• Home
  • Latest
  • Fortune 500
  • Finance
  • Tech
  • Leadership
  • Lifestyle
  • Rankings
  • Multimedia

Trendingnow

1

Ohio city workers are covering automated license plate readers with trash bags as officials sound the alarm on 'egregious violations' of privacy

2

10,000 Boomers a day, $39 trillion in debt, and no benefit cuts: Bessent stakes Social Security on the Trump economy

3

A single new sentence in SpaceX's amended IPO filing could signal the biggest merger in history

1

Ohio city workers are covering automated license plate readers with trash bags as officials sound the alarm on 'egregious violations' of privacy

2

10,000 Boomers a day, $39 trillion in debt, and no benefit cuts: Bessent stakes Social Security on the Trump economy

3

A single new sentence in SpaceX's amended IPO filing could signal the biggest merger in history
EnvironmentFood and drink

A flesh-eating fly just crossed into Texas. The last time it did, it took 30 years to stop

By
John Hanna
John Hanna
,
Russ Bynum
Russ Bynum
, and
The Associated Press
The Associated Press
Down Arrow Button Icon
By
John Hanna
John Hanna
,
Russ Bynum
Russ Bynum
, and
The Associated Press
The Associated Press
Down Arrow Button Icon
June 5, 2026, 12:02 PM ET

The New World screwworm fly is threatening the $113 billion U.S. cattle industry for the first time in more than a half century, with an infestation from its flesh-eating larvae confirmed in south Texas.

Recommended Video

The infestation was discovered in a single 3-week-old calf in La Pryor, Texas, about 100 miles (161 kilometers) southwest of San Antonio and 50 miles (80 kilometers) from the U.S.-Mexico border. Federal and state officials had been working to keep the parasite from reaching Texas, home to $17 billion worth of the nation’s cattle, making it the industry’s No. 1 state.

The deadly flies were detected in Mexico late in 2024, after years of being contained at the southern end of Panama.

The fly was an annual warm-weather scourge of cattle ranchers from at least the 1930s through the 1960s, until the U.S. eradicated the pest by breeding sterile male flies and dropping swarms of them from planes to mate with wild females. The USDA said the most recent case was the first in Texas since 1966.

Here is what to know about the fly, the threat it poses and the response:

Being unusual makes the flies a threat

The New World screwworm fly in the Western Hemisphere and its Old World cousin in Africa and Asia are unusual among flies because their larvae, or maggots, eat live flesh and fluids instead of dead material. Females lay their eggs in open wounds and mucous membranes after mating only once in their monthslong lives.

Any warm-blooded animal, including wildlife, pets and occasionally even humans, can be infested.

Livestock are vulnerable because of how they’re handled, Lee Haines, an associate research professor of biological sciences at the University of Notre Dame, said in an email Thursday. Standard practices with cattle can break the skin, including shearing and de-horning, or even moving them in and out of corrals can cause scrapes and cuts. Birth would also make a mother and calf vulnerable, she said.

Stephen Diebel, a Texas rancher and president of the Texas & Southwestern Cattle Raisers Association, added that even wounds “as small as a tick bite,” can put cattle at risk.

Death can result if an infestation is not treated, though a dozen treatments have been approved for use in a variety of species. In decades past, ranchers had tens of millions of dollars in losses — potentially billions in today’s dollars.

But agriculture officials were quick to note that the fly does not infest food, and U.S. Agriculture Secretary Brooke Rollins said it’s unlikely to damage beef production — welcome news given that consumers are already facing record prices.

Officials sounded alarms for nearly 2 years

Federal and state officials and cattle industry leaders have been sounding public alarms about the fly’s movement through Mexico and toward the U.S. since a case was confirmed in southern Mexico in November 2024.

Officials had considered the pest eradicated from Central and North America nearly two decades before an outbreak in Panana prompted a state of emergency there early in 2023, according to the joint U.S.-Panama program established in 1994 to stop the parasite. Cases jumped to Costa Rica and Nicaragua later that year.

Edward Burgess, a University of Florida entomologist who studies the fly, said it reproduces quickly and is carried across wide areas by its hosts, namely wild animals such as deer. Outside of Panama, he said, programs that produced and released sterile flies have largely shut down.

“It’s hard to stay ahead of it because of how fast that fly is able to move and regenerate,” Burgess said.

Outside the US, thousands of animals and hundreds of humans sickened

As of June 2, the parasite had sickened more than 171,700 animals and 2,000 people across Central America and Mexico, according to the U.S. Centers for Disease Control and Prevention. There have been 10 human deaths, the CDC says.

