US, Mexico Reach Agreement to Combat Cattle-Infesting Fly

U.S. cattle producers warned that failure to control the outbreak could devastate the domestic beef industry.

Cattle are brought through a gate in the border fence from Mexico into the United States at the Santa Teresa International Export/Import livestock crossing in Santa Teresa, N.M., on June 5, 2019. Joe Raedle/Getty Images

The United States and Mexico have reached an agreement to bolster joint efforts to combat an outbreak of New World screwworm, a parasitic fly that infests and feeds on the flesh of living animals.

“Mexico has agreed to let our sterile fly planes land,” U.S. Agriculture Secretary Brooke Rollins announced Tuesday on social media platform X, days after warning against burdensome customs duties imposed by Mexico on American aviation equipment she said is critical to eradicating the pest.

The Epoch Times has reached out to the U.S. Department of Agriculture (USDA) for more details about the agreement.

New World screwworm flies lay eggs in open wounds of warm-blooded animals. When the larvae hatch, they burrow into the host’s flesh, causing severe tissue damage that can be fatal if untreated. While primarily a threat to livestock and wildlife, screwworms can also infest humans in very rare cases.

The United States eradicated New World screwworm domestically in 1966 using the sterile insect technique—a process in which millions of sterilized male flies are released into the wild to mate with females, effectively collapsing their population. However, the parasite remains endemic to parts of South America and the Caribbean.

The current outbreak began in 2022 and has steadily spread northward through Panama, Costa Rica, Nicaragua, Honduras, and Guatemala. It reached Mexico in 2024, prompting the USDA to allocate $165 million in emergency funding to stop the pest’s advance toward the U.S. border.

On Saturday, Rollins revealed on X that she had sent a letter to Mexican Agriculture Minister Julio Berdegué, warning that the United States would suspend livestock imports from Mexico starting April 30 unless the country took additional steps to help contain the outbreak.

Specifically, she demanded that Mexico waive restrictions and fees on U.S. eradication equipment, including USDA-operated sterile fly planes.

“As the New World screwworm outbreak is escalating, Mexico must eliminate restrictions on USDA aircraft and waive customs duties on eradication equipment,” she said. “These barriers critically impair our joint response.”

She also requested a one-year operating permit for Dynamic Aviation, a USDA-contracted company conducting aerial missions to fight the outbreak. The company is currently restricted to 60-day permits and limited to flying six days a week.

“The success of the operation requires consistent flights seven days per week, including direct flight permissions, pilot credentialing, facility access, and full control over their logistical and technical operations,” Rollins told her Mexican counterpart.

Under the Biden administration, Mexican cattle imports were blocked in late November 2024. The Trump administration maintained the ban into February, and Rollins had warned that the suspension could be reinstated if Mexico failed to cooperate with pest control efforts. The United States typically imports more than 1 million head of cattle from Mexico each year.

The National Cattlemen’s Beef Association, a trade group representing more than 175,000 cattle producers, warned that failure to control the outbreak could devastate the domestic industry.

“Screwworm is very destructive and could cost American producers millions of dollars a year if it reaches us,” said Buck Wehrbein, the association’s president and a Nebraska cattleman.

Although screwworm is considered eradicated in the United States, the USDA says that continued efforts are necessary to preserve that status. The agency has long maintained a biological barrier at the Darién Gap, a narrow, jungle-covered land bridge connecting Panama and Colombia, where it works with Panama to release up to 20 million sterile flies each week to prevent the pest’s northward spread.

Human infection of screwworm flies is called myiasis. According to the U.S. Centers for Disease Control and Prevention, people who travel to affected countries in South America and the Caribbean, spend time around livestock, sleep outdoors, and have open wounds are at greater risk of infestation.

Earlier this month, Mexico confirmed its first human case of screwworm-related myiasis. The patient was a 77-year-old woman in Chiapas, Mexico’s southernmost state bordering Guatemala.