A working ranch horse in Presidio County, Texas, is the first equine case of New World screwworm in the current U.S. outbreak. US Equestrian said the larvae were found in a wound on one of the horse's hind limbs.
On Sept. 9, the Texas Animal Health Commission issued an order creating an infested zone in parts of Presidio and Jeff Davis counties because of the horse detection. Warm-blooded animals inside the zone, including horses, cattle, goats, dogs, and cats, cannot be moved out without prior authorization from the commission, an inspection, and any required treatment.
For horse owners, the case changes into a practical question. Earlier U.S. detections were mostly in cattle, along with goats and a dog, and the horse case shows the parasite is not only a cattle problem. Daily wound checks, fly control, and travel paperwork now matter for trail riders, ranch families, and anyone hauling horses out of far West Texas.
A Horse Case Arrives While Other Zones Are Lifted
According to a Texas Public Radio tracker built on USDA data, the U.S. count stood at 49 confirmed cases as of Sept. 9, including 48 in Texas, with four still active. USDA considers a case active while treatment and wound management of the infested animal are still underway.
At the same time, Texas has been lifting earlier restrictions. The commission released zones in parts of Gillespie, Kerr, Kimble, La Salle, and Webb counties on Aug. 31, then released zones covering parts of Coke, Tom Green, Uvalde, and Zavala counties on Sept. 3.
Presidio County was not new to restrictions. A July 30 order had already covered parts of Brewster and Presidio counties. The new order, which designates Infested Zone 21, extends restrictions into part of Jeff Davis County, home to the town of Fort Davis. Because the order covers only parts of each county, owners should check the commission's zone map for exact boundaries.
Agriculture Secretary Brooke Rollins has said federal officials are making progress but that the threat has not passed, pointing to Arizona and New Mexico as areas of concern. "We're not out of the woods yet," Rollins said, according to Texas Public Radio.
Horse Owners Face New Checks Before Hauling
For households with horses, the most immediate effect is on movement. Under the commission's orders, any warm-blooded animal leaving an infested zone must be inspected by the commission or a certified inspector, who completes a movement and treatment certificate listing the product used and the animal's official identification. That certificate must travel with the animal. The commission also links to an online guide to animal movement requirements for owners sorting out their specific situation.
Outside the zones, the risk is lower but not zero. US Equestrian said its protocols for licensed competitions may include checking horses for wounds when they arrive. The federation also noted that state animal health officials set entry rules for animals coming from states or zones with cases, so owners heading to rodeos, sales, or trail events should confirm requirements before loading a trailer.
The federation urged owners to inspect horses every day for wounds, swelling, drainage, foul odor, or maggots. It asked owners to pay close attention to small cuts, surgical sites, the navel area of foals, and moist areas around the lips, nostrils, eyes, and genitals, and said "Even small cuts or sores should be cleaned, protected, and checked closely."
The FDA has also issued an emergency authorization for an ivermectin product for horses. The product, Ivermectin Liquid for Horses, is available only by prescription from a licensed veterinarian and is authorized for short-term prevention when given within 24 hours of birth or at the time of initial wound care. It is not authorized to treat an existing infestation.
Human Risk Stays Very Low, but Open Wounds Deserve Attention
The CDC says the current public risk is very low and that no locally acquired human infestations have been reported in the United States. Since the parasite reemerged in Central America and Mexico, the only U.S. human case the CDC has reported was confirmed in August 2025 in a person who had traveled to El Salvador.
Screwworm flies lay eggs in open wounds or body openings, and the larvae feed on living tissue. People who spend time outdoors in affected counties, including hunters, ranch workers, and hikers, should keep cuts clean and covered. Anyone who sees or feels maggots in a wound should contact a health care provider right away and should not try to remove them alone. The Texas Department of State Health Services handles information on human infestations.
USDA has said screwworm is not a food safety threat, and inspection systems are designed to keep infested animals out of the food supply.
Key Dates in the West Texas Response
Sept. 9, 2026: The commission issues an order creating an infested zone in parts of Presidio and Jeff Davis counties after screwworm is detected in a Presidio County ranch horse.
Sept. 3 to 4, 2026: Texas releases zones in parts of Coke, Tom Green, Uvalde, and Zavala counties and issues a modified release order for Kimble, Schleicher, and Sutton counties.
Aug. 31, 2026: The first zone releases take effect in parts of Gillespie, Kerr, Kimble, La Salle, and Webb counties.
July 30, 2026: An order establishes a zone covering parts of Brewster and Presidio counties.
June 3, 2026: USDA confirms the first U.S. animal case of the outbreak, a calf in Zavala County.
Several questions remain open. Officials have not said publicly how the horse was exposed or whether nearby animals were affected. The new zone will stay in place until the commission releases it, and USDA updates its public dashboard as cases are confirmed or closed.
Suspected cases in Texas animals should be reported to a commission region office or to the commission's veterinarian-on-call line at 1-800-550-8242. The steps that protect animals are simple: find wounds early, treat them, and call a veterinarian at the first sign of larvae.
Key Questions Answered
What happened? A working ranch horse in Presidio County, Texas, has become the first equine case of New World screwworm in the current U.S. outbreak. Texas issued a new infested zone order on Sept. 9.
Which areas are now restricted? The Sept. 9 order created an infested zone in parts of Presidio and Jeff Davis counties. Warm-blooded animals cannot leave it without authorization, inspection, and any required treatment.
How many U.S. cases have been confirmed? Forty-nine as of Sept. 9, including 48 in Texas, with four still active, according to USDA data compiled by Texas Public Radio.
What should horse owners check? Inspect horses daily for wounds, swelling, drainage, foul odor, or maggots, with extra attention to small cuts, surgical sites, foal navels, and moist areas around the face and genitals.
Can people get screwworm? Rarely. The CDC says the risk to the public is very low, and no locally acquired human infestations have been reported in the United States.
Is beef or other meat safe to eat? Yes. USDA says screwworm is not a food safety threat, and inspection systems are designed to keep infested animals out of the food supply.
How do I report a suspected case? In Texas, contact a Texas Animal Health Commission region office or call its veterinarian-on-call line at 1-800-550-8242. Owners elsewhere should contact a veterinarian and their state animal health official.
