USDA confirms first U.S. case of New World Screwworm in Texas

Federal agricultural officials on Wednesday confirmed the first U.S. case of the destructive New World Screwworm in a Texas calf, triggering emergency quarantine measures.  The U.S. Department of Agriculture’s Animal and Plant Health Inspection Service said the flesh-eating parasite was detected in the umbilical area of a 3-week old calf in Zavala County, Texas, located southwest of San Antonio.

The New World Screwworm is considered one of the most devastating livestock and wildlife pests in history.  Unlike common fly larvae, Screwworm maggots burrow into and feed exclusively on the living flesh of warm-blooded animals, causing severe injury, massive economic loss, and death if left untreated.  While rare, they can also affect humans.

The USDA and the Texas Animal Health Commission have formed a unified Incident Command Team and established a 20-kilometer (12 mile) infested zone around the Zavala County site, implementing strict quarantines and movement controls on live animals.

To eradicate the population, federal officials are expediting the release of millions of laboratory-raised sterile flies, deploying ground release chambers to supplement the 4 million sterile flies already being dispersed aerially in the region each week.  When wild flies mate with the sterile flies, no offspring are produced, eventually collapsing the population.

Because surveillance must continue in areas where sterile flies are released, sterile NWS flies may be caught in traps or reported by the public.  To help officials distinguish sterile flies from wild flies, USDA dyes the sterile pupae.  The dye transfers to the adult flies when they emerge.  The florescent dye glows under UV light and may also be visible to the naked eye.

The USDA noted that its National Veterinary Stockpile is being mobilized to provide treatments and equipment, and that officials are already negotiating with international trading partners to restrict any potential live-animal export bans to specific geographic zones rather than the entire country.

Officials emphasized that the U.S. food supply remains safe, as screwworms do not affect meat processing, and rigorous federal inspections ensure no contaminated product can enter commerce.  Contact your veterinarian immediately if you see any suspicious wounds, maggots, or infestations in your animals or herd.  Animal health professionals should report suspected cases to the State animal health official and APHIS Area Veterinarian in Charge.

Signs of maggot infestations in live or very recently dead wild animals, especially in areas near the U.S./Mexico border, should be reported to your local USDA Wildlife Services office, or call 866-4USDA-WS (866-487-3297).  Contact your healthcare provider if you think you may have Screwworm.  Healthcare providers report suspected cases to the local or State health department.