You may have seen the alarming headlines about a “flesh-eating maggot” reaching the United States. The pest is real, the concern is legitimate, and — for the first time in decades — it’s now being found in animals on U.S. soil, including at least one pet dog. But the panic in the coverage tends to outrun the practical facts a pet owner actually needs. I’m an internal medicine and infectious disease physician, not a veterinarian, so I’ll be clear about where the line is: the details of treating an animal belong to your vet. What I can do is explain what this parasite is, why it’s suddenly back, what it means for the animals in your home, and how to recognize trouble early.
What New World screwworm actually is
New World screwworm is the larva of a parasitic fly, Cochliomyia hominivorax [1]. Here’s what sets it apart from ordinary maggots, which feed on dead tissue: screwworm larvae burrow into the living flesh of warm-blooded animals, using mouth hooks to feed and dig deeper [2]. A female fly lays her eggs at the edge of a wound — even a small one — or around a body opening. The larvae hatch, tunnel into healthy tissue, enlarge the wound, and that growing wound attracts still more flies. Left untreated, an infestation can become severe and, in animals, sometimes fatal [2].
The condition of having fly larvae in living tissue has a medical name — myiasis — and screwworm is one of its more aggressive causes. It primarily affects livestock, pets, and wildlife, and less commonly people [2].
Why it’s back — and why it’s now in the U.S.
This is where a little history helps. Screwworm was once a serious livestock pest in the United States, and the country eradicated it back in the 1960s using an ingenious method: mass-releasing sterilized male flies so that wild females mate but produce no offspring, collapsing the population [7]. That “sterile insect technique” pushed the pest south and held a containment line in Central America for decades.
That line has broken. The parasite re-emerged in Mexico in November 2024 and spread northward [7]. As of mid-2026, Central American countries and Mexico had reported more than 185,000 animal cases and over 2,000 human cases [1]; an earlier CDC advisory in January 2026 already counted at least seven human deaths in the region [4]. Then it crossed the border: on June 3, 2026, USDA confirmed the first U.S. animal case of this outbreak — a three-week-old calf in Zavala County, Texas [5]. Within days, additional animals tested positive, including a pet dog in Lea County, New Mexico [7]. The CDC activated an emergency response in June 2026 to support the effort [6].
I want to keep this proportionate, because proportion is exactly what the headlines lose. There have been no locally acquired human infestations in the United States, and public health agencies describe the risk to people as low [1,6]. The response is substantial — renewed sterile-fly releases along the border, animal movement controls, and surveillance [3]. But the arrival of cases in U.S. animals is why pet owners in affected regions should pay attention now rather than later.
What this means for your pets
Dogs, cats, and other animals become infested the same way livestock do: through a wound or a natural body opening where a fly can lay eggs [5]. That reframes the risk usefully. Screwworm isn’t something that drifts onto a healthy, intact animal out of nowhere — it exploits broken skin. So the pets at higher risk are those with cuts, scrapes, surgical sites, tick-bite sores, or raw areas from scratching, along with newborn animals, where the healing navel is a classic target [5]. Animals that spend time outdoors in affected areas, or that travel to or from regions with active cases, carry more exposure.
If you don’t live in or travel to an area with active cases, your day-to-day risk right now is low. If you do, this moves onto your radar.
How to spot it early
Early recognition matters enormously, because a small infestation is far easier to handle than a large one. USDA advises animal owners in affected areas to check pets and livestock for a few specific signs [5]:
A wound that’s draining, enlarging, or not healing the way it should. An animal that seems uncomfortable, agitated, or bothered by a particular spot. And — the unmistakable one — visible larvae or eggs in or around a wound or a body opening such as the nose, ears, or genitals, or the navel of a newborn [5]. Screwworm wounds are sometimes noted to have a distinctive odor. If you see maggots in a living animal’s wound, that is not something to watch and wait on.
What to do — and what not to do
Here’s the part where I’ll be firm, because instinct can lead people astray. Do not try to dig the larvae out yourself or treat this at home with whatever’s in the cabinet. Screwworm is a reportable pest, and both the animal and the public-health response depend on proper handling.
If you suspect your pet is infested, contact your veterinarian immediately, and report it to your state animal health official or the USDA [5]. Treatment is genuinely a veterinary matter — it involves removing larvae, managing the wound, and appropriate medication. Regulators have moved to expand options here; the FDA has authorized a generic over-the-counter drug for treating screwworm in dogs and cats during this outbreak [6]. But “available” is not the same as “self-administer without guidance” — let your vet direct treatment and reporting, because catching and documenting cases is how the broader eradication effort actually works.
Prevention, including travel
Prevention follows directly from how infestation happens. Keep your pet’s wounds clean and covered, and treat minor injuries promptly rather than letting them fester. In affected areas, check your animals regularly, especially any with existing sores or after outdoor time.
Travel deserves special mention. Bringing pets or service animals into the U.S. from countries with active screwworm must meet specific USDA and CDC import requirements [3], and it’s worth checking those rules — and talking to your vet — well before any cross-border trip with an animal. The same environmental precautions that protect people (insect repellent, avoiding areas dense with infested animals) reduce exposure for pets too.
A brief word on people
Because this is an infectious-disease story as much as a veterinary one, a note on the human side. Human screwworm infestation is uncommon and the current U.S. risk is low, but it’s not zero — the one U.S. human case in this outbreak was in a traveler returning from El Salvador in August 2025 [1]. For anyone traveling to affected countries, the standard advice applies: clean and cover any wounds, use insect repellent and protective clothing, and sleep in screened or netted spaces [3]. If a person develops a wound with larvae, that warrants prompt medical attention.
Bottom line
New World screwworm is a serious animal-health threat that has, for the first time in generations, reached U.S. soil — including a pet — which is why awareness right now is sensible rather than alarmist. For most pet owners the immediate risk remains low, and it’s concentrated in animals with wounds in areas where the pest is active. The practical playbook is simple: keep wounds clean and covered, check your animals in affected areas, and if you ever see larvae in a living animal’s wound, treat it as an emergency — call your veterinarian and report it, don’t handle it yourself. Because this outbreak is changing week to week, the government’s live tracker at screwworm.gov is the place to confirm where cases currently stand.
Do you have questions about how outbreaks like this get tracked and controlled, or about the science of the sterile-fly method? Ask in the comments — please keep it general, and for anything about your specific pet or your own health, contact your veterinarian or physician directly.
This article is for general educational purposes and does not replace veterinary or medical care. If you’re concerned about an animal, contact your veterinarian; for concerns about your own health, contact a qualified clinician.
References
- Centers for Disease Control and Prevention. New World Screwworm Outbreak — Situation Summary.
- Centers for Disease Control and Prevention. New World Screwworm (About).
- USDA Animal and Plant Health Inspection Service. Stop Screwworm (screwworm.gov).
- Centers for Disease Control and Prevention. HAN Health Advisory: New World Screwworm — Outbreak Moves into Northern Mexico. January 20, 2026.
- USDA-APHIS. USDA Confirms Presence of New World Screwworm in the United States. June 3, 2026.
- Centers for Disease Control and Prevention. CDC Activates Emergency Operations Center for New World Screwworm Response. June 2026.
- Swine Health Information Center. USDA Confirms New World Screwworm Detections in Texas and New Mexico in June 2026.
