The U.S. Department of Agriculture has confirmed New World screwworm in a horse in Grant County, New Mexico’s second confirmed case since the parasite returned to the state in June. The detection comes days before federal officials planned to resume livestock imports through the Santa Teresa port on September 24, creating an immediate test for the state’s animal-health safeguards.
The new infestation was confirmed Thursday, according to Reuters’ report citing USDA records. State agriculture officials said the source of the horse’s infestation was still under investigation and did not immediately say whether the finding would change the port schedule. That distinction matters: the confirmed animal-health event is separate from any decision about cross-border trade, which remained unresolved when the case was reported.
New World screwworm is a parasitic fly whose larvae enter open wounds and feed on living tissue. New Mexico’s multi-agency information center says untreated infestations can kill an animal within seven to 10 days. Warning signs include wounds that worsen instead of healing, visible larvae, swelling, discharge, foul odor and unusual behavior. Livestock owners, veterinarians and pet owners are urged to report suspected cases immediately rather than move an affected animal.
The latest case follows the state’s first confirmed detection on June 7 in a dog in Lea County. New Mexico officials then established a roughly 12-mile infested zone, increased trapping and surveillance, and required animals in the zone to be inspected and treated when necessary before movement. The Department of Agriculture’s response notice said routine travel generally continued unless inspectors identified a heightened risk tied to an animal’s condition or wounds.
State guidance explains that a confirmed livestock case can lead to another regulatory zone, but the boundaries and movement rules depend on the location, epidemiological findings and nearby animal populations. Within such a zone, officials may conduct tracing, fly trapping, treatment and movement inspections under the state’s infested-zone protocol. No new Grant County zone had been publicly detailed at the time of the federal confirmation.
USDA describes the current risk to people and animals nationally as very low and says the food supply remains safe. Its federal response page outlines border surveillance, animal-movement controls and expanded production of sterile flies, which are released to mate with wild flies and interrupt reproduction. The agency says planned capacity will approach 500 million sterile flies a week.
For New Mexico producers, the practical response is immediate wound monitoring and prompt reporting. Suspected livestock, wildlife or pet cases may be reported to the New Mexico Livestock Board at 505-841-6161; the after-hours AgroGuard hotline is 1-800-525-2782. Until officials publish the Grant County response boundaries and a decision on Santa Teresa, animal owners should treat both the geographic controls and the trade timetable as pending rather than assume either is unchanged.
