Texas Cattle Ranchers Brace for the Comeback of a Devastating Flesh-Eating Pest

Chris Womack stands as one of the few Texas ranchers who vividly recalls the battle against the New World screwworm, a pest that was once eradicated but is now threatening to return to the U.S. after reappearing in northern Mexico.

“You never forget the smell,” Womack, 60, reminisced about his first encounter with a calf infested with screwworm maggots. This was just one of many cases he and his father treated during the early 1970s when an outbreak devastated Texas ranchers. The screwworm parasite can kill cattle in less than two weeks, making it a formidable foe.

Now, over 50 years later, Womack and fellow Texas cattlemen are preparing for the potential resurgence of this pest. Reports of cases are increasing in a Mexican state bordering Texas, as the screwworm has escaped the containment efforts of an international eradication program that had kept it at bay for decades. In response, Texas Governor Greg Abbott issued a disaster declaration last week to mobilize state resources for the screwworm response.

The return of the screwworm could severely impact the $130 billion U.S. cattle industry, which is already grappling with a record-low herd and rising operational costs. The screwworm’s presence led to a ban on cattle imports from Mexico for much of the last 14 months, further straining American beef producers at a time when beef prices are at an all-time high, causing frustration among consumers facing rising food costs.

The eradication program, which relies on releasing large swarms of sterilized screwworm flies into the environment, cannot be quickly reinstated. Womack, who is also a veterinarian, expressed concern that ranchers in Texas may need to relearn the labor-intensive process of safeguarding their herds from this pest.

“There’s a generational ignorance – not stupidity, just ignorance,” Womack noted, referring to younger producers and veterinarians who lack experience with the screwworm. “Why would they?”

Read more: A Forgotten Parasite’s Return Threatens US Livestock: Dispatch

Screwworm flies lay their eggs in open wounds or membranes of warm-blooded animals. Once hatched, the larvae burrow into the flesh, using hook-like mouths to feed, which is how they earned their name. While they primarily target livestock and wild animals, they can also infest pets and even humans, leading to large, open wounds filled with maggots.

Although treatable, the challenge for ranchers lies in the need for meticulous herd inspections if the screwworm reestablishes itself in the U.S. This is particularly daunting in Texas, where ranches can span hundreds of acres and labor is often in short supply. Sick cattle tend to hide in dense brush, making them difficult to locate and treat.

The USDA estimates that an outbreak could cost Texas cattle producers $732 million and inflict a $1.8 billion hit to the state economy. Texas, known for its rich history of cattle ranching, still boasts the largest herd in the U.S., with 12.1 million head, accounting for about 14% of the total U.S. inventory.

The screwworm will likely remain a priority for years, even if it never infests American cattle, according to T.R. Lansford, deputy executive director of the Texas Animal Health Commission. This is partly due to the ongoing ban on imports from Mexico, a crucial source of feeder cattle, which has been largely halted since late 2024.

The ban was initiated after Mexican inspectors found screwworm in a cow at a checkpoint near the Guatemalan border. Concerns escalated in December 2025 when authorities discovered the parasite in a six-day-old calf in Tamaulipas, a Mexican state adjacent to Texas.

“This perks up my cowboy logic,” remarked Texas Agriculture Commissioner Sid Miller, noting that the calf was likely too young to have traveled from farther south, suggesting it was infested locally.

As of January 29, the USDA reported 20 cases in Tamaulipas, with eight still active. The screwworm, which took decades to eradicate, has made a comeback in less than five years.

“This was so effective, I never thought I would be working on screwworm,” said Phillip Kaufman, head of the Department of Entomology at Texas A&M University.

The methods for combating screwworms have not significantly changed since the 1960s. Scientists utilize radioactive carbon to sterilize screwworm flies, releasing them over infested areas. The sterile males mate with females, who reproduce only once, leading to a gradual decline in the population. Continuous releases are necessary to prevent resurgences.

Last week, as cases continued to rise in Tamaulipas, the USDA began releasing sterile flies along the Texas border. However, full-scale eradication requires a fly production capacity that the U.S. has lost and cannot rebuild for years. The eradication campaign once needed facilities capable of producing 500 million sterile flies weekly, but current global production is limited to a single facility in Panama, which can only manage 100 million.

