Screwworm closed the cattle border, and 44 states closed the door on Texas shelter dogs

The New World screwworm has crossed from Mexico into the United States for the first time in 60 years, and the control response has stalled adoptions for thousands of dogs and cats in Texas, putting some of them at risk of euthanasia ^[1]. The parasite threatens a $113 billion beef industry, which is why federal officials closed the border to cattle movements ^[2]. The part nobody planned for is what happened next to an entirely different supply chain.

The fly lays eggs that hatch into flesh-eating larvae in wounds or mucous on any mammal, and several of the dozens of infections recorded in southern Texas and southeastern New Mexico have been in dogs ^[3]. Because pets are susceptible, 44 states have restricted movement of animals out of infested areas ^[4]. That is all but six of the 50 states ^[5]. Texas shelters that normally ship thousands of animals a year to other regions were left holding them ^[4].

The scale of that dependency is the whole story. In 2025 Texas transferred nearly 89,000 unadopted dogs out of its shelters, more than any other state, according to the American Society to Prevent Cruelty to Animals ^[6]. The same year it euthanized about 45,000 dogs, also more than any other state ^[7]. Roughly two dogs left the state alive for every one killed in a shelter ^[8]. Texas also led in cats transferred out, at nearly 53,000, and trailed only California in cats euthanized, at almost 29,000 ^[9]. It holds about 439,000 stray dogs and cats, second only to California ^[10]. Warm weather lets strays survive and breed longer, and veterinarians and welfare advocates say Texas owners are less inclined to spay or neuter ^[11].

Out-of-state transport is not a nice-to-have in that arithmetic. It is the primary outflow, and it was interrupted by a rule written about cattle flies.

The Gulf Coast Humane Society in Corpus Christi, which sends about 500 dogs a year outside Texas, could not get rescued dogs into New York for weeks, and its population climbed from around 325 to nearly 450 ^[12][13]. That is roughly 125 additional animals, a 38 percent increase, absorbed by building out outdoor exercise areas ^[14][13]. New York eventually reopened to Texas dogs on the condition that a veterinarian certify each one free of screwworm ^[13]. Mia Bendixsen of the Texas Humane Legislation Network said the restrictions threw a wrench into things for small rescues as well as bigger shelters ^[15]. When one shelter cannot take animals from municipal shelters, the source reports, those shelters euthanize more ^[16].

In Houston, Humane Society shelter director Aaron Grady said animals that cannot be moved out become more stressed, and that a barking, wall-bouncing dog looks less adoptable than a calm one in the next kennel ^[17]. That shelter holds its population near 200 by using foster homes for up to 300 more, an effective capacity of about 500 ^[18][19].

What to watch is the timeline mismatch. The USDA's $750 million sterile-fly factory in southern Texas, intended to breed billions of sterile males, is not set to open until April 2027 ^[20]. Until then the work falls to smaller facilities in Texas and southern Mexico dispersing flies bred in Panama, with another planned for Arizona ^[21]. The technique is proven: sterile males released from planes largely eradicated the fly by the early 1970s ^[22]. But movement restrictions are the cheap interim tool, and the cost is being paid in kennel space.