Screwworm Dog Symptoms: What US Owners Must Know

A parasite the United States wiped out sixty years ago is back — and this time it has reached pet dogs. On 28 October 2026, Arizona confirmed its first New World screwworm case in a dog in Cochise County, the third US state to record the parasite after Texas and New Mexico. On 3 November, the US Food and Drug Administration (FDA) issued an emergency authorisation for Bravecto chewable tablets to treat screwworm infestations in dogs and puppies. If you own a dog, here is what the parasite is, the symptoms to watch for, and what to do — calmly, and with the facts exactly as the authorities have reported them.

Direct Answer: New World screwworm is a parasitic fly whose larvae feed on living tissue in open wounds. As of 29 October 2026, the US Department of Agriculture (USDA) had confirmed 74 animal cases in the United States since June, rising to 79 by 1 November. Ten of the cases counted in early November were pets — nine dogs and one domestic cat — with cases in Texas, New Mexico and Arizona. The warning signs are maggots or a foul smell in a wound or body opening, a wound that worsens quickly, and bleeding from an open sore. If you see any of these, seek veterinary care immediately. The FDA authorised emergency use of Bravecto (fluralaner) chewable tablets for dogs and puppies on 3 November 2026; it is prescription-only. Most dogs in the US remain at low risk, according to the FDA.

Key Takeaways

• **Screwworm is back in the US after sixty years:** the first case of the current outbreak was a calf in Texas on 3 June 2026, and cases surged in October.
• **74 confirmed animal cases as of 29 October, 79 by 1 November** — ten of the cases counted in early November were pets: nine dogs and one cat.
• **The symptoms are wound-focused:** visible maggots, a foul smell, a wound that worsens or bleeds, and pain or unusual behaviour.
• **The FDA authorised emergency use of Bravecto** (fluralaner) chewable tablets for dogs and puppies on 3 November 2026 — prescription-only, through a licensed vet.
• **Most US dogs remain at low risk**, according to the FDA, because confirmed cases are in a limited geographic region.
• **Prevention is simple and practical:** check your dog for wounds every day and keep any wound clean and covered.

What is New World screwworm?

New World screwworm (Cochliomyia hominivorax) is a parasitic blowfly. The female fly lays eggs in open wounds or natural body openings of warm-blooded animals — including dogs, livestock, wildlife and, rarely, people. The eggs hatch into larvae, or maggots, that feed on living tissue rather than dead flesh, burrowing deeper as they grow and widening the wound with every hour that passes. Left untreated, a serious infestation can kill an animal.

The United States eradicated screwworm in 1966, and for decades it was held back by releasing sterile male flies along the Panama–Colombia border. In 2023 the fly broke through that barrier and moved north through Central America and Mexico. The first US animal case of the current outbreak was confirmed on 3 June 2026, in a calf in Zavala County, Texas.

The outbreak moved slowly through the summer — only eight cases were reported across August and September — and then surged in the autumn. October alone produced 22 cases as of 29 October, making it the second-busiest month since the outbreak began. That surge is why the story is in the news now, and why dog owners in the affected region are being asked to check their animals daily.

What are the symptoms of screwworm in dogs?

The signs are all wound-focused, and they are distinctive enough that the authorities have described them in plain terms. The FDA says dogs should be closely monitored for "visible maggots or foul odors in wounds or body openings (e.g., eyes, ears, nose, mouth)". The Centers for Disease Control and Prevention (CDC) lists the following warning signs:

• Feeling or seeing maggots (larvae) move in a skin wound or sore, or in the ears, nose, eyes or mouth
• Painful skin wounds or sores that worsen within a few days
• A foul-smelling odour from the site of the infestation
• Bleeding from open sores

Veterinarians add two details worth knowing. Arizona State Veterinarian Ryan Wolker described the hallmark wound as having "a significant odor (and) a significant cavitation", with the maggots aligning themselves in a vertical pattern inside the wound, "kind of like if you're looking at the head of a sunflower". The American Animal Hospital Association notes that affected animals show signs of pain — depression, irritability, loss of appetite and isolation from others — and that wounds become deeper and larger as the maggots grow and feed.

Two practical points follow from this. First, the wound does not have to be large: the CDC notes that wounds as small as a tick bite can attract an egg-laying female fly. Second, the signs develop fast — a wound that was minor yesterday and is suddenly larger, smellier or bleeding today deserves a vet call the same day, not a wait-and-see approach.

How many cases are there, and where?

The numbers are moving, so the dates matter. As of 29 October 2026, the USDA had confirmed 74 animal cases in the United States since June, with 21 of them active, according to a case tracker based on USDA data. By 1 November the total had reached 79.

