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 Thursday in a horse in New Mexico’s Grant County, according to the US 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 US’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 US, 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 Thursday 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.” But that’s unlikely to happen based on the new case, the Santa Fe New Mexican reported, citing state veterinarian Samantha Holeck. She said the source of the infestation is still under investigation, as the horse hadn’t moved from the region recently.

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