In 1977, the USDA moved its screwworm research facility from southern Texas to Mexico. When the U.S. and Mexico dissolved their joint screwworm commission in 2012, the U.S. handed over the facility to Mexico, which subsequently shut it down as the threat diminished.

The international effort to eradicate screwworm had pushed the pest to the Darien Gap, a challenging jungle area on the Panama-Colombia border. However, a combination of pandemic-related disruptions at the sterile fly facility in Panama and changing grazing patterns are believed to have contributed to the new outbreak.

Officials are now focused on rebuilding production capacity in North America, starting with a $750 million investment to restart the Texas air base facility. The USDA aims to produce 100 million sterile flies weekly by spring 2027 and 300 million by 2029. Additionally, the U.S. has allocated $21 million to help retrofit a fruit-fly facility near the Guatemalan border for screwworm production by summer 2026.

“We desperately need those flies,” Kaufman emphasized.

Many Texas ranchers are also concerned about the potential impact on wildlife, such as deer and feral hogs, which contribute to revenue through hunting leases. Evidence of the screwworm’s devastating effects on wild animals already exists. In 2016, biologists found the flies in the Florida Keys, where they infested an endangered species of white-tailed deer. It took five months to eradicate the screwworm from the state, but during that time, 15% of the Key deer population perished.

“My biggest concern is how it will negatively impact the economics of rural America,” stated Donnell Brown, a fifth-generation Texas cattleman at R.A. Brown Ranch in Throckmorton, a 5,000-acre spread located about 160 miles west of Dallas.

Brown has never dealt with an infested cow, but he recalls the “rancid” tubes of white paste his father used for treatment. The odor was so overpowering that “there aren’t even words to describe it.” Now, he fears the screwworm’s return is imminent.

“My job is to take care of these animals,” he said, watching a mother cow lick her newborn calf. “I am very concerned that it’s not if, but when.”

Copyright 2026 Bloomberg.

Topics
Texas

Chris Womack stands as one of the few Texas ranchers who vividly recalls the battle against the New World screwworm, a pest that was once eradicated but is now threatening to return to the U.S. after reappearing in northern Mexico.

“You never forget the smell,” Womack, 60, reminisced about his first encounter with a calf infested with screwworm maggots. This was just one of many cases he and his father treated during the early 1970s when an outbreak devastated Texas ranchers. The screwworm parasite can kill cattle in less than two weeks, making it a formidable foe.

Now, over 50 years later, Womack and fellow Texas cattlemen are preparing for the potential resurgence of this pest. Reports of cases are increasing in a Mexican state bordering Texas, as the screwworm has escaped the containment efforts of an international eradication program that had kept it at bay for decades. In response, Texas Governor Greg Abbott issued a disaster declaration last week to mobilize state resources for the screwworm response.

The return of the screwworm could severely impact the $130 billion U.S. cattle industry, which is already grappling with a record-low herd and rising operational costs. The screwworm’s presence led to a ban on cattle imports from Mexico for much of the last 14 months, further straining American beef producers at a time when beef prices are at an all-time high, causing frustration among consumers facing rising food costs.

The eradication program, which relies on releasing large swarms of sterilized screwworm flies into the environment, cannot be quickly reinstated. Womack, who is also a veterinarian, expressed concern that ranchers in Texas may need to relearn the labor-intensive process of safeguarding their herds from this pest.

“There’s a generational ignorance – not stupidity, just ignorance,” Womack noted, referring to younger producers and veterinarians who lack experience with the screwworm. “Why would they?”

Read more: A Forgotten Parasite’s Return Threatens US Livestock: Dispatch

Screwworm flies lay their eggs in open wounds or membranes of warm-blooded animals. Once hatched, the larvae burrow into the flesh, using hook-like mouths to feed, which is how they earned their name. While they primarily target livestock and wild animals, they can also infest pets and even humans, leading to large, open wounds filled with maggots.

