U.S. Halts Livestock Imports From Mexico Again. Here Is The Reason Why

The USDA has announced the launch an $8.5 million sterile fly dispersal facility in South Texas. It's anticipated to begin producing sterile male flies by the end of the year

NOTE: this article was originally published to Houston Chronicle's Apple News channel on July 11, 2025.. It was written by Sondra Hernandez.

The U.S. has again halted livestock imports from Mexico after the parasitic New World screwworm fly closer to the border. 

Earlier this week, Mexico’s national agriculture department reported a new case of New World Screwworm in Veracruz state, according to a statement from the U.S. Department of Agriculture. That puts the fly just 370 miles south of the U.S. border and about 160 miles further north than its previous reach.

What is the latest?

In May, the U.S. announced it would close its border with Mexico to imports of live cattle, horses and bison. By June 30, three ports of entry were to open in a risk-based strategy and another two were to open by Sept. 15. 

Since then, the fly has been reported 185 miles northeast of Mexico City, fewer than 400 miles from the Texas border. 

“The United States has promised to be vigilant — and after detecting this new NWS case, we are pausing the planned port reopenings to further quarantine and target this deadly pest in Mexico,"  said U.S. Secretary of Agriculture Brooke L. Rollins in a statement. "We must see additional progress combating NWS in Veracruz and other nearby Mexican states in order to reopen livestock ports along the Southern border."

What is the New World screwworm fly? 

New World screwworm, often called NWS, is a species of parasitic worm that can feed on live tissue and cause the parasitic infection myiasis, according to the U.S. Centers for Disease Control and Prevention. 

NWS is rare in the U.S. and is most commonly found in South America and the Caribbean, according to the CDC. 

Though it primarily affects livestock, those who travel to and are around livestock in rural areas of South America and the Caribbean can contract NWS, the CDC warns.  

Can humans contract New World screwworm myiasis?

Yes, in rare cases, humans can contract New World screwworm myiasis if the insect lays eggs in an open wound, according to the CDC. 

To treat the disease, healthcare providers must remove the larvae, sometimes through surgery, according to the CDC. 

Does the New World screwworm have a history in Texas? 

Though NWS has been present in the U.S. since 1842, it was first named as a significant problem in the southeast U.S. in 1933, according to the USDA.

USDA eradicated NWS from the U.S. in the 1960s, USDA and its partners contained it to South America using sterile insect technology; however, NWS began spreading northward and was detected in southern Mexico in November 2024, according to information from the USDA.

What is being done to combat NWS?

In June, Rollins announced a plan to combat the spread of the parasite by aggressive protection of the border, increasing eradication efforts in Mexico and increasing readiness in the U.S. 

Additionally, the USDA has announced the launch an $8.5 million sterile fly dispersal facility in South Texas. It's anticipated to begin producing sterile male flies by the end of the year, as reported by USA Today.