El Paso, Texas: Screwworm Found in a Socorro Dog and Hudspeth Cattle Sets Quarantine Zones for the Borderland

New World screwworm has reached the Borderland. The El Paso Times reported this week that the flesh eating parasite was detected in a dog in El Paso County and in livestock in Hudspeth County and near Las Cruces, New Mexico, the first reported cases in the region.

State officials have answered with quarantine zones on both sides of the state line. Much of eastern and southern El Paso County and most of Hudspeth County now sit inside a Texas Animal Health Commission infested zone, and ranch country around Las Cruces and Santa Teresa in New Mexico is under its own infested zone designations.

The first Borderland cases

In El Paso County, screwworm was detected on October 27 in a dog in Socorro, found through a veterinarian. A commission spokesperson told the El Paso Times by email that the dog spent time outdoors but was not around cattle.

In Hudspeth County, screwworm was found on October 23 in two cows at separate rural locations where other livestock are kept, the commission spokesperson said. In Dona Ana County, New Mexico, it was detected on October 25 in a sheep on the New Mexico State University campus in Las Cruces and in a cow at an off campus location, according to New Mexico Department of Agriculture officials reported by the El Paso Times.

State Representative Mary Gonzalez warned in a statement that the pest affects animals beyond livestock and urged owners to check their pets and watch them closely.

Quarantine zones and movement rules

The Texas Animal Health Commission designated much of eastern and southern El Paso County and most of Hudspeth County as Infested Zone 25.A. The El Paso Times reported that the zone restricts the movement of livestock, but not pets. The commission's own orders moved in steps late this week: a modified order covering El Paso and Hudspeth counties on October 28 and an El Paso County order on October 29.

The commission's emergency page says there are movement restrictions in the infested zones and that warm blooded animals inside a zone may not move out of it without prior authorization from the commission. Owners planning a move must contact the commission or a certified screwworm inspector to set up an inspection, and a certified inspector completes a movement and treatment certificate listing the product used and the animals' official identification. The Las Cruces and Santa Teresa areas in New Mexico carry infested zone designations that also restrict livestock movement, not pets, the El Paso Times reported.

A pest that was gone for sixty years

Screwworm was eradicated from the United States in 1966 with the sterile insect technique, in which sterile flies are released to break the breeding cycle. The parasite reappeared in Central America in 2023 and spread through Mexico, and the first animal case in the United States in this wave was reported in June 2026. The Texas commission says a calf in Zavala County was confirmed on June 3, 2026, and has since recovered, and that sterile fly dispersal work, from the ground and the air, is underway in the affected areas.

The timing matters for the Borderland cattle trade. The United States Department of Agriculture reopened cattle crossing ports on the border this summer and fall after they had been closed for more than a year because of the spread of screwworm in Mexico. The Santa Teresa port, the largest cattle border crossing in North America, reopened on September 24. The Columbus, New Mexico port reopened on October 26, and the Douglas, Arizona port reopened on August 24.