Flesh-eating parasite screwworm returns to US Southwest, threatening pets and livestock

Screwworm, a dangerous parasitic fly whose larvae feed on living animals, has returned to the US Southwest for the first time in decades, raising concerns for livestock, wildlife, and household pets. The pest's reappearance marks its northward spread from Central America and Mexico.

Veterinarians are urging pet owners, especially those near the US-Mexico border, to be vigilant for specific symptoms. These include wounds that swell, ooze pus, or fail to heal, as well as signs of animal distress like excessive licking, lethargy, or loss of appetite. A particularly telling sign is a foul odor of rotting flesh emanating from a wound. Experts emphasize that any suspicious wound warrants a veterinary visit, even if maggots are not immediately visible.

Stray animals are considered most at risk and could act as vectors for spreading the parasite to domestic pets. Residents are advised to monitor strays and contact animal control if screwworm infestation is suspected. "The consequences of missing one or two cases is so great that if the public sees anything suspicious, take it into your vet,” said Dr. Pancho Hubert, president of the Texas Veterinary Medical Association. “It might not be anything, but these wounds carry so much significance.”

Prevention may be possible through regular use of monthly parasite medications, such as those used for fleas and ticks, as these can kill parasites feeding on the animal. Treatment by a veterinarian typically involves removing larvae and eggs, cleaning the wound, and administering antibiotics. Animals treated early generally survive.

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The consequences of missing one or two cases is so great that if the public sees anything suspicious, take it into your vet. It might not be anything, but these wounds carry so much significance.