Two Traps Caught Fertile Screwworm Flies, and Texas Redrew the Map in a Day

Every screwworm story Texas has run since June has started the same way: an animal with a wound, a sample, a confirmation, a quarantine line drawn around a pasture. Friday's story starts in a trap.

The Texas Animal Health Commission posted three executive director orders on Oct. 31, all signed the same day by Dr. Lewis R. Dinges and effective immediately. Two of them say the same unusual sentence about two different counties. On Oct. 30, a trapped fertile wild New World screwworm fly was identified by the U.S. Department of Agriculture — one in Pecos County, one in Hudspeth County. Neither came out of a living animal. Both came out of the surveillance network.

What followed was a rewrite of the map in a single afternoon. Infested Zone 23, which covers parts of Brewster, Jeff Davis, Pecos and Reeves counties and was created on Oct. 21 after a bovine detection in Jeff Davis County, became Zone 23.A. Infested Zone 25.A, the El Paso and Hudspeth footprint created on Oct. 28 after a dog in Socorro tested positive, became Zone 25.B. And a brand new designation appeared: Infested Zone 27, covering parts of Culberson and Hudspeth counties, triggered by a screwworm detection in a Hudspeth County bovine on Oct. 30.

The word in the order

"Fertile wild" is doing real work in those documents. The response in Texas runs on sterile insects — irradiated males released by air and from ground chambers to swamp the wild population with mates that produce nothing. A surveillance trap catches both kinds, and a sterile released fly is not evidence of anything except that the program is flying. A fertile wild fly is the other category entirely: an insect that was not sterilized in a facility, caught outdoors, in a county with an active zone.

The orders do not say where that fly came from, whether it mated locally, or how old it was. What they establish is narrower and still consequential. The trap network is the same instrument the commission uses to decide when a zone can be released — the release criteria in prior orders name fly trapping and monitoring data, sterile fly dispersal evaluation, and no detections inside the area. The tool that certifies the end of an outbreak has now produced detections in two counties on the same day, and both zones were rewritten within twenty-four hours.

For anyone moving animals, the practical content of all three orders is identical to what came before. No warm-blooded animal inside a zone leaves without prior authorization from the commission. Leaving requires inspection and treatment as the commission specifies, plus a permit or certificate issued by a commission representative. Hides, carcasses and parts of any animal capable of hosting screwworm must be inspected and treated before they come out. Unauthorized movement carries administrative penalties and possible criminal prosecution.

The legal footing under all of it is a pair of gubernatorial proclamations. Gov. Greg Abbott issued a statewide disaster proclamation for all Texas counties on Jan. 29, 2026, on the threat alone, before the parasite arrived, and renewed it monthly. A second statewide proclamation followed the June 5 detection, renewed July 4, Aug. 3, Sept. 2 and Oct. 2.

Culberson is the new name

Sixteen counties now appear on the commission's notice page, and Culberson is the one that was not there before this week. It is a hard county to picture for most Texans: county seat Van Horn, Interstate 10 running through it between Hudspeth and Reeves, the Guadalupe Mountains and the state's highest peak on its western side, and the New Mexico line across its northern edge. The zone does not cover the county — the order designates "the following areas," with the boundary drawn on the map attached to the order — but a county that had no screwworm footprint on Thursday had one on Saturday.

The county count has moved all week. A KBTX report on Oct. 31 put the restricted area at 14 counties; the commission's own notice, checked Nov. 1, lists 16, from Brewster and Crockett in the east to Culberson and El Paso in the far west.

Nationally the case ledger is still small and still growing. As of Friday, Texas had confirmed 58 cases since June 3 with eight listed as active, the most recent a Presidio County bovine confirmed Oct. 28, according to figures the Silver City Daily Press pulled from state and federal agriculture officials. New Mexico had 14 confirmed and 12 active — seven cows, two horses, three dogs, one cat and one sheep, spread across Grant, Luna, Doña Ana, Hidalgo and Otero counties. Arizona's first case, a dog in Cochise County, was confirmed Oct. 28. The only wildlife detection in the country remains the hunter-harvested elk in Pecos County on Oct. 21, now inactive.

That cat is worth a sentence. It came from a residence between Silver City and Mimbres, had been attacked by another animal, and was taken to a veterinarian for the wound. The larvae turned up when the vet cleaned it. It is Grant County's fourth case and the first feline in the U.S. outbreak — and it is the ordinary mechanism, not an exotic one. Screwworm needs broken skin. A cat that fights outdoors has broken skin, and a cat is far harder to inspect daily than a calf in a pen.

Which is the uncomfortable symmetry in this week's news. The counties that got new zones got them because traps worked, and the animals that keep turning up positive are pets and livestock living where the fly already is. Sixteen counties, three rewritten orders, and the number that matters next is not how many more animals test positive. It is whether the next trap comes back with something sterile in it.