Two of Texas’s Deadliest Pests Are Bound to Clash. Will Anybody Win?

Texas now faces the return of the New World screwworm alongside its enormous feral-hog population. Screwworm flies lay eggs in even tiny wounds, producing flesh-eating larvae that can kill livestock within days and threaten ranching operations, meat supplies, pets, and wildlife. Feral hogs may be particularly dangerous carriers because they travel widely, reproduce rapidly, frequently suffer open wounds, and are difficult to monitor or treat. Texas and federal officials are combating the outbreak by releasing millions of sterile male flies, while researchers warn that infected hogs could spread the parasite far beyond current containment areas.

NOTE: this article was originally published to Texas Monthly's Apple News channel on July 8, 2026. It was written by Amanda O'Donnell.

“Two of Texas’s most troublesome invasive species have much in common. They reproduce alarmingly fast, send shudders down the spines of Texas ranchers, and can traverse similar distances (about twelve miles a day). One is the feral hog, capable of outsmarting, outrunning, and outbreeding attempts at its eradication. The other, if presented a pinprick-size opportunity, would eat a live feral hog from the inside out.

The New World screwworm recently returned to Texas, sixty years after the state first fended off the orange-eyed threat. More than thirty cases have been recorded since the confirmed infection of a calf in tiny La Pryor last month. The flying pest inflicts otherworldly horror. It lays its eggs in wounds as tiny as those created by tick bites, and its larvae burrow into and feast on the surrounding flesh.”

“Any warm-blooded animal is vulnerable, but the screwworm is especially worrisome to cattle ranchers. An infestation can devastate a herd, spreading quickly among animals that share close quarters. If a screwworm infection is left untreated, an adult bovine can succumb in under a week. Fighting screwworm is labor-intensive, requires thorough observation and treatment, as well as the quarantining of sick livestock. This can cause supply chain issues and eventually drive up the cost of your steak dinner. 

Meanwhile, Texas has turned into a real pigsty. Our state is home to more feral hogs than any other, and experts estimate that more than half of the country’s entire wild-pig population resides in Texas. John Tomeček, a Texas A&M associate professor of wildlife sciences, pegs the statewide number at between 3.5 million and 6 million. “Those are conservative estimates,” he said. “To give you context, we’re fairly certain there are more pigs in Texas than there are white-tailed deer.””

“Feral hogs cause hundreds of millions of dollars in damage throughout the state each year. Traveling in groups called sounders, they’re known for destructive rooting, using their snouts to pillage rows of crops in search of food, often outcompeting native species in their hunt for edible plants and acorns. They also cause substantial damage to fences, farm equipment, and irrigation systems, leaving a path of disrepair in their wake. 

Could one wildlife problem solve another, with screwworms acting as a natural population check on feral hogs? Possibly. Tomeček said experts speculate that hog numbers have shot up in recent decades in part because there were no longer any screwworms around.

“It’s going to kill pigs, but at what cost? I don’t want to live in a world where screwworms are so widespread that they’re making a landscape-level dent in the feral-hog population,” Tomeček said. “I think if we get to that point, we’ve got an awful lot of problems we’re managing. We may move more screwworms around than kill pigs.””

“It previously took decades to eradicate the pest from American soil. The gold standard in screwworm control involves the mass breeding and releasing of sterile male flies. (It works because female screwworms only mate once in their lifetimes.) In February, in response to a worrisome wave of screwworm spread that began in Central America in 2023, the U.S. Department of Agriculture opened a sterile-fly-dispersal facility in South Texas.

About 100 million screwworms grow to maturity there each week. Pupae are shipped from Panama and then fed a science fiction diet of protein gel made of bovine blood and a milk substitute. They’re dyed fluorescent green (to make them easily identifiable) and incubated before being released by plane or truck along the Texas-Mexico border, as well as near the sites of confirmed screwworm cases. A $750 million addition to the dispersal facility, where screwworms would be bred, is expected to open late next year and would churn out up to 300 million sterile flies weekly.”

“Many of the characteristics that make feral hogs a formidable invasive pest could make them an ideal super-spreader if screwworms take hold in the population. The sorts of open wounds that the flies seek to lay their eggs in can often be found on the sides of tusked male feral hogs after violent scrapes. Hogs reproduce constantly and are capable of birthing two litters of between four and twelve piglets each year. The newborns are particularly vulnerable, with flies often laying their eggs in the umbilical area.

Ranchers are being urged to keep close tabs on their livestock and report any suspicious wounds to the Texas Animal Health Commission. Feral hogs, however, are much more difficult to observe, capture, and treat than domestic animals and other wildlife. They can run at up to thirty miles per hour, hop fences, and travel impressive distances each day. And they’re not particularly friendly. Tomeček also noted that as part of population-control efforts, hogs are often trapped and relocated across state lines to be sold for hunting purposes. This scenario could carry a screwworm infestation to a state less equipped than Texas to address it swiftly.”

““They’re definitely the wild card in the whole situation, because they weren’t in high numbers back when we last had screwworms, so we just don’t know the impact,” said Sonja Swiger, an A&M professor and a livestock entomologist. She urges landowners to check their game cameras and report even a suspected glimpse of a possibly infected hog to Texas Parks and Wildlife. A USDA map tracking screwworm’s spread doesn’t show any infections in feral hogs yet. The confirmed cases so far have been in cattle, goats, and sheep—and two pet dogs that have since been successfully treated.

“Are they more susceptible to these things or less susceptible than other wildlife? We don’t have that information right now. We’re all learning,” Tomeček said. “Pig hide is thicker than some animals’, but the animals are not as careful with themselves. We ask, ‘Is this worse than that?’ I couldn’t hazard a guess, but I do know it’s going to be a problem.””