.
- A March 2025 stop-work order, issued as the Trump administration dismantled USAID, shut down the decades-old sterile-fly screwworm control program in Central America.
- Texas Agriculture Commissioner Sid Miller has criticized USDA for moving too slowly as the pest advanced north from Panama, while Agriculture Secretary Brooke Rollins insists the cuts did not weaken the response.
- Economist David Anderson of Texas A&M says the outbreak will likely discourage herd expansion and could add pressure to already record U.S. beef prices.
📰 Source Timeline (1)
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