New World Screwworm Has Been Confirmed in U.S. Dogs-A Vet Shares What Every Pet Parent Should Do
On June 3, the USDA confirmed the presence of a flesh-eating parasite that hasn't been seen in the United States in 60 years. New World Screwworm infects warm-blooded mammals, most commonly livestock, though pets (and rarely, people) can also be at risk.
Fortunately, learning how to protect dogs from screwworms doesn't have to be scary or difficult. I spoke with Dr. Anne Kimmerlein, Global Veterinary Epidemiologist at Mars Veterinary Health, about screwworm symptoms in dogs and cats and how to prevent pets from potentially fatal infestations.
What Is New World Screwworm and Why Are Vets Concerned?
"The New World Screwworm (NWS) is a parasitic fly," Dr. Kimmerlein explains. "Its larvae infest and consume the living flesh of warm-blooded animals."
Most of the time, screwworms enter the flesh after a fly lays its eggs on an animal's open wound. When the eggs hatch, the larvae (or maggots) nourish themselves on the host's flesh as they grow and burrow deeper. Not only can this be a painful and distressing process, but it can also be fatal if left untreated.
New World Screwworms (NWS) are native to South America and the Caribbean, but in recent years they have been spreading northward through Central America and Mexico.
Dr. Kimmerlein explains that NWS can also be transmitted through the transportation of infected animals. This is why international travel and the transportation of pets may be impacted. Those traveling internationally with animals should stay informed by reading the latest updates from the USDA.
It's less likely to see screwworms in dogs or cats than in cattle and other livestock, but pets can be affected. One of the confirmed cases is a dog in Lea County, New Mexico, though the dog's travel and exposure history have not been confirmed.
How to Protect Dogs From Screwworms
These parasitic pests and their effects on animals may sound scary, but awareness and responsiveness can keep pets safe all summer long. These are the screwworm symptoms in dogs and cats that Dr. Kimmerlein urges pet parents to look out for:
- A wound that rapidly increases in size.
- Visible larvae that appear to be burrowing into the wound.
- The presence of egg masses on or near a wound.
- Behavioral changes such as lethargy, loss of appetite, or avoidance of contact.
If a pet parent suspects their pet is infested with NSW, she advises, they should not attempt to remove the larvae or treat the wound at home. Not only do veterinarians have the proper tools and knowledge to treat this complex condition, but they also know the correct protocol for reporting the case to state and federal authorities.
Prevention is the best way to protect pets and farm animals from screwworms, and it can be as simple as regularly checking animals for wounds. Dr. Kimmerlein encourages pet parents to keep animals and their environments clean and to ensure that any wounds are properly treated. Additionally, families with pets should familiarize themselves with how different species express pain, because some wounds can be incredibly hard to see.
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Generally, pet parents shouldn't panic over this news about the New World Screwworm. The veterinarian confirms that the overall risk to people and pets is low, though a little knowledge and hygiene can go a long way in keeping pets protected all summer long.
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This story was originally published June 11, 2026 at 4:45 PM.