Yesterday, I had the opportunity of attending a 2.5-hour training session presented by Texas AgriLife Extension on a very real and very alarming threat to Texas: the New World Screwworm (NWS). As the owner of Witten Pest Control and a lifelong advocate for animal rescue, the information I received was both scientifically fascinating and emotionally disturbing.
This isn’t just another pest to watch—it’s a potential crisis quietly moving closer.
What Is the New World Screwworm?
The New World Screwworm is not your average fly. Unlike typical pests, it infests live, warm-blooded animals—not decaying tissue. The female fly lays eggs on open wounds, mucous membranes, or broken skin of animals including cattle, wildlife, working dogs, pets, and even humans.
A single fly lays 200–300 eggs, which hatch in 5–6 hours. The larvae burrow into living flesh and can kill a host within a week.
Common sites of infestation:
Nostrils, mouth, and eyes
Anus and genital area
Flea/tick bites and open sores
Surgical wounds (spay/neuter sites)
Umbilical cords of newborn animals
This means any minor injury can become a death sentence for an animal—especially for strays, feral animals, and wildlife, which often go unnoticed and untreated.
How Close Is the Threat?
As of today, confirmed fly sightings are just 700 miles from the Texas border, in southern Mexico. These flies can travel up to 12 miles in a single day to find a host. It’s no longer a matter of if they reach Texas—it’s how fast, and how ready we are to respond and prevent them from reaching Texas.
In November 2024, the U.S. closed the border to cattle imports from Mexico due to rising NWS cases in livestock. That closure remains in place today, and the pressure is mounting.
What’s Being Done? Science in Action: SIT (Sterile Insect Technique)
There is hope. One of the most impressive tools in the fight against NWS is the Sterile Insect Technique (SIT):
New World Screwworm flies are sterilized using Cobalt-60 radiation.
Over 100 million sterile flies are now being released regularly in Mexico.
Since female flies only mate once, the goal is that most will mate with sterile males, halting reproduction and shrinking the population.
This effort, combined with Integrated Pest Management (IPM)—including monitoring, surveillance, and inspection—is our best defense right now.
A Look Back: Screwworm in History
The New World Screwworm isn’t new—it’s ancient and deadly. Here’s a historical timeline:
1500s: Documented by Spanish colonizers; death in humans via slave-branding wounds.
1700s: Infested livestock in Spanish missions.
1842: Detected in the U.S. Southwest.
1964: Eradicated in Texas.
1987: Reintroduced via imported dogs.
2023: Renewed outreach and detection programs launched.
2025: U.S.-Mexico cattle border still closed.
Without immediate action, we risk repeating this history—on a much larger scale.
Why I’m Sharing This
As a pest control professional, this is highly relevant to our field. But as someone who’s spent 35 years in dog rescue across Texas, it’s personal.
The growing number of homeless, feral, and stray animals in our cities and rural areas are at extreme risk. These animals often have untreated injuries, are malnourished, or recovering from surgeries. Even the most loved house pets can be at risk through something as simple as a scratch, flea bite, or recent spay/neuter.
I can’t ignore this. And I won’t.
What You Can Do: Every Report Matters
This is a community-wide issue, and we all have a role to play. Here's how you can help protect Texas:
- Check pets and livestock daily for wounds or odd larvae
- Report any suspicious fly or maggot activity on animals
- Contact your veterinarian IMMEDIATELY
- Report cases to the Texas Animal Health Commission (Beeville Region)
- 361-358-3234
- Or contact your local AgriLife Extension office
Even if testing turns out to be a false alarm, authorities want to know. Early reporting saves lives—and livelihoods.
Final Thoughts
The New World Screwworm is more than a pest—it's a potential public health and animal welfare disaster. As Texans, we need to rally around this issue and help be the early warning system our state depends on.
Together, we can protect:
Our cattle industry
Our wildlife
Our working animals and family pets
Our feral dog and cat populations
Ourselves and our neighbors
If you see something, say something. Call your vet, report concerns, and share this post. Let’s stay ahead of this threat—for the animals we love and the industries we rely on.
Thank you for reading and for caring.
Patti Witten
Owner, Witten Pest Control
Serving Residential & Commercial Customers Since 1948
Advocate for Animal Rescue and Responsible Pest Control