Screwworm outbreak poses $1.8 billion economic threat to Texas
Screwworm outbreak threatens Texas economy with estimated $1.8 billion in costs.
Event / Disaster
New World Screwworm US Detection
First confirmed New World screwworm case in the United States since 1966 detected in Texas calf near Mexico border on June 4, 2026. Detection triggered emergency response including quarantine zone, sterile fly releases, and federal eradication infrastructure investment as parasite advances northward from Panama.
7 reported locations
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2026-08-16 to 2026-11-13 · UTC publication dates
Coverage begins 5 Jun, 01:30 UTC
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What happened
USDA Secretary confirms U.S. food supply remains safe despite screwworm detection
USDA Secretary Brooke Rollins assured the public that the U.S. food supply remains 100 percent safe following the screwworm detection. She noted that screwworms do not infest meat, fruits, vegetables, or other food sources—only livestock. The screwworms do not contaminate food products.
New World screwworm eradicated in U.S. cattle in 1966 through sterile insect technique
The United States successfully eradicated the New World screwworm from its livestock population in 1966 using the sterile insect technique. This involved releasing sterile male flies in Panama that mated with wild females, causing population collapse. The technique was wildly successful in eliminating the pest from the U.S. and Mexico.
New World screwworm outbreak in Mexico affects over 26,000 cattle since 2022
Mexico has recorded at least 26,216 screwworm cases across livestock since the outbreak began. As of the reporting date, more than 2,700 cases remain active. The outbreak has been spreading northward through Central America since at least 2022.
U.S. closes livestock ports to Mexico as precaution against screwworm
All southern U.S. ports of entry have been closed to livestock trade from Mexico as a precautionary measure to prevent the spread of New World screwworm into the United States. The closure began before the Texas detection was confirmed.
USDA accelerates release of sterile New World screwworms to combat infestation
The U.S. Department of Agriculture expedited the targeted ground release of sterile New World screwworm flies in the affected area as part of eradication efforts. The agency was already releasing 4 million sterile flies per week by air in the region, and increased the effort with additional ground releases. The sterile insect technique involves releasing sterilized male flies that mate with wild females, causing the population to collapse.
USDA establishes 20-kilometer quarantine zone around screwworm detection site in Texas
The U.S. Department of Agriculture and Texas Animal Health Commission formed an Incident Command Team and established a 20-kilometer infested zone around the detection site in Zavala County with quarantines and movement controls for livestock. The zone implements surveillance protocols and movement restrictions.
New World screwworm detected in Texas calf for first time in 60 years
The U.S. Department of Agriculture confirmed the detection of a New World screwworm in a 3-week-old calf in Zavala County, Texas. Larvae were identified in the calf's umbilical area. This is the first confirmed case of the parasitic fly in U.S. livestock since the species was eradicated in 1966.
Economic impact of screwworm outbreak estimated at $1.8 billion for Texas alone
Experts estimate that an outbreak of screwworm could cause approximately $1.8 billion in damages to Texas's economy. The infestation would likely shrink the cattle supply and inflate beef prices across the nation.
First human case of New World screwworm confirmed in U.S. international traveler
In August 2025, the U.S. reported the first confirmed human case of New World screwworm infection in an international traveler. The individual recovered from the infection, and investigation found no evidence of transmission to other people or animals.
New World screwworm detected 25 miles south of Texas border in Mexico
A New World screwworm case was confirmed in Coahuila State, Mexico, approximately 25 miles south of the Texas border. This detection preceded the Texas case and demonstrated the northward spread of the parasitic fly through Central America and Mexico.
New World screwworm eradicated from United States in 1966
The New World screwworm was successfully eradicated from the United States in 1966 through a concerted effort using the Sterile Insect Technique, which involves releasing large numbers of sterilized male flies to prevent breeding. The eradication program was expanded throughout Central America, and the screwworm was declared eradicated from Panama in 2006.
Texas Governor Abbott declares state disaster for screwworm threat
In August 2025, Texas Governor Greg Abbott issued a rare statewide disaster declaration and activated emergency powers in anticipation of the New World screwworm crossing the Mexico border into Texas.
USDA dedicates $21 million to screwworm fly breeding facility in Mexico
The USDA converted a fruit-fly breeding facility in southern Mexico into a screwworm breeding facility with $21 million in funding. The facility is expected to become operational the following month. Additionally, the USDA opened a new center for dispersing sterile flies in southern Texas and began construction on a $750 million screwworm fly production facility.
USDA closed U.S.-Mexico border to livestock imports from Mexico
The USDA closed the U.S.-Mexico border to livestock imports from Mexico to prevent screwworm introduction. The closure was implemented in response to the northward migration of the parasite through Mexico and Central America.
USDA initiates sterile insect technique to combat screwworm infestation
The USDA is deploying sterile male screwworm flies into the quarantine zone using ground-release chambers, in addition to 4 million sterile flies already being released aerially in the region weekly. The sterile insect technique involves releasing sterilized males that mate with wild females, preventing reproduction and causing population collapse. The USDA states it will release 100 million sterile insects per week in Mexico and along the U.S.-Mexico border.
FDA approves drugs to treat screwworm in dogs
The Food and Drug Administration recently approved the use of several drugs intended to treat dogs for New World screwworm infections, expanding treatment options beyond livestock.
USDA deploys 8,000 fly traps along U.S.-Mexico border
The USDA installed 8,000 fly traps along the U.S.-Mexico border to detect and monitor screwworm fly populations. The agency tested over 58,000 fly samples and 19,000 wild animal samples as part of surveillance efforts.
Screwworm cases detected in Mexico near Texas border
As of late May 2026, screwworm cases were confirmed in Mexico as close as 25 miles from the U.S. border, including a case in a five-year-old goat in Coahuila. Another case was found in a calf just 39 miles from the border, also in Coahuila, demonstrating the rapid northward progression of the parasite.
Screwworm outbreak in Florida Keys contained in 2016
An outbreak of New World screwworm affected wild deer populations in the Florida Keys in September 2016. Officials contained the outbreak by early 2017 without further spread beyond the initial area.
Economic losses from screwworm eradication estimated at $2.1 billion in Texas
Texas A&M University estimates that potential financial losses to Texas cattle producers and the hunting/wildlife industry from screwworm spread could conservatively reach $2.1 billion. The USDA estimates that keeping screwworms out of the U.S. saves the livestock industry approximately $900 million annually.
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2 alternative perspectives
First U.S. human screwworm case confirmed as food safety officials reassure public
First U.S. human screwworm case confirmed; food supply declared safe by federal authorities.
U.S. closes livestock ports to Mexico over screwworm threat
U.S. closes Mexican livestock ports to prevent screwworm outbreak spread.
USDA Expands Sterile Insect Releases as Screwworm Containment Intensifies
USDA escalates screwworm containment with expanded quarantine zone and accelerated sterile insect releases.
Texas declares disaster as screwworm eradication costs reach $2.1 billion
Texas declares disaster as screwworm eradication costs reach $2.1 billion.
Human screwworm infection confirmed as FDA approves canine treatments
Human screwworm case detected; FDA approves dog treatments as outbreak spreads.
USDA launches coordinated federal response to contain screwworm threat
USDA implements quarantine zones, border traps, and sterile insect breeding to eradicate detected screwworms.
Screwworm detected in Texas as outbreak escalates northward
Screwworm detected in Texas and Mexico after Panama barrier breach in 2022.