If you've been on social media or read any horse industry news this week, you may have seen some alarming headlines about something called the New World Screwworm. And if you're like most horse owners, your first instinct was probably some version of: what is this, should I be panicking, and what do I do?
We're going to answer all three of those questions today — calmly and clearly — because that's what we're here for.
WHAT IS THE NEW WORLD SCREWWORM?
The New World Screwworm, or NWS, is a parasitic fly whose larvae feed on the living tissue of warm-blooded animals. That includes horses, cattle, wildlife, pets, and in rare cases, people. The female fly is attracted to open wounds, where she deposits her eggs.
When those eggs hatch, the larvae burrow into living flesh — not dead tissue, living tissue — and if left untreated, the infestation can be life-threatening. It sounds terrifying, and untreated cases absolutely can be. But here is the important context: this is not a new pest, and it is not one we don't know how to handle.
WE'VE BEATEN THIS BEFORE
The United States was afflicted with screwworm for much of the 20th century before a remarkably successful eradication campaign cleared it from the country entirely by the 1960s. The method used — called the sterile insect technique, which involves releasing sterilized male flies that mate with wild females but produce no offspring — is considered one of the most successful pest eradication efforts in agricultural history.
The screwworm was kept out of the United States for decades. It has periodically resurfaced — a 2016-2017 outbreak in the Florida Keys was successfully contained — and now it is back in the news again.
WHERE THINGS STAND RIGHT NOW
The situation has been developing since 2023, when outbreaks began spreading north through Central America and Mexico. By September 2025, a confirmed case was detected in Nuevo León, Mexico, less than 70 miles from the U.S.-Mexico border.
On June 3, 2026, the USDA confirmed New World Screwworm in a calf in Zavala County, Texas — the first confirmed U.S. case in this resurgence. Texas Governor Greg Abbott has since issued a state disaster declaration, allowing all state government resources to be directed toward prevention and potential eradication. There has been no confirmed case of horses in the United States. But officials are on high alert, and horse owners across the country — not just those in Texas — should be informed and paying attention.
SHOULD YOU BE WORRIED?
If you live in or near Texas, or plan to travel there with horses, you should be informed and vigilant. If you are elsewhere in the country, you do not need to panic, but you should know what to watch for.
The American Horse Council put it well: while this is alarming, we have dealt with this before and have full confidence in current science-based strategies. We've eliminated it before, and we'll do it again — but only if horse owners do their part to stay vigilant.
WHAT DOES THE SCREWWORM LOOK LIKE?
Knowing what you're looking for matters. Here's how to identify the fly and the larvae:
The adult screwworm fly is slightly larger than a common housefly, with distinctive orange eyes, a metallic blue or green body, and three dark stripes along its back. The larvae have a cylindrical shape that tapers to a pointed head and widens at the rear, with rings of dark spines around their bodies that help them burrow into tissue.
This distinguishes them from common maggots, which are typically white or pale yellow and have a more uniform shape without the distinctive spines.
SIGNS YOUR HORSE MAY BE INFESTED
Watch for any of the following:
A wound that worsens quickly or fails to heal normally. An unusual or foul smell coming from a wound. Visible larvae or maggots in or around a wound. Excessive irritation, restlessness, or discomfort that seems focused on a wound area. Drainage or enlarging wounds that don't respond to normal treatment.
If you notice any of these signs, contact your veterinarian immediately. Do not attempt to treat a suspected screwworm infestation on your own. This is a situation that requires professional evaluation, and your veterinarian will coordinate with state and federal animal health officials on proper testing and treatment.
WHAT YOU CAN DO RIGHT NOW TO PROTECT YOUR HORSE
The good news is that prevention is straightforward, and most of it is just good horse ownership practiced consistently.
Check your horse daily for any wounds, drainage, foul odor, or unusual irritation. Even minor cuts deserve attention right now. The screwworm fly is attracted to open wounds, so the faster you find and treat a wound, the smaller the window of opportunity for the fly.
Clean and protect wounds immediately. Treat even small cuts promptly. Keep wounds covered where possible and monitor them closely until they are fully healed.
