08/07/2026
While most confirmed cases of New World Screwworm in the U.S. have been detected in cattle, sheep and goats, animal health officials in Mississippi want pet owners to know dogs and cats are vulnerable to the pest.
As of July 24, 42 total cases have been confirmed in Texas and New Mexico. Three of those were confirmed in dogs.
“This pest is still contained in Texas and New Mexico, and there is no reason to panic,” said Carla Huston, Mississippi State University Extension Service veterinarian and professor with the MSU College of Veterinary Medicine. “But it is important to know that any animal is susceptible to these flies and how to protect your pets.”
The New World Screwworm is a type of blowfly that is attracted to wounds and lays its eggs on the living tissue of warm-blooded animals, including livestock, wildlife, pets and less commonly people and birds. Within 24 hours, these eggs hatch into the deadly larvae.
These larvae, or maggots, burrow into the flesh of hosts and cause severe injury and even death if infections are not quickly caught and treated. Animals treated in a timely manner can fully recover.
The risk to animals and people in the U.S. remains low, according to the U.S. Department of Agriculture’s Animal and Plant Health Inspection Service, or APHIS, which monitors and combats the pest.
However, pet dogs and cats are susceptible if they live in or near an area with active infested zones or if they travel to areas with active infested zones, including internationally. Screwworm flies can travel 5 to 9 miles to find a suitable host, Huston said.
The best way to protect pets is to carefully monitor them and make sure they are up to date on flea and tick preventives.
“You want to watch them closely for cuts, scrapes and other wounds and monitor those for infection. Even the smallest wound can attract this fly. It is also important to check body openings and mucus membranes, including noses, ears, vulvas and the corners of the eyes,” she said.
Any cuts, scrapes or wounds on dogs and cats should be kept clean and dry. It is also important to keep animals on flea and tick medications. Even the tiny bites from these pests can attract screwworm flies.
In addition to finding fly larvae, other signs of infection include irritated behavior; head shaking; the appearance of a draining, nonhealing wound; and the smell of decay.
If a pet is suspected of having an infection, contact a veterinarian immediately for evaluation and proper treatment. Several effective medications are available for dogs and cats.
“Even if you find larvae on an animal, it may not be screwworm,” Huston said. “But a veterinarian will need to determine what it is and treat it.”
The Mississippi Board of Animal Health, or MBAH, has set additional interstate movement health requirements for certain warm-blooded animals, including pets, related to New World Screwworm detection in the U.S. For more information about these requirements, visit: https://www.mbah.ms.gov/regulations/chapter-12/
There are also requirements for pet dogs and cats traveling internationally where there are active infested zones of New World Screwworm. For more information, visit the APHIS website: https://www.aphis.usda.gov/animals/animal-health/livestock-and-poultry-disease/stop-screwworm
