WASHINGTON, D.C. – Due to the continued and rapid northward spread of New World Screwworm (NWS) in Mexico, USDA Secretary Brooke Rollins announced May 12 the suspension of live cattle, bison and horse imports through U.S. ports of entry along the southern border.

The USDA’s decision came in the wake of NWS recently being detected as far north as Oaxaca and Veracruz (Mexico), about 700 miles away from the U.S. border, in remote farms with minimal cattle movement, the agency said. Despite ongoing efforts between the U.S. and Mexico to eradicate the pest, the continued northward spread of NWS has prompted additional action, the agency added.

NWS is a parasitic fly whose larvae feed on the living tissue of warm-blooded animals, causing painful, infected wounds; adult flies are slightly larger than houseflies, with metallic blue/green bodies, orange eyes, and three dark stripes on their backs, according to Tennessee State Veterinarian Samantha Beaty, DVM.

To slow the northern progression of NWS, effective immediately, the USDA’s Animal Plant Health Inspection Service (APHIS), in conjunction with U.S. Customs and Border Protection, will restrict the importation of live animal commodities originating from, or passing through to Mexico, the agency said. This import suspension will be evaluated on a month-by-month basis, continuing until significant containment progress is achieved.

The USDA added that livestock currently being held for entry into the U.S. will still undergo the usual APHIS inspections and treatments to ensure they are not carrying NWS.

Rollins said she and Julio Berdegué Sacristán, Mexico’s secretary of agriculture and rural development, 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.

 “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,” Rollins said.

The USDA said effective eradication requires 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. Suspending livestock imports will assist in limiting the spread of NWS, while allowing the U.S. to reassess current mitigation standards. The northward spread of NWS is also possible through natural wildlife movements, the agency added.

Colin Woodall, National Cattlemen’s Beef Association (NCBA) CEO, said in a May 11 media statement, “The USDA’s border closure was entirely avoidable. U.S. government officials, NCBA and leaders from affiliated state cattle industry associations have been sounding the alarm for months. Unfortunately, the Mexican government created unnecessary bureaucratic hurdles, which rendered prevention efforts ineffective and allowed screwworm cases to spread unchecked beyond control points in southern Mexico.”

According to the USDA, the first case of NWS in Mexico was reported to the U.S. last November. After a positive detection of NWS in southern Mexico that same month, the USDA shut down the border for live animal trade. In February, the USDA said it resumed imports after APHIS and Mexico agreed to and implemented a comprehensive preclearance inspection and treatment protocol to ensure safe movement and steps to mitigate the threat of NWS.

Over the last two years, NWS has spread north throughout Panama and into Costa Rica, Nicaragua, Honduras, Guatemala, El Salvador, Belize, and now Mexico, the agency added.

Grant Dewell, Iowa State University beef extension veterinarian, told Farm World, “It is troubling in that last fall, the belief was that it was a single incursion (invasion or an attack) found during routine inspection near the Mexico-Guatemala border. The U.S. closed the border until we strengthened important requirements for cattle coming from Mexico, including enhanced inspections and treatment of livestock could be implemented.

“Now, six months after the first identification in Mexico and a couple of months of resumed trade, they are now finding the New World screwworm 300-plus miles north of Guatemala well into Mexico,” he said.

“This could indicate that either the infestation was a lot more than they initially thought, or that they are unable to stop the spread within the country,” he added. “Regardless, until Mexico can demonstrate that they have contained New World screwworm, I would not expect the routine importation of livestock from Mexico.”

Andrew P. Griffith, University of Tennessee professor of agricultural and resource economics, told Farm World, “There are several thought processes as it relates to this announcement. The first is how it impacts the domestic calf and feeder cattle market.

“In reality, the quantity of cattle crossing the border and coming north the past couple of months is only about 60 percent of what would typically be coming into the U.S. market,” he said. “This immediate closure, and not knowing how long it may last, should support prices for calves and feeder cattle as producers in the southern-feeding region will be needing cattle.

“The second thought is: how much of this is due to the threat of the New World screwworm and how much of it is to put pressure on the Mexican government to achieve alternative objectives?” he added. “I am not willing to say or not say that is what is going on, but this immediate closure could be serving multiple agendas.”

In the meantime, Dewell said, “We will probably lose all exports of live animals out of the U.S., at least in the short-term until containment can be established. The USDA would then begin releasing sterile male flies (in Southern Mexico and other areas throughout Central America, according to the USDA) to stop reproduction of the fly, but that will take a year or more, depending on the extent of infestation until they can have it contained and eradicated again.”

On May 14, NCBA joined affiliate state associations to urge Congress to pass the Strengthening Tactics to Obstruct the Population of Screwworms (STOP Screwworms) Act – introduced by U.S. Rep. Tony Gonzales (R-Texas) and U.S. Sen. John Cornyn (R-Texas) – to fund the opening of a new sterile fly facility in the United States.

Currently, the only such facility still active is in Panama, but it can’t produce enough sterile flies to fully prevent NWS from spreading to America’s southern border, NCBA said.

For more information on NWS-affected regions, visit the USDA’s APHIS Animal Health Status of Regions website at: www.aphis.usda.gov/regionalization-evaluation-services/region-health-status.