First Rio Grande Valley screwworm case confirmed in Starr County

New World screwworm has reached the Rio Grande Valley, prompting state and federal officials to establish an infested zone after the parasite was confirmed in a domestic cow in Starr County.

The pest, a parasitic fly whose larvae feed on the living tissue of warm-blooded animals, was eradicated from the U.S. decades ago, but reemerged in Texas earlier this year, prompting an ongoing response by state and federal animal health officials.

As of Sunday, the U.S. had recorded 41 confirmed cases, including the one in Starr County. Twelve of those remain active, while 29 have been declared inactive.

The Texas Animal Health Commission announced Saturday that the infested zone encompasses Starr County and extends into portions of neighboring Zapata County. The designation is meant to contain the parasite and reduce the risk of it spreading to additional livestock.

The new zone triggers movement controls for livestock and other warm-blooded animals. Animals leaving the zone must meet inspection and permitting requirements before they can be transported to help prevent the parasite from spreading into unaffected areas.

The Texas Animal Health Commission and USDA said the Starr County infested zone will remain in effect until officials determine conditions have been met to lift the restrictions.