A breakdown of the cases counted in early November shows where the parasite is hitting. Of 73 cases in domestic animals, 35 were in cattle, 17 in sheep, nine in dogs, seven in goats, four in horses and one in a domestic cat — ten pets in total. One case was in wildlife, a female elk in Pecos County, Texas, the first in US wildlife during this outbreak. Active cases at that point were concentrated in New Mexico (12), Texas (8) and Arizona (1).

Arizona's first case is the one most dog owners have heard about. On 28 October, the USDA confirmed an infestation in a ranch dog in Cochise County, in the southeastern corner of the state. A local vet had examined the dog on the evening of 26 October and found a wound on its back heavily infested with maggots. Laboratory testing at the USDA's National Veterinary Services Laboratories in Ames, Iowa confirmed screwworm, and the dog has since recovered. State and federal officials established a 20-kilometre infested zone around the detection site and released about a million sterile male flies to reduce reproduction. A second Arizona detection followed three days later, on Halloween, in a horse in the same county.

New Mexico reported the first US case in a cat around the same time, and five new pet cases were confirmed within a few days — four dogs in Arizona, New Mexico and Texas, and the cat in New Mexico. The pattern is consistent: the parasite is spreading west and north, mostly in livestock, but pets are now part of the case count.

What did the FDA do on 3 November?

On 3 November 2026, the FDA issued an Emergency Use Authorization (EUA) for Bravecto (fluralaner) chewable tablets for the treatment of New World screwworm infestations (myiasis) in dogs and puppies. The authorisation was issued to Intervet Inc., based in Rahway, New Jersey, and is listed as EUA 006767.

The FDA said that, based on the totality of the scientific evidence available, it is reasonable to believe Bravecto may be effective against screwworm myiasis in dogs and puppies when used as authorised, and that the known and potential benefits outweigh the known and potential risks. Bravecto was already approved for various flea and tick indications in dogs and puppies; this authorisation adds the screwworm use.

Three things about the authorisation matter for owners. First, an EUA is not a full approval — it is a targeted emergency measure that lets a drug be used for a new purpose during a declared public health emergency, and it stays in effect only until the FDA revokes it or the Secretary of Health and Human Services ends the declaration. Second, Bravecto is prescription-only: fluralaner belongs to the isoxazoline class of antiparasitic drugs, which have been associated with neurologic adverse reactions including muscle tremors, loss of coordination and seizures, so professional expertise is required to monitor for and respond to those reactions. Dog owners should consult a veterinarian to determine whether Bravecto is appropriate for their dog. Third, this is the latest in a series rather than a one-off: as of 3 November, the FDA had issued 16 emergency use authorisations and three conditional approvals for animal drugs against New World screwworm.

Bravecto is a prescription medicine and is not sold by Advance Pet Mart. Nothing in this article is a recommendation to use it — that decision belongs to your vet.

What should you do if you suspect screwworm?

The FDA's instruction is short and direct: seek immediate veterinary care for infested dogs. Do not wait to see whether the wound improves on its own. Screwworm infestations are treatable if caught early but can be deadly if left alone, and the larvae keep feeding and burrowing while you wait.

Do not try to remove the larvae yourself. Removing all the eggs and larvae is a job for the vet — in human cases the CDC notes it can even require surgery when maggots are deeply embedded — and the wound needs professional cleaning and treatment afterwards. What you can do while you get to the vet is keep your dog calm, keep flies off the wound, and cover it if you can do so safely.

Tell your vet about any travel. The FDA says dogs that live in, travel to, or return from areas where screwworm has been identified by state or federal animal health officials — as well as certain countries south of the US border — should be closely monitored for signs of infestation. That travel history changes how urgently a wound is treated.

Finally, report it. Officials urge owners to report suspected cases to their state veterinarian promptly, so the response — infested zones, sterile fly releases, movement controls — can start quickly. In Arizona, suspected cases should be reported to the Arizona Department of Agriculture on 602-542-4293.

How can you lower your dog's risk?

The prevention advice from the CDC and state officials is refreshingly simple, because the fly needs one thing: an open wound. Deny it one.

• Check your dog for wounds every day, especially after outdoor activity. Run your hands over the whole body and look at the ears, eyes, paws, tail base, genitals and any surgical site — and anywhere your dog keeps licking.
• Keep every wound clean and covered, no matter how small. A wound as small as a tick bite, a scratch, or a fresh injection site can attract an egg-laying fly.
• Cover healing surgical sites and keep flies away from them while they heal.
• Be extra careful when travelling with your dog to Texas, New Mexico or Arizona, or south of the border. Dogs entering Mexico currently need a specific screwworm inspection document signed by a USDA-accredited veterinarian and issued within five days before entry.

None of this requires special equipment — just attention, clean water, and something to cover a wound with. That is the unglamorous truth of screwworm prevention, and it is also why the authorities keep repeating it.

