The New World screwworm resurfaced in New Mexico just as a major gateway for Mexican cattle imports is poised to open in the state. 

The parasite, which infests the wounds of livestock, was confirmed on September 17 in a horse in New Mexico’s Grant County, according to the U.S. Department of Agriculture. Earlier that same day, Agriculture Secretary Brooke Rollins had announced plans to reopen the country’s largest port for Mexican cattle — situated roughly 150 miles from the new case.

The decision to open the port in Santa Teresa is part of the U.S.’s effort to amp up a trade that had been paused to prevent the spread of the screwworm, and comes as cases of the deadly parasite have been largely contained since the outbreak began in early June. There have been 50 cases of the screwworm in the U.S., almost all in Texas, with only three currently active. Nearly 2,000 cases remain active in Mexico.

Rollins acknowledged that screwworm has not yet been eradicated, but was confident in the protocols that the USDA has put in place. She said on September 17 at a press conference announcing the port reopening that the agency will delay the move if “we’re not 100% sure in the safety and the protocols.”

The USDA said in a post on X that the port is still scheduled to reopen on September 24 as planned. The agency has established a quarantine zone, is deploying sterile flies to curb potential spread and is expanding wildlife surveillance, according to the post.

The source of the infestation is still under investigation, as the horse hadn’t moved from the region recently, the Santa Fe New Mexican reported, citing state veterinarian Samantha Holeck. A spokesperson for the New Mexico Department of Agriculture said it has no additional information beyond confirming the case.

Tom Paterson, president of the New Mexico Cattle Growers Association, said there is “no relationship between port normalcy and screwworm in a horse.” Still, it is a reminder that ranchers have “got to be diligent” in inspecting their animals.

The Santa Teresa port is scheduled to open on September 24. It is the second port-of-entry in the U.S. to accept Mexican live cattle. Nearly 500,000 cattle were shipped through Santa Teresa in 2024, amounting to about 40% of the U.S.’s total imports from Mexico, according to the USDA.

Live cattle from Mexico is expected to provide a reprieve to the U.S.’s severe cattle shortage, which has tightened availability for meatpackers and sent consumer beef prices surging. The number of animals placed in feedlots to gain weight before being sent to slaughter in August was down 9% from the prior year, the lowest for that time of year in data going back 30 years, according to the USDA.

Rollins also said the agency is also looking at reopening a port in Columbus, New Mexico, assuming “that we can continue to show that we have contained” the pest. 

The case is the second in New Mexico, the only state outside of Texas where the screwworm has been found. A dog in Lea County was among the first confirmed cases in June. The pet recovered, but questions remained at the time as to whether it had contracted the parasite locally or in Mexico.