Can Horses Get Screwworm? What Texas Horse Owners Need to Know About New World Screwworm?
Last winter, it was the EHV outbreak. This summer, it's a fly that lays flesh-eating larvae. Texas horse owners can't seem to catch a break.
The New World screwworm has been confirmed in Texas for the first time in decades, and Governor Abbott has expanded a statewide disaster declaration in response, directing all state agencies to be ready to act. That alone tells you how seriously Texas is treating this. Here at Cashel Company, we are horse owners ourselves and understand the growing concern many horse owners are feeling right now as developments surrounding the New World screwworm continue.
While much of the early coverage has focused on cattle, many Texas horse owners are asking the same question: Can horses get screwworm? How at risk are we? If you own horses, here's what you need to know and what you can do to stay ahead of it.
For the latest case counts and official updates, USDA APHIS maintains a New World Screwworm announcement page, and the federal government's central hub for ongoing information is screwworm.gov.
What Is New World Screwworm?
The New World screwworm is a parasitic fly roughly the size of a house fly, with a gruesome habit. Unlike ordinary maggots that feed on dead tissue, screwworm larvae burrow into the living flesh of warm-blooded animals.
● Adult flies lay eggs in open wounds or body openings (nose, eyes, etc.)
● The eggs hatch into larvae (maggots)
● Those larvae start feeding on living tissue, screwing deeper into the wound as they go (hence the name)
● Left untreated, infestations can cause serious tissue damage and even death
This pest was eradicated from the United States decades ago through the Sterile Insect Technique, and agricultural officials are now using that same approach in active response to the current outbreak — USDA has been releasing millions of sterile male flies over the affected areas to disrupt the reproductive cycle, with releases happening multiple times a week by both air and ground. Recent reports of New World screwworm in Texas have prompted animal health officials to intensify monitoring and encourage livestock owners to inspect their animals regularly.
What Is Sterile Insect Technique?
The Sterile Insect Technique, as explained by USDA APHIS, was developed in the 1950s and is a proven method for eradicating the NWS population — in fact, it's how the U.S. wiped out screwworm the first time around. Pupae are exposed to gamma radiation to produce sterile male flies, which are then released in large numbers to mate with wild females. Because female screwworms typically mate only once, those females lay unfertilized eggs, and the population steadily collapses over time. This is the same approach USDA is actively deploying right now in the affected Texas counties, with sterile fly releases ongoing by both air and ground as part of the current eradication effort.
Can Horses Get Screwworm?
Yes. Horses, along with cattle, sheep, goats, dogs, cats, and other warm-blooded animals, can all be affected. Animal health officials have been clear that screwworm doesn't discriminate by species.
The greatest risk comes from open wounds and untreated injuries. As horse owners, we know how easily our horses can get into trouble on a daily basis. These include fence scrapes, bite marks from playing in the pasture, hoof and leg injuries, castration or surgical sites, and sensitive areas like the sheath and the corners of the eyes, as well as any break in the skin. Anywhere a fly can reach raw tissue is a potential target.
A Special Note for Foals, Colts, and Broodmares
If you have a mare due to foal, a foal freshly hitting the ground, or a colt due for a castration, this is worth extra attention. Confirmed cases so far have included young animals with screwworm larvae found in the umbilical area. This is a reminder that foals and calves are uniquely vulnerable. For horse owners, that risk translates directly: a foal's umbilical stump, any tearing or wounds a mare sustains during foaling, and even a colt's fresh castration site are all exactly the kind of raw, healing tissue screwworm flies are drawn to.
If you're foaling out mares this season, treat navel care and post-foaling checks as part of your screwworm prevention plan. Dip or treat the umbilical stump promptly, keep a close eye on it as it dries and heals, and don't overlook the mare herself in the days after foaling. The same goes for colts recovering from castration. A few extra minutes of inspection during an already busy, exhausting time can catch a problem before it becomes a serious one.
What Signs Should Horse Owners Watch For?
Understanding potential screwworm symptoms in horses can help owners identify problems early and seek veterinary care before an infestation worsens.
● Wounds that won't heal or seem to be getting worse
● Unusual or bloody drainage
● A strong, foul odor coming from a wound
● Irritation, restlessness, or discomfort around a cut or abrasion
● Persistent head-shaking, rubbing, or worrying at one specific spot
● Irritation, restlessness, or discomfort around a cut or abrasion
● Persistent head-shaking, rubbing, or worrying at one specific spot
● Heavy fly activity concentrated around an injury
One of the most reliable warning signs is smell. A distinct, foul odor from a wound is a red flag. If you suspect screwworm, contact your veterinarian right away.
Check Your Horses Every Day
The single most repeated piece of advice from animal health officials and veterinarians is also the simplest: look at your livestock and horses every day.
Daily, hands-on inspection lets you catch a small wound before it becomes an open door for flies to lay eggs. For us horse owners, that means checking legs, the belly and cinch area, the face, ears, and eyes, and any spot where tack sits, or skin has been broken. Even something as small as a tick bite can become a target for NWS. It is important to remove your horse's fly protection and inspect underneath it every day.
Fly Control Is More Important Than Ever Before
Because screwworm flies target open wounds and raw tissue, keeping flies away from your horse — especially from any cut, scrape, or sensitive area — is another layer of protection this summer. While no product can guarantee prevention of screwworm, effective fly protection for horses can help reduce irritation and limit fly pressure around vulnerable areas.
● Horse fly masks help shield the eyes, ears, and face, sensitive areas flies are often drawn to.
● Fly sheets for horses help reduce overall fly pressure across the body.
● Fly boots protect the legs, where cuts and scrapes are common.
A strong fly-management program helps limit irritation and keeps flies away from vulnerable spots during peak fly season.
Stay Proactive This Summer
The good news is that horse owners aren't powerless. For Texas horse owners, the best defense against screwworm is just best animal care practice: doctor wounds early, check your horses, animals, and livestock every day, and be proactive with your horse fly protection.
Always remember that you are your horse's best advocate, and it's your responsibility to look out for them.
To shop the full line of horse fly protection at Cashel, head to:
https://cashelcompany.com/collections/fly-protection
If you live in Texas and suspect screwworm in any animal, report it immediately. Anyone can report a suspected case, not just veterinarians:
● Livestock: Contact the Texas Animal Health Commission (TAHC) at 1-800-550-8242, or find your closest TAHC region office.
● Wildlife: Contact the Texas Parks and Wildlife Department (TPWD).
● General updates and resources: screwworm.gov
Disclaimer: This article is for informational purposes only and is not intended to replace veterinary advice. If you suspect screwworm or any other health issue in your horse, contact your veterinarian immediately.
About Cashel Company: Since 1993, Cashel has pursued a simple mission: to make life safer, easier, and more enjoyable for horses and the people who love them. What began with a commitment to creating products horse owners could trust has grown into a comprehensive collection of dependable solutions for horse, rider, and barn. Over the years, Cashel has become known for innovation, practical problem-solving, and products that simply work. From fly protection and trailering gear to tack, barn essentials, and rider accessories, every product is designed with one goal in mind: helping horse owners care for their horses with confidence. We understand that horses don't care what discipline you ride, what breed they are, or whether you're chasing a championship or spending an evening at home in the barn.