USDA has requested adjustments to Mexican facilities set up to screen cattle exports to the U.S. for the New World Screwworm, Agriculture Secretary Tom Vilsack told his Mexican counterpart in a letter in which he also called for additional steps to curb the parasite's spread in the region.

The U.S. suspended imports of certain Mexican livestock in November after flesh-eating screwworm fly larvae was detected in the south of the country. The two governments reached a technical agreement in December on the protocol for resuming cross-border livestock trade, which included the establishment of USDA-approved holding pens where inspectors can review and treat Mexican cattle destined for the U.S.

In a letter Friday to Mexico’s Agriculture Secretary Julio Antonio Berdegué obtained by Agri-Pulse, Vilsack said the first inspections of the pre-export detection facilities occurred last week.

“To support in finalizing this work, I urge you to encourage the needed modifications be made expeditiously to the facilities so that my teams can grant full approval as soon as possible,” Vilsack told his Mexican counterpart.

These facility approvals, he added, represent a “key final step” in implementing the protocol for resuming livestock exports.

The import suspension disrupted a growing cross-border livestock trade. The U.S. imported more than 1.2 million heads of cattle from Mexico in 2023, according to an analysis by Derrell Peel at Oklahoma State University. That is the largest volume since 2020.

The restrictions also came amidst the peak import season. In prior years, December had been the busiest import month, with11% of annual U.S. cattle imports from Mexico arriving during the month on average.

Between the 1960s and early 2000s, USDA and other Central American governments successfully eradicated screwworm in the region by releasing sterile flies to mate with fertile females. The effort reduced and, eventually, eliminated the fly population from everywhere north of Panama’s Darien Gap – the narrow isthmus connecting South to Central America.

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But in recent years, the flies have been moving northwards again, with cases detected in countries throughout the region – including an outbreak in and around the Florida Keys in 2016 and 2017.

In his letter to Berdegué, Vilsack also asked the Mexican government to strengthen existing efforts to halt the flies’ northward incursion by establishing two planned sterile fly dispersal centers in the south of the country.

“This strategic step is critical to our future successful efforts,” Vilsack argued.

The sterile fly dispersion effort, Vilsack said, has helped prevent NWS’ northward spread in the seven weeks since it was detected in Mexico.

“The emergency funding that I have authorized has allowed us to increase sterile fly production fivefold in the past year and enhance our regional response to NWS,” Vilsack added, thanking the Mexican secretary for his support for the “shared goal” of driving the fly population back to Panama’s Darien Gap.

“I hope you will join me in supporting our teams to complete these remaining key steps as soon as possible to reach a new phase in our fight against NWS while resuming strong trade in Mexican cattle to the United States,” he concluded.