Screwworm threat forces US to halt cattle imports from Mexico: What to know

WASHINGTON - The U.S. said it has suspended imports of live cattle from Mexico amid the threat of a flesh-eating maggot known as the New World screwworm (NWS).

The U.S. Department of Agriculture announced the move on Sunday, saying the order includes live cattle, horse, and bison imports through U.S. ports of entry along the southern border "due to the continued and rapid northward spread."

Here’s what to know:

New World screwworm threat

What we know:

The U.S. will suspend the imports of live cattle from Mexico for 15 days to review the joint strategy in the fight against the screwworm, according to Mexico’s Agriculture Secretary Julio Berdegué. Berdegué said on the social platform X that he had spoken with his U.S. counterpart, Brooke Rollins, who had informed him of the decision.

"We don’t agree with this measure, but we’re confident we’ll reach an agreement sooner rather than later," Berdegué said.

For its part, the USDA said despite efforts to eradicate the screwworm, as well as the economic impact on both countries due to such action, "there has been unacceptable northward advancement of NWS and additional action must be taken to slow the northern progression of this deadly parasitic fly."

Dig deeper:

The New World screwworm is a type of maggot known for its feeding behavior, using its sharp mouth hooks to burrow into a wound, "feeding as they go like a screw being driven into wood," according to the USDA’s Animal and Plant Health Inspection Service (APHIS). These pests can cause fatal wounds to livestock, birds, wildlife, pets and, in rare cases, humans. 

"When NWS fly larvae (maggots) burrow into the flesh of a living animal, they cause serious, often deadly damage to the animal," according to the USDA’s statement on Sunday. 

The backstory:

New World screwworms were nearly eradicated in the U.S. in 1966 using the sterile insect technique, according to FOX Weather. But since 2023, cases have been rising in Central America and Mexico, causing concern that the maggots could return to America.

The U.S. restricted Mexican cattle shipments in late November 2024 following the detection of the pest, but lifted the ban in February after protocols were put in place to evaluate the animals prior to entry into the country.

But due to the screwworm’s rapid spread, the USDA issued its most recent halt to cattle imports from Mexico.

What they're saying:

"The United States has ordered the suspension of livestock imports through ports of entry along our southern border after the continued spread of the New World Screwworm in Mexico. Secretary Berdegué and I have worked closely on the NWS response; however, it is my duty to take all steps within my control to protect the livestock industry in the United States from this devastating pest," Rollins said in a statement. "The protection of our animals and safety of our nation’s food supply is a national security issue of the utmost importance." 

Rollins added: "Once we see increased surveillance and eradication efforts, and the positive results of those actions, we remain committed to opening the border for livestock trade. This is not about politics or punishment of Mexico, rather it is about food and animal safety."