After closing southern border crossings to livestock in May to help stop the spread of New World Screwworm, the U.S. Department of Agriculture began an incremental “risk-based” reopening Monday that will allow horses to cross the border. The decision comes as USDA officials say the northward spread of the pest has stopped in the past two months and efforts to stop fly spread are ramping up.

“Progress has been made in several critical areas since the ports were closed on May 11^th, including: resolution of challenges with conducting flights in Mexico that has allowed our team to consistently conduct sterile NWS fly dispersal seven days each week and dispersal of more than 100 million flies each week,” the USDA stated in a June 30 press release. “We also sent five teams of APHIS staff to visit/observe and gain a deeper understanding of Mexico’s NWS response and allow us the opportunity to share our feedback. We have not seen a notable increase in reported NWS cases in Mexico, nor any northward movement of NWS over the past eight weeks.”

New World Screwworm is a fly larvae foreign to the United States which burrow into the flesh of living animals, causing serious and potentially deadly damage. Screwworm is endemic in Cuba, Haiti, the Dominican Republic and countries in South America. The United States and Panama have collaborated through the Commission for the Eradication and Prevention of Screwworm to prevent the pest’s northward movement by using sterilized insects to eradicate screwworm fly populations. The approach eradicated NWS from the United States in 1966 and eliminated a small outbreak from the Florida Keys in 2017. 

The U.S. is contributing $21 million toward a Mexican facility that will produces the sterile flies—construction of which is now underway, Mexican officials said Monday, as well as $8.5 million to build a facility this year at Moore Air Base in Texas, from which the sterile flies can be dropped from airplanes to help stop screwworm spread.

A port in Douglas, Arizona, near Sonora, Mexico, was scheduled to reopen Monday to equine, cattle and bison crossings. That port was chosen as the first to reopen because it “presents the lowest risk based upon the geography of Sonora and a long history of effective collaboration between [the USDA Animal and Plant Health Inspection Service] and Sonora on animal health issues,” according to the June 30 press release. 

USDA has set a timeline for reopening two more ports at weekly intervals after that—Columbus, New Mexico, on July 14 and Santa Teresa, New Mexico on July 21—but will re-evaluate after each port reopens to ensure no adverse effects arise, the press release said. If all goes well, two more Texas ports would reopen in the following months: Del Rio on Aug. 18 and Laredo on Sept. 15. The Santa Teresa, New Mexico, port has equine quarantine facilities on the U.S. side of the border that will be available when that port is reopened.

While cattle and bison imports will be restricted to animals raised in certain parts of Mexico, horses from any part of the country will be allowed across the border. However, horses must quarantine for seven days at the port of entry and must import in accordance with USDA’s equine screwworm protocol. 

For more information on the border reopening, visit the USDA website. 

For more information about screwworm and how to protect your horses, click here.