Mexico refuses to yield to US demands on screwworm livestock response

On Sunday 27 April 2025, Mexican Secretary of Agriculture and Rural Development Julio Berdegué posted a strong response on X to a letter sent the previous day by US Agriculture Secretary Brooke Rollins.

Berdegué rejected Rollins pressure for greater US control over Mexico’s response to the New World Screwworm outbreak, asserting that Mexico would not “subordinate” itself to US directives.

In her letter, Rollins demanded that Mexico lift restrictions on USDA contractor planes and waive customs duties on crucial eradication equipment.

She warned that:

Every delay in granting full operational authority and eliminating customs barriers undermines our collective ability to carry out this emergency response.”

Rollins also set a deadline for Mexico to act, threatening to reimpose restrictions on live cattle, bison and equine imports if the issues were not resolved by Wednesday 30 April, in order to “protect the interest of the agriculture industry in the United States.”

Berdegué quickly addressed the demands in a public post on X, stating:

I have promptly responded to the letter from the United States Agriculture Secretary Brooke Rollins regarding the issue of the cattle screwworm. As our president, Claudia Sheinbaum, has said, we act with a cool head; we collaborate, cooperate, but we never subordinate ourselves.”

He did not reveal the details of his reply but did express confidence about reaching favourable agreements.

The screwworm outbreak has already hit Mexican cattle exports hard, with US imports falling sharply. Once the US’ largest supplier of cattle alongside Canada, USDA data reveals that Mexico exported just 24,000 head of cattle to the US last month, down from 114,000 a year earlier.

A previous import ban, triggered by the pest’s discovery in late 2024, was lifted in February following the introduction of more stringent animal health protocols. However, the ongoing risk remains high, and tensions between the two countries are mounting.

What is New World Screwworm?

New World Screwworm (Cochliomyia hominivorax) is a parasitic fly that poses a severe threat to livestock, wildlife and even humans. Maggots from screwworm flies burrow into the skin of living animals, causing devastating infections that can lead to death if untreated. The fly has a significant economic impact, particularly on the livestock industry, as it destroys animals’ health and productivity.

Once eradicated from both the US and Mexico through decades of costly and coordinated sterile insect programmes, the pest’s resurgence is a serious concern.

Its re-emergence in southern Mexico threatens to spread northward, potentially wreaking havoc on US livestock and costing the agricultural industry billions in losses. The outbreak is particularly urgent because of the rapid pace at which the screwworm can spread if not contained.

But with US-Mexico trade relations already strained by new tariffs and wider global tensions, the screwworm crisis risks deepening the agricultural and economic fallout on both sides of the border.