Official Site of The State of New Jersey

New World screwworm (NWS), Cochliomyia hominivorax, is a species of fly found throughout portions of North, Central, and South America and the Caribbean. NWS is particularly devastating because the fly larvae burrow and feed on living tissue, often causing severe, sometimes fatal damage to animals. NWS can infest any warm-blooded animal, including livestock, companion animals, wildlife, and birds. 

If you suspect NWS in any of your animals, please notify your veterinarian immediately and contact the NJDA, Division of Animal Health: (609) 674-6400.

What to look for:
• Maggots in wounds or other body openings, such as the nose, ears, genitalia, or navel (in newborn animals);
• Wounds that have a bloody discharge or foul odor;
• Wounds that become deeper and larger as the maggots grow and feed on living tissue;
• Animals that have recently given birth, suffered an injury, or undergone a procedure (such as ear tagging, dehorning or branding), making them more vulnerable to attracting NWS;
• An animal newly arrived from a region or state with an infestation zone with any of the above signs.

Background
In 1966, the NWS was eradicated in the United States with a sterile insect program developed by the United States Department of Agriculture (USDA). This sterile insect program created a barrier zone in Panama, keeping most of North and Central America free from NWS and preventing expansion into the United States. A breakthrough incursion in Central America occurred in 2023 and NWS progressed steadily northward, and since last year, reported cases nearing the U.S.-Mexico border has pressed the USDA to take proactive steps to prepare against NWS in the United States.

The USDA stopped moving cattle, horses, and bison across the U.S.-Mexico border. Mexico’s National Service of Agro-Alimentary Health, Safety, and Quality (SENASICA) continues to report additional NWS cases in domestic animals. Reported cases are updated regularly on the USDA website map and on their data dashboard. By spring 2026, cases were emerging within dozens of miles from the Texas-Mexico border, and in early June 2026, the first cases of NWS in Texas and New Mexico were confirmed. Primarily affected species included bovine, equine, canine, and swine. Affected areas and surrounding zones are treated with the release of sterile flies.

A U.S.-based sterile fly dispersal facility in Edinburg, Texas has been established, with a new production facility breaking ground in April 2026. This facility expands USDA’s ability to disperse sterile flies along the southern border and into affected areas in the United States. The Food and Drug Administration (FDA) has also provided emergency use authorizations for treatments that can be used to prevent and treat NWS infestations on a broad range of animals, with continuous review and announcements being made frequently.