Starting in May 2025, Rollins closed border entries to livestock and on Thursday she credited that move with delaying the fly’s arrival in Texas by a year.

Rollins has argued that the Mexican government has not done enough to control animals moving within the country, a suggestion Mexican authorities have rejected.

But Haines said climate change is a key element in the spread of a tropical species that thrives in warm weather. Warmer temperatures are expanding the fly’s habitat and cold snaps that killed them off each year in marginal habitats are becoming less frequent and less severe, she said.

Officials quarantine a swath of Texas

Texas State Veterinarian Bud Dinges imposed a 12-mile (20-kilometer) quarantine zone covering much of Zavala County, home to La Pryor, and a small part of neighboring Uvalde County. Animals cannot leave that zone without being inspected.

Local ranchers are concerned that the fly will spread among wildlife, particularly deer, as a small, short-lived outbreak did in the Florida Keys in 2016. That was the last time a U.S. case was confirmed among animals, though the CDC confirmed a case last year in a Maryland man who had traveled to El Salvador and recovered.

Zavalas County Sheriff Eusevio Salinas said Thursday that state officials were setting up several road checkpoints in the county to enforce the quarantine.

“They said they were going to do that for three to four days, and hopefully after that it’s already under control,” Salinas said.

In Texas, shots and fly drops

Diebel, whose family ranch is about 200 miles (322 kilometers) east of the quarantine zone, said ranchers are proactively giving injections that prevent screwworm infestation. They’re also taking extra care to treat wounds from ear tagging and other practices and keeping a close eye for signs of illness.

The USDA has been dropping sterile flies in south Texas since February, when it opened a center for dispersing them in south Texas. It is now dropping them twice a week, for a total of 4 million flies, and it’s also putting 4 million more a week in the ground as pupae, flies in the stage between larvae and adult, said Rear Admiral Michael Schmoyer, a member of the USDA’s response team.

Releasing sterile files is both time-tested and highly effective. While males are “promiscuous,” in the scientific sense, females are not, and if their one mating hookup is with a sterile male, no eggs from that female will hatch.

Once sterile males are prevalent enough, the fly’s population declines and then dies out.

But with sites outside Panama shut down for years, the USDA didn’t think sterile flies were being bred fast enough. It invested $21 million in a new fly-breeding facility in southern Mexico that is expected to start operations next month.

The USDA also is spending $750 million to build a fly factory in southern Texas that can produce up to 300 million sterile flies a week. It is expected to begin operating next fall.

Subscribe to Fortune Gulf Brief. Every Tuesday, this new newsletter delivers clear-eyed, authoritative intelligence on the deals, decisions, policies, and power shifts shaping one of the world’s most consequential regions, written for the people who need to act on it. Sign up here.
About the Authors
By John Hanna
See full bioRight Arrow Button Icon
By Russ Bynum
See full bioRight Arrow Button Icon
By The Associated Press
See full bioRight Arrow Button Icon

Latest in Environment

Finance
Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam
By Fortune Editors
October 20, 2025
Finance
Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam
By Fortune Editors
October 20, 2025
Finance
Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam
By Fortune Editors
October 20, 2025
Finance
Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam
By Fortune Editors
October 20, 2025
Finance
Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam
By Fortune Editors
October 20, 2025
Finance
Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam
By Fortune Editors
October 20, 2025

Most Popular

Finance
Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam
By Fortune Editors
October 20, 2025
Finance
Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam
By Fortune Editors
October 20, 2025
Finance
Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam
By Fortune Editors
October 20, 2025
Finance
Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam
By Fortune Editors
October 20, 2025
Finance
Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam
By Fortune Editors
October 20, 2025
Finance
Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam
By Fortune Editors
October 20, 2025
Fortune Secondary Logo
Rankings
  • 100 Best Companies
  • Fortune 500
  • Global 500
  • Fortune 500 Europe
  • Most Powerful Women
  • World's Most Admired Companies
  • See All Rankings
  • Lists Calendar
Sections
  • Finance
  • Fortune Crypto
  • Features
  • Leadership
  • Health
  • Commentary
  • Success
  • Retail
  • Mpw
  • Tech
  • Lifestyle
  • CEO Initiative
  • Asia
  • Politics
  • Conferences
  • Europe
  • Newsletters
  • Personal Finance
  • Environment
  • Magazine
  • Education
Customer Support
  • Frequently Asked Questions
  • Customer Service Portal
  • Privacy Policy
  • Terms Of Use
  • Single Issues For Purchase
  • International Print
Commercial Services
  • Advertising
  • Fortune Brand Studio
  • Fortune Analytics
  • Fortune Conferences
  • Business Development
  • Group Subscriptions
About Us
  • About Us
  • Press Center
  • Work At Fortune
  • Terms And Conditions
  • Site Map
  • About Us
  • Press Center
  • Work At Fortune
  • Terms And Conditions
  • Site Map
  • Facebook icon
  • Twitter icon
  • LinkedIn icon
  • Instagram icon
  • Pinterest icon

