A New Risk to U.S. Cattle: The Screwworm Returns
A parasite once thought eradicated is making a quiet but alarming comeback.
The New World screwworm—a flesh-eating fly whose larvae burrow into open wounds of warm-blooded animals—is spreading north from Mexico and now threatens cattle herds in southern Texas. In severe infestations, it can kill animals outright.
According to the USDA, screwworms are "one of the most destructive parasites of livestock known to man." Eradicated from the U.S. in the 1980s, the parasite is now back on the radar, prompting emergency actions by state and federal officials.
What's Being Done
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The U.S. has suspended cattle imports from Mexico.
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Millions of sterile flies are being released across the southern border in an attempt to interrupt breeding cycles.
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The USDA is fast-tracking construction of a new sterile fly production facility in Texas.
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Ranchers are being told to monitor wounds, maintain detailed records, and report suspicious infections immediately.
“This is not just a livestock issue—it’s a threat to national food security.”
— USDA Screwworm Program Specialist
Why It Could Affect Beef Prices
While this outbreak hasn’t yet reached full crisis levels, experts warn it could:
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Further strain the U.S. beef supply chain, already under pressure from drought and declining herd sizes
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Drive up cattle treatment and containment costs
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Contribute to market volatility, particularly in southern states
Historically, the last major outbreak in the 1970s cost the U.S. cattle industry hundreds of millions of dollars—adjusted for inflation, over $1.8 billion in today’s economy.
What It Reminds Us About the Food System
Events like this expose just how fragile our food systems really are. Whether it’s a pandemic, inflation, a cyberattack, or—in this case—a parasitic fly, the centralized meat supply chain is vulnerable.
This is where local and regional producers come in. Smaller-scale farms operating outside industrial infrastructure are more agile, more transparent, and often more resilient when systems come under stress.
If nothing else, the screwworm news is a reminder that knowing where your food comes from—and how it's raised—isn’t just about values. It’s about security and preparedness.
P.S.
Are you curious how millions of "sterile flies" being released in affected areas is helping? Its actually quite amazing. Check out this video for more on the science of it.