Thousands of dogs, cats at risk of euthanasia over screwworm threat

Thousands of dogs and cats in Texas shelters could face an increased risk of euthanasia as state restrictions aimed at preventing the spread of the New World screwworm disrupt a key adoption pipeline that has long helped move animals from overcrowded shelters to homes across the United States.

Federal and state officials have imposed controls on animal movement after the flesh-eating parasite crossed into the U.S. from Mexico for the first time in six decades, creating unintended consequences for pet rescue organizations and shelters.

What Is the New World Screwworm?

The New World screwworm is a parasitic fly whose larvae, or maggots, burrow into and feed on the living flesh of warm-blooded animals, including cattle, wildlife, pets and, in rare cases, humans. Once hatched, these maggots feed on the host, causing painful and potentially fatal infections if left untreated.

According to the U.S. Department of Agriculture (USDA), the pest poses a major threat to livestock and wildlife and was eradicated from the United States decades ago through an extensive sterile-fly release program.

Its recent reappearance has raised alarm among agricultural officials because of the potential impact on the nation’s cattle industry, estimated at more than $113 billion.

The outbreak also prompted federal officials to restrict cattle movements across the U.S.-Mexico border.

How Does Screwworm Affect Pets?

While much of the attention has focused on cattle and livestock, dogs and cats are also vulnerable.

The parasite can infect virtually any mammal, and several recent U.S. cases have been identified in dogs. Animals with wounds, surgical incisions, or skin injuries may be particularly susceptible because the flies seek out openings where they can lay their eggs.

An untreated infection can cause severe tissue damage as the larvae consume living flesh.

Because pets can potentially carry the parasite into new areas, states have imposed restrictions on animal movements from affected regions, creating challenges for shelters and rescue organizations that routinely transport animals across state lines.

Why Texas Is at the Center of the Crisis

Texas has become the focal point of the issue because the outbreak has been concentrated in southern parts of the state near the Mexican border. Dozens of infections have been documented in southern Texas, several involving dogs.

According to the American Kennel Club (AKC), federal and state officials have established 20-kilometer infestation zones around confirmed New World Screwworm cases, introducing quarantines, movement restrictions, and enhanced monitoring efforts to curb the parasite’s spread.

The state is also uniquely dependent on interstate animal transfers.

Texas shelters house far more adoptable animals than local communities can absorb. As a result, rescue groups routinely transport dogs and cats to other states where demand for adoptable pets is higher.

According to data from the American Society to Prevent Cruelty to Animals (ASPCA), Texas transferred nearly 89,000 dogs and almost 53,000 cats out of shelters in 2025, more than any other state. Texas also recorded about 45,000 dog euthanasias and nearly 29,000 cat euthanasias during the same period.

Animal welfare groups say those transfers have become a critical tool for reducing euthanasia rates and easing overcrowding.

Shelters Feel the Impact

The restrictions are already being felt across the state — some states have implemented restrictions on pets coming from screwworm-affected areas. Those measures have significantly slowed or halted animal transport programs that many shelters rely on.

According to data from the AKC, 45 states have implemented New World Screwworm-related animal movement requirements and import rules, while Alaska, Hawaii, Nevada, Ohio, and Wyoming haven’t — although their normal interstate importation requirements still apply.

The Gulf Coast Humane Society in Corpus Christi said it was unable to send rescued dogs into New York for weeks because of the restrictions. During that period, the shelter’s population rose from roughly 325 animals to nearly 450, forcing staff to find additional housing space.

Shelter officials warn that overcrowding can have serious consequences. If rescue organizations can’t accept more animals because kennels are full, municipal shelters may be forced to euthanize additional pets to make space for incoming strays and surrendered animals.

What Happens Next?

For now, animal welfare groups are hoping that expanded screening, veterinary certification requirements, and federal eradication efforts will allow more interstate transfers to resume safely. Some states, including New York, have begun allowing animals from Texas again, provided veterinarians certify they are free of screwworm infection.

However, with 45 states maintaining restrictions on animals originating from affected parts of Texas, shelters remain under pressure. As officials work to contain the parasite, rescue organizations warn that the longer transport disruptions continue, the greater the risk that overcrowding could translate into higher euthanasia rates for dogs and cats awaiting adoption.

Newsweek has contacted the USDA Animal and Plant Health Inspection Service (APHIS) and the ASPCA by email for comment.

Contact Newsweek editors on this story: Ben Kelly and Cristina Diciu.