Most pet owners living in the South have never thought about screwworms. Why would they? The US eradicated New World screwworm (NWS) in 1966, and for sixty years it stayed gone. That changes now. On June 3, 2026, USDA APHIS confirmed the first US detection in a calf in Zavala County, Texas, and by early July, two confirmed cases had shown up in dogs, part of more than 30 total confirmed instances across Texas and New Mexico. This is not a theoretical threat anymore. It’s here, it’s in pets, and if you own a dog or cat anywhere in the region, you need to know what you’re actually dealing with.

I’ll be honest: when I started digging into this, I assumed screwworm was basically a livestock problem that occasionally touched pets at the margins. What surprised me was how quickly veterinary and agricultural experts shifted their language to explicitly name dogs as vulnerable, and how the risk factors map onto exactly the kinds of dogs many people in Texas and New Mexico keep or rescue. Agriculture Secretary Brooke Rollins stated the outbreak may continue for at least a few more months, with officials deploying sterile fly releases to suppress the population, so this isn’t going away by the time you read this.

According to reporting from PBS NewsHour on July 9, 2026, NWS larvae (Cochliomyia hominivorax) eat live flesh and fluids, not dead tissue, which is what makes this fly so dangerous and so different from the blowflies most of us have seen around a wound. A wound that looks minor can become a deeply infested mass within 24 hours if a female fly lays eggs in it.

Key takeaways
  • NWS confirmed in US dogs by July 8, 2026; 30+ total cases across Texas and New Mexico
  • Larvae eat live tissue and can kill a pet within days if untreated
  • Free-roaming, stray, and recently rescued dogs face the highest risk
  • Starting August 3, 2026, dogs and birds traveling to Mexico need USDA inspection certificates
  • Any open wound in a high-risk area warrants same-day veterinary evaluation, not watchful waiting

Why This Parasite Is Genuinely Different From What You Know

Most fly larvae people encounter are nuisance blowflies that colonize dead or decaying tissue. NWS is not that. The larvae of Cochliomyia hominivorax actively burrow into living tissue, releasing enzymes that liquefy muscle and skin while they feed. They’re attracted to wounds as small as a tick bite or a scratch. They can infest ear canals, the tissue around the mouth, the eyes, and the genitals, not just obvious traumatic wounds. An infestation can go from a few eggs to a pocket of hundreds of larvae in 12 to 24 hours.

That timeline matters enormously for how you respond. This is not a “watch it over the weekend” situation. If your dog has any open wound and you’re in an affected area, same-day veterinary evaluation is the right call. I know that feels like an overcorrection, but the math on NWS doesn’t favor waiting.

Who’s Actually at Risk Right Now

Recommended Vet-Approved Dog First Aid Kit with Tick Remover

Essential pet emergency kit with first aid guide, slip leash, and medical supplies for home, car, and camping.

Check Price →

Helpful resource: Thundershirt Classic Dog Anxiety Jacket is a top-rated option for this. (As an Amazon Associate this site earns from qualifying purchases.)

The AKC Canine Health Foundation, in a June 11, 2026 article, identified free-roaming dogs, strays, transported animals, and recently rescued dogs as carrying the highest risk, because they’re more likely to have undetected wounds and less likely to have received routine preventatives. If you foster, rescue, or work with a rescue organization in Texas or New Mexico right now, this is the group you need to be most worried about.

That said, any dog with an open wound, including a surgical incision, a tick-bite lesion, a small cut, a hot spot, or a skin fold infection, is potentially vulnerable if flies have access to them. Outdoor dogs are more exposed than indoor dogs, but the AKC guidance doesn’t let indoor dogs fully off the hook if they spend time outside.

Cats are currently considered lower risk. They’re exempt from the new travel inspection requirements, and there are no confirmed NWS cases in US cats as of the reporting I reviewed. The biological reason isn’t entirely clear from the literature, but cats’ grooming behavior and wound management instincts may play a role.

Recognizing the Signs: What Owners Are Actually Seeing

The early window for NWS is small. Here’s what the reporting from the Texas Tribune and Texas A&M AgriLife describes as the progression:

StageWhat You Might SeeTime Since Infestation
EarlySmall wound with unusual odor, restlessness, wound-directed licking12–24 hours
Active infestationVisible larvae (cream/white, 1–2 cm), expanding wound, seeping fluid24–72 hours
SevereDeep tissue destruction, blood-tinged discharge, neurological signs72+ hours
Life-threateningSepsis, collapse, organ failureDays without treatment

The smell is frequently the first thing owners notice. People describe it as a sharp, distinctive, almost sweet-rotten odor that’s different from a normal infected wound. If your dog is fixated on licking a spot that you thought was a minor wound, and it smells wrong, look closer. Part the fur, examine the wound with a flashlight. Larvae are visible to the naked eye.

Do not attempt to remove larvae at home. The removal process requires veterinary handling because larvae that are ruptured inside the wound release substances that can cause serious allergic reactions. This is one of those situations where “I’ll try to handle this myself” genuinely makes the outcome worse.

The New Travel Rules and What They Mean Practically

Starting August 3, 2026, if you’re traveling with a dog or a bird to Mexico, you need a USDA inspection certificate, per AVMA reporting. Pet cats are currently exempt from this requirement. This is a direct response to the NWS detections and is meant to prevent the spread from moving further across the border in either direction.

Practically, this means scheduling a USDA-accredited veterinarian appointment before any travel, not just your regular vet, because not every clinic is accredited for USDA health certificates. If you’re near the Texas-Mexico or New Mexico-Mexico border and regularly cross with your dog, this is now part of your travel checklist. The certificates aren’t instantaneous. Give yourself at least a week’s lead time, more if you’re in a busy border region.

If you’ve recently moved a dog up from Mexico or the Texas/New Mexico border area in the last several weeks, and the dog has any wound history, mention that explicitly to your vet. Transported animals are specifically flagged as high-risk in the guidance from the AKC Canine Health Foundation.

Prevention: What Actually Works Right Now

The research here is somewhat mixed on which specific preventatives are most effective against NWS specifically, because this is a newly re-emerged threat in the US and clinical data in dogs is still developing. What veterinarians are recommending based on current guidance:

Keep wounds covered and cleaned. Flies lay eggs in open wounds, so any wound management that reduces fly access reduces risk. Clean wounds daily with chlorhexidine or saline, apply appropriate wound dressings, and keep the animal indoors when possible.

Talk to your vet about topical and systemic parasiticides. Some products used for myiasis prevention in livestock have analogs discussed in small animal medicine, but this is a conversation to have with your specific vet given your dog’s health status and the products available in your area. Do not apply livestock wound sprays to pets without veterinary guidance.

Limit exposure during peak fly activity, which is typically dawn and dusk in warm weather. If your dog has a healing wound, that’s not the week for all-day outdoor access in an affected county.

The screwworm situation in the US is going to evolve over the next several months. Sterile fly releases are the same method that worked in the 1966 eradication, and they can work again, but it takes time. In the meantime, the best thing a pet owner in Texas or New Mexico can do is keep a close eye on any wound, know what early infestation looks like, and not talk themselves out of calling the vet because the wound looks “small.”

Sources

Photo: Ipsita Naskar via Pexels

This article is for general informational purposes only and does not constitute veterinary advice. Pet health symptoms can have many causes and require professional evaluation. Always consult a licensed veterinarian for diagnosis and treatment specific to your pet.

Disclosure: As an Amazon Associate, we earn a small commission from qualifying purchases at no extra cost to you. We only recommend products that genuinely support the topics covered in this article.