The USDA has confirmed a New World screwworm infestation in a 3-week-old calf in Zavala County, Texas, marking the first domestic case in the current outbreak. 

The USDA and Army Corps of Engineers have begun construction of a sterile fly production facility in Edinburg, Texas. This facility will expand capacity and help protect livestock, wildlife, pets, and people from New World screwworms. 

The USDA has announced that the dispersal facility in Edinburg, TX is complete and ready to begin distributing sterile New World screwworms along the U.S.-Mexico Border. 

The USDA has announced that sterile fly releases will be shifting to Northern Mexico and Southern Texas, to reinforce coverage along the border and create a buffer zone to help prevent the spread of New World screwworms into the U.S. 

The USDA has launched a centralized screwworm website that it will use to organize and disseminate information related to this important pest. This website includes up-to-date distribution maps and information for stakeholders, the general public, veterinarians, and more.

New World screwworms have continue to be detected further north in Mexico. The early July site in northcentral Veracruz (as shown on the map below) has been declared inactive, but cases have continued to spread in Oaxaca and southern Veracruz. The most recent announcement is of a confirmed case in Nuevo Leon, approximately 70 miles south of the US-Mexico border.

New World screwworms have been detected further north in Mexico, resulting in the closure of Ports of Entry for livestock entering the U.S. from Mexico. The map below shows the current detection events of New World screwworms in Central America and Mexico (as of July 9th, 2025), along with the US ports of entry that are suspended to livestock movement.

The OSU Extension Livestock Entomology Program develops and conducts Extension and applied research programs to inform livestock producers of the best management practices of ticks, flies, lice and other parasites of cattle, horses, sheep and goats, poultry, and swine.

Dana Zook, OSU Extension Area Livestock Specialist, and Dr. Barry Whitworth, OSU Extension Area Food and Animal Quality Health Specialist, talk about the biology and historical impact of New World screwworm. 

The New World screwworm is a parasitic pest once common in Oklahoma during warmer months, with seasonal migrations from southern states where it could survive the winter. 

Dr. Rosslyn Biggs, OSU Extension beef cattle specialist, shares important information about the newly approved treatment for New World screwworm, a dangerous parasite that threatens livestock health. 

(Dec. 20, 2025)

Learn what New World screwworm is, why it threatens livestock and wildlife, how infestations occur, and what steps producers can take to identify, report and prevent outbreaks. 

Assistant Professor and State Extension Specialist for Livestock  Entomology and Parasitology

(405)744-9064

jonathan.cammack@okstate.edu

Professor for Entomology & Plant Pathology
(405) 744-9420 
justin.talley@okstate.edu

Assistant Professor for Veterinary Clinical Sciences
(405) 744-8587
rosslyn.biggs@okstate.edu