Maintain consistent fly control. Good stable hygiene and regular fly control practices reduce the overall fly population around your horses and lower the risk of exposure.
Be especially careful after procedures. Activities like castration that create open wounds increase susceptibility. If your horse is recovering from any kind of surgery or procedure right now, monitor the wound site closely and keep it clean and treated.
Be aware of where you're traveling. If you are hauling horses to or through Texas or near the southern border, stay informed about current conditions and check with your state veterinarian for any movement restrictions or requirements. Horse shows and events in affected areas may require veterinary certificates or antiparasitic treatment as a condition of entry.
Do not move horses from affected areas without guidance from state officials. Movement of animals is one of the primary ways this pest spreads, and following state guidelines for animal movement is one of the most important things individual horse owners can do right now.
TREATMENT OPTIONS
The FDA has issued several Emergency Use Authorizations for treatments in response to this outbreak, including topical powders, ointments, and injectable options. Your veterinarian will be the right person to guide you on what is appropriate for your horse's specific situation if an infestation is suspected.
Do not attempt to self-treat a suspected screwworm infestation without veterinary guidance.
THE BOTTOM LINE
This is a serious situation that deserves serious attention. It is not, however, a reason to panic. The United States has eradicated this pest before, and the tools and strategies to do it again are already in motion. The USDA has surveillance traps deployed across Texas, Arizona, and New Mexico. Sterile fly releases are underway. State and federal officials are coordinating responses.
Your job as a horse owner is to stay informed, stay vigilant, and take the simple daily steps that give your horse the best protection available right now. Check for wounds. Keep things clean. Know what to watch for. Call your vet if something doesn't look right.
That's not complicated. That's just good horse ownership — and your horse is lucky to have someone paying attention.
We will continue to share updates as this situation develops.
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SOURCES & FURTHER READING
We want you to be able to verify everything we've said here and read more if you'd like. Here are the sources we used:
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U.S. Department of Agriculture (USDA) — Animal and Plant Health Inspection Service (APHIS) Official screwworm response and prevention information https://www.aphis.usda.gov/livestock-poultry-disease/cattle/ticks/screwworm
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Screwworm.gov — Unified Government Response https://www.aphis.usda.gov/animals/animal-health/livestock-and-poultry-disease/stop-screwworm
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American Horse Council — Screwworm Information for Horse Owners https://horsecouncil.org/screwworm/
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U.S. Equestrian Federation (USEF) — Alert: Screwworm Confirmed in the United States https://www.usef.org/media/newsletter/the-insider/alert-screwworm-confirmed-in-united-states
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U.S. Equestrian Federation (USEF) — As Screwworm Moves Closer to the United States, Horse Community Should Be on the Lookout https://www.usef.org/media/press-releases/alert-as-screwworm-moves-closer-to-united
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FDA — Animal Drugs for New World Screwworm (Emergency Use Authorizations) https://www.fda.gov/animal-veterinary/safety-health/animal-drugs-new-world-screwworm
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dvm360 — New World Screwworm Confirmed in United States https://www.dvm360.com/view/new-world-screwworm-confirmed-in-united-states-usda-announces
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Texas Governor's Office — Governor Abbott Issues New World Screwworm Disaster Proclamation https://gov.texas.gov/news/post/governor-abbott-issues-new-world-screwworm-disaster-proclamation-in-june-2026
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American Society for Microbiology — New World Screwworm: Rise, Fall and Resurgence https://asm.org/articles/2025/september/new-word-screwworm-rise-fall-resurgence
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Mid-South Horse Review — New World Screwworms Edge Closer to U.S. https://midsouthhorsereview.com/new-world-screwworms-edge-closer-to-us-threatening-horses-and-livestock-health
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DISCLAIMER: The information in this email is intended for general informational purposes only and should not be substituted for professional veterinary or agricultural advice. We are not veterinarians or animal health officials. We are horse people who care deeply about your animals and wanted to share what we've learned from the most credible sources available at the time of writing. This situation is actively developing, and details may change. We have done our best to source accurate, up-to-date information, but we always encourage you to consult your veterinarian and check with your state animal health officials for the most current guidance specific to your location and situation.