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LUBBOCK — After the New World screwworm was found in a dog in Texas, pet owners across the state worried how it might affect their animal companions.
But the state’s uncontrollable stray animal population has the potential to make the spread of screwworm worse.
And in some cases, animals in shelters could die as a result of this outbreak, without ever being touched by the screwworm.
“They will do mass, mass, mass euthanasias if they aren’t allowed to move the animals out of the quarantine zones,” said Rebecca Giamona, a veterinarian with Austin Pets Alive. “There could be thousands of animals dying in shelters because they don’t have the space to continue to cover those animals.”
For years, animal advocates across Texas have been raising awareness about the overcrowding in animal shelters all over the Lone Star state. According to Best Friends Animal Society, an animal welfare nonprofit, an estimated 568,325 cats and dogs entered Texas shelters.
Then the New World screwworm burrowed its way to the U.S. The parasitic fly lays eggs in open wounds, which then turn into larvae that feast on the living flesh of warm-blooded animals. And it isn’t limited to cattle, livestock and wildlife — anything with a wound is at risk of attracting the fly. This includes cats, dogs and humans.
Earlier this month, Gov. Greg Abbott issued a statewide disaster proclamation for all of Texas’ 254 counties in response to screwworm cases in the state. The parasitic fly has mostly infested livestock so far, but it was also caught in a dog.
After a screwworm infested zone was established, the Texas Animal Health Commission put quarantine orders in parts of 13 counties: Coke, Edwards, Gillespie, Kerr, Kimble, La Salle, Schleicher, Sutton, Tom Green, Uvalde, Val Verde, Webb and Zavala.
The quarantine orders effectively stop all warm-blooded animals, whether they are infected or not, from being moved out of the infested zone to other areas of Texas or other states. While this does slow the spread of the screwworm, some animal welfare groups worry it could unintentionally exacerbate animal shelter overcrowding.
Giamona is especially concerned for shelters in rural areas. Studies show that rural areas nationwide are under-funded and are often in shelter deserts, where there is little to no access to public animal services.
“They don’t have the resources we do,” Giamona said. “A lot of their setups are completely outdoors with very minimal coverage. So that would make animals in those shelters more susceptible.”
Slowing the spread
Since the first case of the New World screwworm was confirmed in Texas, animal welfare groups, veterinary clinics, and government officials have worked closely together to stop the screwworm from becoming a mass disaster. Part of that work includes having some form of veterinary care for Texans everywhere to report a case.
However, stray animals are still a growing blind spot. There is no guarantee that someone will encounter the animal, let alone take it to a veterinarian if they spot an injury. And now, some animal rescues won’t accept animals from quarantined areas. Austin Pets Alive partners with shelters in South and Central Texas to fill in the gaps. They receive about 2,500 animals a year and work on transporting them to other states. They have 19 partner shelters and transport animals to eight different states as well as Canada.
“We work with these small, under-resourced shelters that otherwise wouldn’t have the resources to care for animals,” said Luis Sanchez, communications officer for the organization. “In most cases, they would euthanize that population.”
Erin Robinson, director of communications for the Texas Animal Health Commission, said the quarantine order keeps animals from moving elsewhere until they are inspected and treated if they have an infestation.
“This way, we can assure our trade partners in other parts of this state, and other states, that we’re not spreading new world screwworm out of this zone if we can help it,” Robinson said.
A quarantine could help slow the spread of the screwworm and potentially stop history from repeating itself. In 1933, during the original screwworm outbreak in the U.S., the pest became more widespread after a shipment of infested animals went from the southwest side of the country to the southeast.
There are other ways to stop the spread of the screwworm. One of the biggest ways is for people to check animals as often as possible, especially ones going into animal shelters or rescues.
“They’re coming from outside, from places that were not controlled, or didn’t have people looking at them on a regular basis,” Robinson said. “We want to make sure thorough inspection happens in order to avoid any infestations.”
Preparing for the worst
The screwworm isn’t contagious and is treatable. However, there are still concerns about what would happen if it managed to get into an area that is crowded with animals. Dr. Virginia DeChant, a veterinarian with the Houston SPCA, said it could be a problem if the maggot falls out of the wound.
“Then it could become an adult fly,” said DeChant, who is one of the seven veterinarians at the Houston SPCA. “Then it could go and lay eggs in another animal.”
A horse at the Houston SPCA wearing a fly mask on June 17, 2026 to protect its eyes from being infested by the New World screwworm. Screwworm frequently enters through openings, such as animals’ eyes. Courtesy of SPCA Houston
The Houston SPCA is based in the fourth largest city in the U.S., but helps animals throughout the region. The organization takes in all species of animals, from cats and dogs, to farm animals and horses. It also has a wildlife center for injured wild animals.
DeChant said nothing has changed for their operations as a result of the screwworm yet. She echoed a sentiment that has been said throughout the outbreak — this didn’t catch anybody in the animal care community off guard.
However, the organization is taking precautions to protect the 500 to 600 animals they take in on a weekly basis. For example, Houston SPCA kicked up its fly control measures in the barn for the farm animals. It also has a spray system that releases Pyranha, a fly control spray, in its barns.
Houston SPCA’s horses also don fly masks and fly boots to protect their eyes and hooves. Both areas are prone to open wounds, like scratches and injuries from being exposed to the environment all day, and the moisture from their large eyes could also attract screwworm flies.
For now, it’s still business as usual. DeChant is encouraging pet owners to make sure their pet’s microchip information is updated, and she’s expecting the border to eventually be closed to companion animals.
“We are keeping a closer eye on animals that come in with open wounds,” DeChant said. “We’re really making sure they’re healing well. The main symptom of the screwworm is that the wounds won’t heal.”
Even if the screwworm infestation is treated by a veterinarian, DeChant said, the healing process is complicated because the wound gets deeper and deeper from the maggots eating the living tissue.
Many of the Houston SPCA’s precautions are things it did before the screwworm. During the intake process, it examined the animals and gave each one parasite prevention so they don’t develop it at the shelter.
The Food and Drug Administration approved Nitenpyram, an over-the-counter medication in tablet form, to treat screwworm in dogs, puppies, cats and kittens. Three other medications have been approved for farm animals.
Giamona with Austin Pets Alive said all of their veterinarians are certified inspectors for the screwworm, and they are getting more of their technicians certified too. They partner with shelters to treat the animals that need it so they can be moved and potentially adopted later on. The organization has also increased public awareness through its Facebook page, where it shares updates on the screwworm.
Robinson with the TAHC emphasized that this is an important time for everyone to report suspected screwworm cases in animals they see.
“We’re asking all animal owners, all people visiting areas where they might encounter wildlife, anyone who might see a stray dog in the parking lot of their local H-E-B, to report anything suspicious,” Robinson said.