What does "low risk" actually mean?

"Most dogs in the US are at low risk" is the FDA's exact position, and it is worth understanding rather than just repeating. The reason is geographic: confirmed cases are in a limited region — so far, parts of Texas, New Mexico and Arizona. If your dog lives far from those areas, has no open wounds and has not travelled there, the risk is genuinely low.

The CDC's position on people is the same: the risk to the general US public is very low, and there have been no locally acquired human cases in the United States during this outbreak.

Low risk is not no risk, and the trend is the reason for the attention. The parasite reached a third state in October, October was the second-busiest month of the outbreak, and cases are still being found daily in the affected states. Risk concentrates in three situations: living in or near an affected area, having an open wound, and travelling with your dog to an affected area or south of the border. If none of those apply, there is no reason to change your dog's routine — but the daily wound check is worth doing anyway, because it catches far more ordinary problems than screwworm.

Shop our pet first aid and wound care collection

Screwworm itself is treated by a vet, with prescription medicine — not by anything on a pet store shelf. What you can do at home is the part the CDC and the FDA both stress: keep wounds clean, covered and checked. These are the wound-care essentials we stock for exactly that job.

• Pet First Aid Trauma Kit – Complete Emergency Wound Care Kit — all the necessary first aid products in one place, for the scenario every owner dreads: a torn-open wound and a dash home.
• Pet Wrap Bandage – Self-Adhering Stretch Tape by Simple Solutions — self-adhering bandage tape that holds dressings in place on active pets and supports weak or injured limbs. No clips or tape needed, and it will not stick to your pet's coat.
• PawFlex Basic Bandages – Disposable Non-Adhesive Stretch Bandage — a disposable, non-adhesive, fur-friendly super-stretch all-in-one bandage that takes seconds to secure and release.
• Pawflex Medimitt Paw Bandage – No Front or Back Wound Wrap — a paw bandage with no designated front or back, so the wound pad can face any direction on the paw, with a non-slip Velcro fastener.

To be clear: none of these products treats, prevents or is certified for screwworm. They are general first-aid supplies for everyday cuts, scrapes and bandaging — the everyday wound care that also happens to be your first line of defence against the fly. Browse the full Dog Health & Supplements collection and the wider Health collection to compare options.

Frequently asked questions

Can my dog catch screwworm from another dog?

No. The only way to be infected is for a screwworm fly to lay eggs in an open wound or other body opening. It does not spread from dog to dog, or from a dog to its owner. The fly is the carrier, and the wound is the doorway.

Is Bravecto now approved for screwworm?

Not as a full approval. The FDA issued an Emergency Use Authorization on 3 November 2026, which allows prescription use for screwworm in dogs and puppies during the declared emergency. It is available only by prescription from a licensed veterinarian, who decides whether it is appropriate for your dog.

Should I check my dog for wounds every day?

Officials advise daily checks in affected areas, and it is a good habit everywhere. Wounds as small as a tick bite can attract an egg-laying fly, and the daily check is also how you catch ordinary cuts, hot spots and ticks early. Make it part of the evening routine — a quick hands-on check while your dog settles down.

What should I do if I find maggots in my dog's wound?

Get veterinary care immediately — this is an emergency vet visit, not a home treatment. Do not try to pull the larvae out yourself; removal and treatment need a vet, and the wound needs professional cleaning. Keep your dog calm, keep flies off the wound, and cover it if you can do so safely on the way.

Is my dog at risk if I live far from Texas, New Mexico or Arizona?

According to the FDA, most dogs in the US remain at low risk because confirmed cases are in a limited geographic region. The risk rises if your dog travels to an affected area, or to certain countries south of the US border, and if your dog has open wounds. Distance helps, but the daily wound check is still worth doing.

Can people get screwworm?

Yes, rarely — the fly lays eggs in open wounds on any warm-blooded animal, including people. The CDC rates the risk to the general US public as very low, and no locally acquired human cases have been reported in the United States during this outbreak. The advice is the same as for dogs: keep any open wound clean and covered, and contact a healthcare provider if you see or feel maggots in a wound.

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This article is for informational purposes only and is not veterinary advice. If your dog shows any of the signs above — especially maggots or a foul-smelling wound — see your veterinarian right away. At Advance Pet Mart, we hope your dog never meets this parasite — and that if it does, you catch it early.

Sources: the FDA's Emergency Use Authorization announcement for Bravecto via FDA.gov and the FDA's Animal Drugs for New World Screwworm page; dvm360 on the authorisation; Reuters, 3 November 2026; case counts and the pet breakdown via Medical Daily and Meatingplace; symptom guidance from the CDC via azcentral and the CDC situation summary.