The US Department of Agriculture (USDA) has suspended live cattle, horse, and bison imports through US ports of entry along the southern border due to the continued and rapid northward spread of the potentially devastating pest, New World Screwworm (NWS), in Mexico.

NWS has been recently detected in remote farms with minimal cattle movement as far north as Oaxaca and Veracruz, about 700 miles from the US border. This has prompted government intervention to close the borders to cattle imports just a few months after they were resumed.

In a USDA announcement over the weekend, the agency stressed that despite efforts to contain the spread, both the US and Mexico are continuing their efforts to eradicate NWS in Mexico and “work in good faith” together. 

“However, despite these efforts and the economic impact on both countries due to this 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,” it says.

Mexico’s agricultural officials disagree with the new border closure measure and are hoping that a deal can be reached to resume trade.

The USDA Animal Plant Health Inspection Service and Customs and Border Protection have already begun restricting the importation of live animal commodities originating from, or transiting Mexico. 

The suspension will remain in place month-by-month as US officials work with Mexico to contain the damaging pest and prevent the sort of crisis which hit the US livestock industry several decades ago with devastating impacts.

The USDA will review Mexico’s latest data and metrics in two weeks.

“It is my duty to take all steps within my control to protect the livestock industry in the US from this devastating pest,” says Secretary of Agriculture Brooke L. Rollins. “The protection of our animals and safety of our nation’s food supply is a national security issue of the utmost importance.”

“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.”

Effective eradication

Eliminating the pest requires robust active field surveillance with education and outreach to ensure prevention, treatment, and early detection; controlled animal movement to limit spread; and sustained sterile insect dispersal, notes the USDA.

Suspending livestock transport through southern ports of entry will assist in the effort to limit northbound transport of NWS through livestock commerce, and will allow the US to reassess whether current mitigation standards remain sufficient.

Officials also stress that the northward spread of NWS is possible through natural wildlife movements, including wildlife that transit the border region without impediment.