One month into the New World screwworm outbreak in Texas and the first parasitic fly detection in the United States after it was eradicated in 1966, cases continue to grow.
Two new confirmed cases were reported by the U.S. Department of Agriculture on Tuesday, June 30, bringing the total case count in the U.S. to 29 — a month after Zavala County, Texas, reported the first case in the nation in decades.
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Texas is currently the only state reporting cases, with one of the new cases reported in Pecos County being the first confirmed dog case in Texas.
Uvalde County also reported its first case, bringing the total number of Texas cases to 28, with 22 active and 6 inactive.
Here’s a look at where Texas cases stand as state and federal officials have quarantined 21 counties to prevent the spread of the screwworm.
Livestock roam a field adjacent to Texas State Highway 55 after the confirmed number of U.S. cases of New World screwworm, a parasitic fly that eats warm-blooded animals alive, rose to 15 after three more animals tested positive in two Texas counties, northwest of Rocksprings, Texas, U.S. June 22, 2026.
What is a screwworm
According to the USDA, the New World screwworm is a parasitic fly that impacts livestock, pets, wildlife, and, less commonly, people and birds. The fly’s larvae feed on the living tissue of warm-blooded animals.
Screwworm infestations begin when a female fly lays eggs on a wound or body opening. The eggs hatch into larvae that burrow into the wound and feed on living tissue; then, after about seven days of feeding, the larvae drop to the ground, burrow into the soil and pupate.
What a screwworm looks like
Adult New World screwworms have orange eyes, a metallic blue or green body and three dark stripes across the back, according to the USDA.
The telltale signs of a screwworm infection are the growing wounds or lesions and the presence of feeding maggots on still-alive animals
The New World screwworm is a species of parasitic fly that is well known for the way in which its larvae (maggots) eat the living tissue.
Texas screwworm cases
Here is the breakdown of screwworm case locations in Texas, according to the USDA’s screwworm dashboard, and whether they are considered active or inactive.
USDA classifies cases as inactive when the animal has fully recovered or, in cases where treatment was not performed, when appropriate measures have been taken to prevent the spread of the screwworm, such as the proper disposal of the dead, infested animal.
There are currently 28 cases — 22 active and six inactive — in Texas as of the date they were confirmed:
June 30: One inactive domestic dog case in Pecos County.
June 29: One active domestic cattle case in Uvalde County.
June 27: One active domestic cattle case in Crockett County.
June 26: One active domestic cattle case in Jim Hogg County.
June 24:
One active domestic cattle case in Medina County.
One active domestic sheep case in Edwards County.
Four active domestic sheep cases in Crockett County.
June 23: Three active domestic cattle cases in Terrell County.
June 22: One active domestic goat case in Terrell County.
June 21: Two active domestic cattle cases in Edwards County.
June 20: One active domestic sheep case in Crockett County.
June 12: One inactive domestic sheep case in Sutton County.
June 11:
Two active domestic goat and cattle cases in Edwards County.
One active domestic cattle case in Tom Green County.
One inactive domestic cattle case in Zavala County.
June 9: One active domestic cattle case in Edwards County.
June 8:
One inactive domestic goat case in Gillespie County.
One active domestic cattle case in La Salle County.
June 7: One inactive domestic cattle case in La Salle County.
June 5: One active domestic cattle case in Zavala County.
June 3: One inactive domestic cattle case in Zavala County.
The 29th case in the U.S. was confirmed in New Mexico earlier in the month, but it has now been classified as inactive by the USDA.
Texas Animal Health Commission quarantine zones
A screenshot of the Texas Animal Health Commission New World screwworm quarantine zone map on July 1, 2026.
The Texas Animal Health Commission has placed parts of 21 counties across West, South and Central Texas under quarantine, restricting animal movement to stop the spread of recently reported cases.
Here’s a look at which counties are under quarantine and when the quarantine became effective.
Zone 1 (effective June 3) — Uvalde and Zavala counties.
Zone 2 (effective June 7) — La Salle and Webb counties.
Zone 3 (effective June 9) — Gillespie, Kerr and Kimble counties.
Zone 4 (effective June 10) — Edwards, Sutton and Val Verde counties.
Zone 5 (effective June 12) — Tom Green and Coke counties.
Zone 6 (effective June 13) — Kimble, Schleicher and Sutton counties.
Zone 7 (effective June 20) — Crockett, Schleicher, Val Verde, Terrell and Sutton counties.
Zone 8 (effective June 22) — Terrell and Pecos counties.
Zone 9 (effective June 24) — Bandera, Medina and Uvalde counties.
Zone 10 (effective June 26) — Jim Hogg, Starr and Zapata counties.
Zone 11 (effective June 30) — Uvalde County.
According to the orders placing the counties under quarantine, the quarantine will remain in effect until the commission lifts it.
Texas screwworm map
Mateo Rosiles is the Texas Connect reporter for USA TODAY and its regional papers in Texas. Got a news tip for him? Email him at mrosiles@usatodayco.com.
This article originally appeared on USA TODAY: One month in, Texas screwworm cases climb to 28 as US reaches 29