New World screwworm has returned to Texas and the broader Southwest after decades away, and confirmed cases now include pets, not just livestock. This parasite is a fly whose larvae burrow into living tissue through any open wound, and an unnoticed infestation can turn a small scrape into a serious, fast-worsening injury. The good news is that a screwworm case caught early is very treatable, and there are practical steps you can take at home to keep your dog or cat from becoming a target in the first place. The problem is that most families in the region have never had to think about this parasite, so the wound in the backyard looks like nothing until it isn’t.
Fort Worth sits squarely in the region where screwworm has resurfaced, and Animal Hospital Southwest is watching wounds a little more carefully than we did a year ago. Our team has the in-house lab to work up an infested wound, clean and debride it properly, and get your pet started on treatment right away, and a regular wellness and preventative visit is a great time to talk through the small habit changes that lower your pet’s risk. If you have spotted a suspicious wound, or you just want to get ahead, book an appointment with us. If the wound is actively worsening or you can see larvae, call ahead and come straight in during our open hours, and head to the nearest veterinary ER if it is after hours.
Quick Facts
- New World screwworm is a fly whose larvae feed on living tissue, so an ordinary-looking scrape can become a deep, worsening wound if a fly lays eggs in it.
- The United States wiped this parasite out decades ago, which is exactly why its return to Texas and the Southwest is such a big deal and worth your attention now.
- Caught early, a screwworm case is very treatable with professional wound care and larvae removal, so a fast trip to the vet makes an enormous difference in the outcome.
- Daily wound checks, prompt care of any cut or scrape, and staying current on your pet’s year-round parasite prevention are your best defenses, and they work for indoor and outdoor pets alike.
What Is New World Screwworm, and Why Does It Feed on Living Flesh?
New World screwworm is the larval stage of a parasitic fly, Cochliomyia hominivorax. Unlike the everyday maggots you might picture, which clean up only dead, rotting tissue, screwworm larvae go the other way and burrow into and feed on living flesh. That is exactly what sets this parasite apart.
The life cycle is simple and, honestly, a little grim to picture. An adult female fly, drawn to the smell of a wound, lays a cluster of eggs at the edge of any break in the skin. Those eggs hatch into larvae within a day, and the larvae immediately start tunneling into the surrounding living tissue, screwing themselves deeper as they feed (which is exactly where the name comes from). After several days they drop to the ground, pupate, and emerge as new flies ready to find the next wound. It is a fast loop, and it does not care whose wound it finds. Screwworm can affect livestock, wildlife, dogs, cats, and occasionally people. If your dog has ever come home from a romp with a torn ear or a split pad, you already know how ordinary the doorway can be.
Why Is Screwworm Such a Serious Threat, Not Just a Bad Case of Flies?
Screwworm is dangerous because the larvae eat living tissue, which means the wound gets bigger and deeper on its own, drawing in more flies and more eggs in a cycle that can spiral over just a few days. This is not the fly strike you might have heard about on a farm, where maggots clean up dead tissue on a sick animal. This is active destruction of healthy flesh.
The stakes go well beyond one uncomfortable pet. Left untreated, an infestation causes real suffering, can become life-threatening, and historically devastated cattle herds across the South, which is why the country spent enormous effort getting rid of it. The screwworm eradication effort pushed this parasite out of the country decades ago, so a case here today is a genuine reversal, not a routine fly problem. That eradication used a clever trick called the sterile insect technique, releasing millions of sterile male flies so wild females mated but produced no offspring, and it worked so well that a couple of generations of Texas pet families simply never had to think about this. That is the part worth sitting with. The reason a backyard scrape looks like nothing is that, until recently, it usually was.
How Did Screwworm Cross the Border Into the Southwest?
Screwworm has been working its way north from Central America, up through Mexico and into the United States, which puts Texas and the rest of the Southwest on the leading edge. Because the spread keeps shifting, the smartest move for a Fort Worth family is to check current, official case counts.
That count lives with the official record of confirmed cases in the United States, not in any figure that was true a month ago. It is worth knowing that the response has been aggressive: the USDA is releasing sterile flies along the southern border and into Mexico, the same technique that wiped screwworm out the first time, and monitoring wildlife in high-risk Texas counties. None of this means every dog in the neighborhood is about to be infested. It means the risk is no longer zero, and awareness is cheap insurance.
What Are the Signs of a Screwworm Infestation?
A screwworm wound looks and behaves differently from a normal healing scrape: it grows instead of shrinking, often smells foul, may show visible larvae or bloody discharge, and clearly bothers your pet. Because the larvae feed inward, what starts as a small opening can turn into a surprisingly deep pocket in the tissue over just a day or two.
Here is what to watch for:
- A wound that is getting worse, not better: Healing wounds shrink and dry over time; a screwworm wound widens and deepens.
- Visible larvae: You may see small, pale, wriggling maggots packed into the wound, sometimes tail-end up.
- A strong, foul odor: Infested wounds often smell distinctly bad, which is frequently what tips a family off.
- Discharge or bleeding: A bloody or serous ooze coming from the site is common.
- Signs of pain or distress: Licking, biting, restlessness, hiding, or crying out when the area is touched.
- Any break in the skin, plus natural openings: Cuts, bites, and surgical incisions are obvious targets, but the nose, ears, eyes, and other openings can be too.
Some patients are especially vulnerable: newborns with a healing navel, pets recovering from a recent surgery, and any animal with a fresh, treated wound. If something looks off, do not wait it out. You can reach us the same day during our open hours, and the sooner we see the wound, the better.
How Is Screwworm Diagnosed and Reported?
Diagnosing screwworm starts with a careful look at the wound, examination of any larvae present, and confirmation of the species, because screwworm is a reportable pest that must be flagged to animal health authorities the moment it is suspected. Fast reporting is what keeps one infestation from becoming many. This is not a wait-and-see situation, and it is not something to manage with home remedies from the internet.
