Screwworm Count Reaches 49 as First Horse Case Lands in Presidio County

The New World screwworm outbreak has added its 49th U.S. case — and its first horse. USDA's case-level dashboard confirmed an infestation in a horse in Presidio County on September 9, making the Big Bend county the 17th in Texas with a confirmed case.

Track every confirmed case on our live Texas screwworm tracker and county map.

Forty-eight of the 49 U.S. cases are in Texas; the remaining case is the dog confirmed in Lea County, New Mexico, in early June. Only two cases are now listed as active under mitigation, with 47 inactive — matching the lowest active count since mid-August.

First equine case, in a county already under quarantine

Until now the outbreak had hit cattle, sheep, goats and dogs. The Presidio County horse is the first confirmed equine case, a reminder that any warm-blooded animal with an open wound is at risk. Presidio County had been inside the TAHC infested zone since July 30 without a confirmed case of its own.

The same day the case was confirmed, the Texas Animal Health Commission issued an Executive Director Order designating new infested areas in Presidio County and neighboring Jeff Davis County — the first new county added to the quarantine map since early August. Warm-blooded animals may not leave an infested zone without prior authorization, inspection, any required treatment and a movement certificate.

September shrinks the quarantine map from 19 counties to 14

Even as the new case landed, TAHC spent September lifting restrictions faster than it adds them. Release orders on September 3 cleared Coke and Tom Green counties plus designated areas of Uvalde and Zavala — the county where the outbreak's index case was confirmed in June. A modified order on September 4 released parts of Kimble, Schleicher and Sutton, taking Kimble off the map entirely, and a September 16 order released Bandera, Medina and designated areas of Uvalde.

Movement restrictions now cover parts of 14 counties: Brewster, Crockett, Edwards, Jeff Davis, Jim Hogg, Pecos, Presidio, Schleicher, Starr, Sutton, Terrell, Uvalde, Val Verde and Zapata — down from 19 at the start of the month.

The September 9 confirmation is the first new U.S. case since the August 31 dog case in Crockett County. USDA says it has released more than 1 billion sterile flies in Texas since February and is aiming to raise production to 500 million flies a week by next summer.