New World Screwworm Cases Surge Along Southern Border

The number of active new screwworm cases in the United States jumped to 65 this week—more than triple the 21 active cases of the flesh-eating parasite reported on Oct. 19, the U.S. Department of Agriculture (USDA) announced on Nov. 11.

In New Mexico, state officials reported 40 confirmed cases as of Nov. 11, a sharp increase over the four active cases the state reported two weeks ago.

Arizona had six confirmed cases spread across three counties, up from one active case on Oct. 29. The state confirmed its first case on Oct. 28 in Cochise County.

Meriwether Farms, a Wyoming beef company, questioned if the rise in cases was the result of recently imported cattle.

“New World Screwworm [is] now in Arizona,” the farm company posted on X. “But we were told that opening the border to cattle imports from Mexico would be safe and everything was under control?”

Texas reported 23 active cases as of Nov. 10, up from seven on Oct. 29. In all, the state has confirmed 79 cases since June 3.

Its latest detection, an infected sheep in Val Verde County, prompted officials to designate portions of Terrell and Val Verde counties as updated infested zones.

The state’s Parks and Wildlife Department staff continues to investigate animals and monitor game cameras at state parks, management areas, and locations with infested zones.

In Texas, confirmed cases have been found in 23 counties, mostly along the southern border, since June 3, the USDA reported.

There have been 128 total confirmed animal cases in the United States this year. Two of those were found in wildlife, according to the USDA.

The latest case was confirmed on Nov. 11 in Otero County, New Mexico.

Six wild screwworm flies were also trapped, the agency reported.

The USDA did not return several requests for information about the increase in screwworm cases following the reopening of the southern border to Mexican cattle imports.

The southern livestock ports, which closed in May 2025, started to reopen to livestock in August after the number of screwworm infections began to drop.

The Douglas, Arizona, port opened for cattle trade on Aug. 24, followed by Santa Teresa, New Mexico, which opened on Sept. 24 for Mexican cattle and on Oct. 26 for horse imports. The port at Columbus, New Mexico, partially reopened for cattle imports on Oct. 26.

The next port scheduled to reopen is Nogales, Arizona, on Nov. 30.

Mexico had 1,545 active cases through Nov. 9, the USDA stated.

The New World Screwworm Rapid Response team, a coalition of federal and international partners led by the USDA to contain and eradicate the parasitic flies, has released more than 1 billion sterile flies to disrupt the pests and eradicate the infestations since they began to appear in June.

The response team has tested 1,114 suspected samples, mostly from Texas, they reported on Nov. 10.

Texas Parks and Wildlife asked hunters to check their harvested deer this year for signs of the infestation and to report any detections immediately.

“While all warm-blooded mammals can be infested with [New World screwworm], white-tailed deer, jackrabbits, cottontails, small mammals and turkeys are more commonly affected,” the agency stated on its website.