The New World screwworm fly is a species of parasitic fly that is well known for the way in which its larvae (maggots) eat the living tissue. (Image Credit: ID 354754062 © Mikowibowo Dreamstime.com)

By Alice McFarlane

New World Screwworm

Deadly pest detected in the United States

Jun 5, 2026 | 10:04 AM

The U.S. Department of Agriculture’s Animal and Plant Health Inspection Service confirmed a New World screwworm (NWS) in a bovine in Texas.

NWS is a serious pest that affects livestock, pets, wildlife and, less commonly, people and birds. Its larvae burrow into the flesh of living animals, causing serious damage to livestock and economic losses.

The affected animal is a three-week-old calf. Larvae were identified in its umbilical area. There have been no further detections to date.

USDA Under Secretary for Marketing and Regulatory Programs Dudley Hoskins said all models showed NWS first entered the country in 2025 but was contained.

“Protecting our livestock industry is a national security issue of the utmost importance, and USDA is wasting no time in taking action,” Hoskins said. “USDA invested heavily in the tools needed to eliminate NWS ever since cases started increasing in Central America and Mexico. The United States has defeated this pest before, and we will do it again.”

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USDA and Texas officials formed a unified incident command team with the Texas Animal Health Commission and are deploying response personnel to the area. A 20-km infested zone has been established around the infected animal. Quarantines, movement controls and surveillance are underway.

Sterile fly release is the primary weapon against screwworm. Another four million sterile flies will be released each week in the area. Trapping for NWS flies will also increase along the border and just outside the dispersal area.

USDA said the U.S. food supply is safe. Screwworms do not infest meat, fruits, vegetables or other food sources.

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alice.mcfarlane@pattisonmedia.com

by Alice McFarlane

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Deadly pest detected in the United States

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