Full Breakdown
New World Screwworm Fly Returns to the United States: Risks for Pets and the Fight to Eradicate It
7/10/2026, 5:11:37 PM
Re-emergence and How the Parasite Infects Animals
In June 2026 a flesh-eating New World screwworm fly was detected in a calf in Zavala County, Texas, marking the first U.S. case in more than 50 years. Female flies deposit eggs in open wounds or mucous membranes; the eggs hatch within hours and the larvae feed on living tissue for about a week before dropping to the ground to mature into adult flies. The larvae can infest any warm-blooded mammal, including cattle, dogs, cats, wildlife, and, rarely, humans.
Geographic Spread and Confirmed Cases
The fly migrated north from Panama in 2024, moved through Mexico in 2025, and reached the U.S. border in late May 2026. As of July 7 2026, the USDA’s online dashboard lists active detections in six Texas counties—Terrell, Crockett, Edwards, Uvalde, Medina, and Jim Hogg—and one inactive county in eastern New Mexico. Sources report more than 30 confirmed instances in Texas and New Mexico, including two dog cases (one in each state).
Economic and Public-Health Stakes
Agriculture officials warn the pest threatens the $113 billion U.S. cattle industry; beef prices have risen to a record $6.75 per pound. While the USDA states the screwworm does not affect food safety, extensive livestock loss could depress meat production. Human infection remains very low, with a single CDC-confirmed case in August 2025 linked to travel in El Salvador.
Federal and State Response
The U.S. Department of Agriculture (USDA) has revived the sterile-male release program that eliminated the fly in the 1960s. It invested $21 million to convert a southern-Mexico facility from fruit-fly to screwworm production and plans a $750 million fly-factory in Texas slated to open next year. State agencies—including the Texas Animal Health Commission (TAHC) and Texas A&M AgriLife Extension—have issued surveillance maps, quarantine orders for more than 20 counties, and a 1-800 hotline (1-800-550-8242).
Guidance for Pet Owners
Veterinarians advise daily inspection of pets for open wounds, maggots, foul odor, restlessness, or “hyper-fixating” on a body area. Prescription flea- and tick-preventive medications are recommended because they kill larvae when ingested. If infestation is suspected, owners should seek immediate veterinary care for larval removal, wound cleaning, and possible antibiotics.
Criticism and Inter-State Restrictions
In mid-June, Florida blocked the acceptance of rescue dogs and cats from Texas and New Mexico, citing the screwworm risk. Animal-welfare groups have expressed concern that travel bans could impede rescue operations, though officials argue the measures protect local animal populations.
Conflicting Data on Case Numbers
One source cites “more than 30 confirmed instances” across Texas and New Mexico, while another reports “5 confirmed in Texas, largely in cattle, plus 1 dog case in New Mexico.” Both figures appear in official updates, indicating a lack of a single consolidated count.
Verbatim Quotes
- “It will kill the larvae as they ingest the blood and tissue,” — Melissa Stansell, Veterinarian, Austin Pets Alive!
- “The chemical compositions of those products are what kill the actual larval stages of these flies.” — Melissa Stansell, Veterinarian, Austin Pets Alive!
- “It is only fatal if left untreated,” — Melissa Stansell, Veterinarian, Austin Pets Alive!
Upcoming Actions
The USDA continues to update its online screwworm dashboard, and the Texas factory for sterile flies is expected to become operational in 2027. Pet owners are urged to maintain vigilance, use preventive medications, and contact TAHC or a veterinarian at the first sign of infestation.
