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New World Screwworm Found in New Mexico Horse as USDA Prepares to Reopen Livestock Port
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New World Screwworm Detected in New Mexico Horse Ahead of Port Reopening
On September 17, U.S. officials confirmed a case of New World screwworm in a horse from Grant County, New Mexico, near the Mexican border. The infestation marks the state’s second confirmed case since the parasite entered the United States from Mexico in June. The discovery came just days before Agriculture Secretary Brooke Rollins announced that the Santa Teresa port of entry would reopen to Mexican livestock on September 24.
Background & Context
The New World screwworm, a flesh-eating fly larva, was declared eradicated in the United States in the 1960s. An outbreak began in June 2024 when the parasite crossed the border from Mexico, prompting a halt to livestock imports. Trade resumed in August 2024 through the Douglas, Arizona port as part of a phased reopening plan. USDA’s Animal and Plant Health Inspection Service (APHIS) lifted New Mexico’s screwworm-infested zone after the state’s only prior case—a dog confirmed on June 7—was cleared.
Data & Statistics
- USDA’s dashboard lists 50 confirmed U.S. screwworm cases since the June outbreak, with three active cases.
- Active cases include two horses (New Mexico, Texas) and a dog in Texas.
- The CDC rates the risk of human infection as “very low.”
- Texas experts estimate a statewide outbreak could cost up to US $1.8 billion.
Official Statements & Responses
- Jenny Green, spokesperson for the New Mexico Department of Agriculture, said the horse case had not been confirmed at the time of the September 24 news conference and offered no update on the reopening schedule.
- The CDC reiterated that human risk remains minimal and that no human screwworm cases have been reported.
- The U.S. Equestrian Federation urged horse owners to inspect animals daily for wounds, swelling, foul odors, or maggots and to contact veterinarians promptly.
On-the-Ground Reports
Border officials have observed ongoing smuggling of horses and other livestock that bypass veterinary inspections. In Florida, veterinarians warn that the state’s climate could support the parasite year-round, stating, “It would make sense that it would get to Florida at some point.” At Mill Creek Farm, a nonprofit retirement home for horses, president Paul Gregory said staff are now checking fence lines for any source of blood, noting, “If there’s any blood, that’s where the screwworm can come in.”
Conflicting Reports & Gaps
- The usnews article reported that the horse case had not been confirmed at the time of Rollins’s September 24 conference, while TheHill piece states the infection was confirmed before the announcement. USDA has not clarified the timing.
- No official source has linked any of the 48 confirmed U.S. cases to smuggled animals, though investigators suggest the true number may be undercounted.
Verbatim Quotes
- “It would make sense that it would get to Florida at some point,” — Sally DeNotta, UF veterinarian
- “We’re getting ready to reopen that New Mexico port next week,” — Brooke Rollins, Agriculture Secretary
What’s Next
USDA officials indicated that the September 24 reopening of the Santa Teresa port will proceed unless a new screwworm threat emerges. The phased plan calls for additional New Mexico ports to follow the Arizona reopening, with flexibility to pause or adjust the schedule based on surveillance data. A USDA facility in Texas is slated to begin producing sterile flies in early 2027, a key component of the long-term eradication strategy.