When you come in, our team examines the wound, collects larvae for identification, and uses tools like digital radiography and in-house diagnostics to see how deep the damage goes and rule out complications. If you suspect screwworm, call us right away and come straight in.
How Is Screwworm Treated in Dogs and Cats?
Treatment centers on professional wound care: thoroughly cleaning and debriding the wound, carefully removing every larva, applying approved products to kill any that remain, and providing supportive care like pain control and antibiotics for secondary infection. Done properly and early, the prognosis is genuinely good, which is the reassuring part of an otherwise grim-sounding parasite.
Treatment for screwworm in dogs and cats combines professional wound cleaning, careful larvae removal, approved products, and supportive care, and pets caught early tend to do well. The reason this belongs in a veterinary setting rather than the bathroom sink is depth. Larvae anchor themselves and burrow, so getting all of them out, confirming the wound is clean, and managing the tissue damage takes proper sedation, instruments, and follow-up. We also watch for reinfestation, since a healing wound is still an attractive target for the next fly. For pets that need it, we provide urgent and emergency care during our open hours, and after-hours emergencies should head straight to the nearest veterinary ER.
The medication side of screwworm care has changed fast, and it is genuinely reassuring. The isoxazoline class of parasite medications, the same active ingredients (afoxolaner, lotilaner, and sarolaner) found in many common monthly flea and tick preventives, has shown complete efficacy against screwworm larvae in dogs at standard doses. Monthly isoxazolines pull double duty as both treatment and ongoing protection. None of these replace hands-on wound care, though; they work alongside the physical removal of every larva, never instead of it.
How Do I Protect My Dog or Cat From Screwworm?
Prevention comes down to habits, not gadgets: keep your pet on year-round parasite prevention, treat every wound promptly, inspect at-risk pets daily, reduce your pet’s exposure to flies and to injuries, and build a broader prevention plan with your veterinary team. None of these steps is dramatic, and that is the point. Small, boring routines are what keep a fly from ever finding an opening.
Day-to-day pet protection against screwworm comes down to treating every wound promptly, checking at-risk animals daily, limiting exposure, and building a parasite prevention plan with your veterinary team.
- Treat every wound promptly: Clean even minor cuts and scrapes right away, and keep them covered and clean while they heal.
- Inspect at-risk pets daily: Run your hands over your dog or cat once a day, checking ears, paws, skin folds, and any healing spot.
- Limit exposure: Keep your pet’s environment clean, manage fly populations around the yard, and supervise outdoor time when you can.
- Mind the extra-vulnerable: Newborns, post-surgical patients, and pets with fresh wounds need closer watching.
- Stay on year-round parasite preventatives: Our online pharmacy has a great range of products in the isoxazoline class that will help prevent not only screwworm, but also fleas, ticks, and mites. Our team is happy to help you choose the best one for your pet.
That daily check is the whole ballgame for pets that spend time outside. Protecting outdoor pets means paying even closer attention to cuts and scrapes, since a dog or cat spending time in the yard has more chances to pick up a wound a fly could find. Indoor pets are lower risk, but they are not risk-free; an open window and a single surgical incision are enough of an opening, so the daily once-over is worth doing for everyone.
Frequently Asked Questions About Screwworm in Pets
Can screwworm affect indoor pets?
Indoor pets are at much lower risk than animals that spend time outside, but the risk is not zero. Screwworm flies are drawn to open wounds, and all it takes is one fly slipping through an open door or window and finding a fresh cut, a surgical incision, or a newborn’s healing navel. If your indoor cat or dog has any open wound, keep it clean and covered, do your daily check, and call us if it starts to look worse instead of better.
Can screwworm spread to people?
A common question is whether screwworm can affect people, and the honest answer is that while it primarily targets animals, it can occasionally infest humans too, which is one more reason to take any suspected case seriously. Human cases are uncommon and generally involve open wounds. In August 2025, the first U.S. human case in 50 years was diagnosed in a traveler who had recently returned from El Salvador, which shows how closely this ties to open wounds and affected regions. That possibility is a good reason not to try picking larvae out of your pet’s wound at home. Let us handle the removal safely, and see your own doctor promptly if you have a wound you are worried about.
What should I do if I find maggots in my pet’s wound?
Treat it as urgent. Do not try to dig the larvae out yourself, because they burrow deep and it is easy to leave some behind, which lets the infestation continue. Instead, keep your pet calm, cover the wound loosely if you can, and call us right away so we can see your pet during our open hours. If it is after hours, head to the nearest veterinary ER. Fast professional care is what turns a scary wound into a very treatable one.
How do I protect my pet when traveling in or through affected areas?
If you are planning travel through affected areas with a pet, inspect for wounds before you leave, keep any breaks in the skin covered and clean, make sure their parasite prevention is current, and give your dog or cat a thorough once-over when you get home. Avoid letting your pet roam unsupervised in unfamiliar areas where it might pick up a cut, and if you spot a wound that worsens after the trip, get it checked promptly rather than assuming it will heal on its own.
Staying Ahead of Screwworm in Fort Worth
The whole strategy here is unglamorous and it works: notice wounds early, clean them fast, run your hands over your at-risk pets every day, keep parasite prevention current, and get us involved the moment something looks off. Screwworm sounds frightening, and an untreated case truly is, but a case caught early is very treatable, and awareness is most of the battle. This is a situation that rewards paying attention.
You do not have to keep track of all this alone. Our experienced veterinarians are your partners as the picture evolves, and we are happy to talk through your pet’s specific risk and build a plan that fits your household. If you have spotted a wound you are unsure about, or you just want to get ahead of this, book a visit online and let us take a look.
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