USDA Confirms New World Screwworm Detected in Texas Calf, Triggering Federal Response
A confirmed screwworm detection on U.S. soil — the first in Texas in decades — activates federal agricultural containment protocols and raises questions about the status of the U.S.-Mexico border...
The U.S. Department of Agriculture confirmed on June 3, 2026, that New World screwworm (Cochliomyia hominivorax) larvae were identified in a three-week-old calf in Zavala County, Texas, according to a USDA statement reported by CBS News. The USDA said the affected animal was a single calf, with larvae found in its umbilical area. The agency did not confirm additional affected animals in the initial disclosure.
New World screwworm is a parasitic fly whose larvae feed on the living tissue of warm-blooded animals. The USDA Animal and Plant Health Inspection Service (APHIS) declared the species eradicated from the United States in 1966 following a decades-long joint federal and state eradication program, according to APHIS historical records. Any confirmed detection on U.S. soil triggers mandatory APHIS response protocols under 7 U.S.C. § 8301 et seq., the Animal Health Protection Act.
Zavala County is located in southwest Texas, approximately 60 miles from the U.S.-Mexico border. APHIS operates a Sterile Insect Technique (SIT) program in cooperation with Mexico and Panama to suppress screwworm populations, releasing sterile flies along a biological barrier in Panama. APHIS budget documents submitted to Congress for fiscal year 2026 listed the screwworm eradication program at approximately $18.7 million in annual funding, according to USDA Congressional Budget Justification filings.
As of the time of publication, the USDA had not disclosed whether additional livestock in Zavala County or neighboring counties had been inspected or tested, nor had it confirmed the source of the infestation. The agency also had not stated whether the Texas detection was linked to any breakdown in the Panama barrier program.
What remains unknown: whether additional animals in the region are infected, the vector pathway of this specific case, and whether APHIS has issued a formal federal order restricting livestock movement in Zavala County. APHIS Federal Order records, available through the APHIS website, would document any movement restrictions. A USDA APHIS Freedom of Information Act request for the full case report and any internal epidemiological assessment would provide further detail on the scope of the federal response.