Although treatable, the challenge for ranchers lies in the need for meticulous herd inspections if the screwworm reestablishes itself in the U.S. This is particularly daunting in Texas, where ranches can span hundreds of acres and labor is often in short supply. Sick cattle tend to hide in dense brush, making them difficult to locate and treat.

The USDA estimates that an outbreak could cost Texas cattle producers $732 million and inflict a $1.8 billion hit to the state economy. Texas, known for its rich history of cattle ranching, still boasts the largest herd in the U.S., with 12.1 million head, accounting for about 14% of the total U.S. inventory.

The screwworm will likely remain a priority for years, even if it never infests American cattle, according to T.R. Lansford, deputy executive director of the Texas Animal Health Commission. This is partly due to the ongoing ban on imports from Mexico, a crucial source of feeder cattle, which has been largely halted since late 2024.

The ban was initiated after Mexican inspectors found screwworm in a cow at a checkpoint near the Guatemalan border. Concerns escalated in December 2025 when authorities discovered the parasite in a six-day-old calf in Tamaulipas, a Mexican state adjacent to Texas.

“This perks up my cowboy logic,” remarked Texas Agriculture Commissioner Sid Miller, noting that the calf was likely too young to have traveled from farther south, suggesting it was infested locally.

As of January 29, the USDA reported 20 cases in Tamaulipas, with eight still active. The screwworm, which took decades to eradicate, has made a comeback in less than five years.

“This was so effective, I never thought I would be working on screwworm,” said Phillip Kaufman, head of the Department of Entomology at Texas A&M University.

The methods for combating screwworms have not significantly changed since the 1960s. Scientists utilize radioactive carbon to sterilize screwworm flies, releasing them over infested areas. The sterile males mate with females, who reproduce only once, leading to a gradual decline in the population. Continuous releases are necessary to prevent resurgences.

Last week, as cases continued to rise in Tamaulipas, the USDA began releasing sterile flies along the Texas border. However, full-scale eradication requires a fly production capacity that the U.S. has lost and cannot rebuild for years. The eradication campaign once needed facilities capable of producing 500 million sterile flies weekly, but current global production is limited to a single facility in Panama, which can only manage 100 million.

In 1977, the USDA moved its screwworm research facility from southern Texas to Mexico. When the U.S. and Mexico dissolved their joint screwworm commission in 2012, the U.S. handed over the facility to Mexico, which subsequently shut it down as the threat diminished.

The international effort to eradicate screwworm had pushed the pest to the Darien Gap, a challenging jungle area on the Panama-Colombia border. However, a combination of pandemic-related disruptions at the sterile fly facility in Panama and changing grazing patterns are believed to have contributed to the new outbreak.

Officials are now focused on rebuilding production capacity in North America, starting with a $750 million investment to restart the Texas air base facility. The USDA aims to produce 100 million sterile flies weekly by spring 2027 and 300 million by 2029. Additionally, the U.S. has allocated $21 million to help retrofit a fruit-fly facility near the Guatemalan border for screwworm production by summer 2026.

“We desperately need those flies,” Kaufman emphasized.

Many Texas ranchers are also concerned about the potential impact on wildlife, such as deer and feral hogs, which contribute to revenue through hunting leases. Evidence of the screwworm’s devastating effects on wild animals already exists. In 2016, biologists found the flies in the Florida Keys, where they infested an endangered species of white-tailed deer. It took five months to eradicate the screwworm from the state, but during that time, 15% of the Key deer population perished.

“My biggest concern is how it will negatively impact the economics of rural America,” stated Donnell Brown, a fifth-generation Texas cattleman at R.A. Brown Ranch in Throckmorton, a 5,000-acre spread located about 160 miles west of Dallas.

Brown has never dealt with an infested cow, but he recalls the “rancid” tubes of white paste his father used for treatment. The odor was so overpowering that “there aren’t even words to describe it.” Now, he fears the screwworm’s return is imminent.

“My job is to take care of these animals,” he said, watching a mother cow lick her newborn calf. “I am very concerned that it’s not if, but when.”

Copyright 2026 Bloomberg.

Topics
Texas