Latest in Environment

evers
LawWisconsin
Wisconsin governor hails ‘historic’ $10m settlement over forever chemicals but a mayor sees ‘drop in the bucket’
By Scott Bauer and The Associated PressJune 5, 2026
40 minutes ago
fish
Environmentfishing
DeSantis promised anglers a ‘God-given right to fish.’ It ran into a 25% kill rate and a Washington injunction
By Joshua Goodman, Helen Wieffering, Shelby Lum and The Associated PressJune 5, 2026
53 minutes ago
A flesh-eating fly just crossed into Texas. The last time it did, it took 30 years to stop
EnvironmentFood and drink
A flesh-eating fly just crossed into Texas. The last time it did, it took 30 years to stop
By John Hanna, Russ Bynum and The Associated PressJune 5, 2026
60 minutes ago
A man in a crowd holds a sign that says, "Moratorium NOW!"
EnvironmentData centers
‘Big Tech is desperate’: Amazon engineers are calling out the tech giant for its $200 billion in data center spending after slashing 30,000 workers
By Sasha RogelbergJune 5, 2026
9 hours ago
The death of the billboard: Amsterdam’s ad crackdown is part of a much bigger European shift 
EnvironmentAdvertising
The death of the billboard: Amsterdam’s ad crackdown is part of a much bigger European shift 
By Sam BirchallJune 5, 2026
9 hours ago
gg
Environmentprotests
Albanian protesters are furious about a giant development on a virgin beach that Jared Kushner and Ivanka Trump discovered on vacation
By Zana Cimili and The Associated PressJune 4, 2026
1 day ago

Most Popular

Ohio city workers are covering automated license plate readers with trash bags as officials sound the alarm on 'egregious violations' of privacy
Cybersecurity
Ohio city workers are covering automated license plate readers with trash bags as officials sound the alarm on 'egregious violations' of privacy
By Sasha RogelbergJune 3, 2026
2 days ago
10,000 Boomers a day, $39 trillion in debt, and no benefit cuts: Bessent stakes Social Security on the Trump economy
Economy
10,000 Boomers a day, $39 trillion in debt, and no benefit cuts: Bessent stakes Social Security on the Trump economy
By Nick LichtenbergJune 4, 2026
1 day ago
A single new sentence in SpaceX's amended IPO filing could signal the biggest merger in history
Startups & Venture
A single new sentence in SpaceX's amended IPO filing could signal the biggest merger in history
By Shawn TullyJune 4, 2026
1 day ago
CEO says anyone who works from home is grabbing groceries or at the vet 30% of the time—and shows off his busy office at Friday 5 p.m. to prove it
Success
CEO says anyone who works from home is grabbing groceries or at the vet 30% of the time—and shows off his busy office at Friday 5 p.m. to prove it
By Orianna Rosa RoyleJune 4, 2026
1 day ago
Current price of oil as of June 4, 2026
Personal Finance
Current price of oil as of June 4, 2026
By Joseph HostetlerJune 4, 2026
1 day ago
AI CEOs from OpenAI, Anthropic, and Microsoft set aside their rivalry to warn Congress AI is making it too easy to design and create bioweapons
AI
AI CEOs from OpenAI, Anthropic, and Microsoft set aside their rivalry to warn Congress AI is making it too easy to design and create bioweapons
By Marco Quiroz-GutierrezJune 5, 2026
9 hours ago

© 2026 Fortune Media IP Limited. All Rights Reserved. Use of this site constitutes acceptance of our Terms of Use and Privacy Policy | CA Notice at Collection and Privacy Notice | Do Not Sell/Share My Personal Information
FORTUNE is a trademark of Fortune Media IP Limited, registered in the U.S. and other countries. FORTUNE may receive compensation for some links to products and services on this website. Offers may be subject to change without notice.