On June 3, 2026, the USDA's Animal and Plant Health Inspection Service (APHIS) confirmed the detection of New World screwworm (NWS) in a three-week-old calf in Zavala County, Texas — the first confirmed domestic animal case in nearly 60 years, since the pest was eradicated from the United States in 1966. The calf, found approximately 50 miles from the Mexican border at a ranch in La Pryor, had larvae identified in its umbilical area. The animal was treated and survived.
By June 8, 2026, USDA had confirmed five additional cases: a second calf in Zavala County, a calf in La Salle County, approximately 80 miles southeast of the original detection, a goat in Gillespie County, about 170 miles north, and an infested dog whose tissue samples were submitted by a veterinary clinic in Andrews County, nearly 400 miles north of Zavala County. That dog case was reclassified: USDA APHIS announced the dog actually resided in Lea County, New Mexico, making it the state's first confirmed NWS case.
As of June 11, 2026, USDA data confirmed nine total cases in cattle, goats, and a dog, across Zavala, La Salle, Gillespie, and Edwards counties in Texas, and Lea County, New Mexico. The Texas Animal Health Commission (TAHC) has placed an active quarantine on 13 Texas counties: Coke, Edwards, Gillespie, Kerr, Kimble, La Salle, Schleicher, Sutton, Tom Green, Uvalde, Val Verde, Webb, and Zavala. Warm-blooded animals in quarantine zones cannot leave without prior TAHC authorization and inspection.
Governor Greg Abbott activated the Texas State Emergency Operations Center and issued a statewide disaster proclamation covering all Texas counties. "This is a highly treatable condition if you act on it immediately," Abbott stated. "We have beaten this before and we will do it again."
The Public Health Risk — Including for Pets and People
New World screwworm is a parasitic fly — Cochliomyia hominivorax — whose larvae burrow into the living tissue of warm-blooded animals and feed on healthy flesh rather than dead tissue, which distinguishes it from most other fly species. The burrowing behavior enlarges wounds rapidly, creates bacterial infection risk, and can kill an untreated animal within one to two weeks.
USDA APHIS has confirmed that NWS can infest livestock, pets, wildlife, and, in rare cases, people. The New Mexico dog case is particularly significant because companion animals travel across state lines and move in proximity to families in ways that quarantined livestock cannot. "Though rare in people, anyone who notices a suspicious lesion should seek immediate medical care," USDA stated in its June 8 press release.
Outdoor workers, hunters, hikers, and anyone with open wounds who have spent time in affected areas of south and southwest Texas should remain alert to any wound that appears to enlarge, contains moving material, or fails to heal normally. The CDC has confirmed that no locally acquired human infestations have been reported in the United States during the current outbreak, but risk exists in areas where NWS flies are circulating.
On June 11, 2026, the FDA issued an Emergency Use Authorization for generic Nitenpyram Tablets to treat NWS infestation in dogs, cats, puppies, and kittens weighing at least two pounds and at least four weeks old. Available over the counter in two tablet sizes, the drug works by killing most NWS larvae within hours of the first dose, the first generic animal drug ever authorized for use against screwworm.
| Case Location | Animal Affected | Approx. Date Confirmed |
| Zavala County, TX (La Pryor) | Calf | June 3, 2026 |
| Zavala County, TX | Calf | June 5, 2026 |
| La Salle County, TX | Calf | June 8, 2026 |
| Gillespie County, TX | Goat | June 8, 2026 |
| Lea County, NM | Dog | June 8, 2026 |
| Edwards County, TX | Additional case(s) | By June 9, 2026 |
| Total as of June 11 | 9 confirmed | Cattle, goats, dog |
The Response Effort — and Why It Will Take Time
The proven tool for NWS eradication is the sterile insect technique — mass release of sterile male flies that mate with wild females but produce no viable offspring, gradually collapsing the wild population. USDA began releasing sterile flies on June 4, initially deploying 2 million sterile flies twice weekly by air and 4 million per week via 24 ground release chambers in and around the detection zone. Treatment supplies from the National Veterinary Stockpile have been relocated to Texas and made available through the TAHC.
However, leading veterinary parasitologist Christopher Lee, DVM, MPH, DACVPM, cautioned that the first Texas detection "almost certainly understates the threat," and that fully scaling sterile-fly production could take 18 months to two years. Lee stated, "This is the first time that we've documented it, but the likelihood is that we have potentially hundreds to thousands of these flies now here."
The USDA confirmed that the U.S. food supply is not at risk. NWS does not infest meat, fruits, vegetables, or other food products, and any affected animal would be identified during mandatory FSIS inspection before entering commerce. The federal tracking website Screwworm.gov and a 24-hour response hotline are now operational, with USDA case maps updated multiple times per week.
Texas pet owners and livestock producers should inspect all animals daily for unexplained wounds or the presence of larvae, treat open wounds immediately with veterinarian-recommended products, and report any suspected infestation to the TAHC at 1-800-550-8242 or via their nearest regional office. Human exposure concerns should be directed to the Texas Department of State Health Services or a physician, with prompt disclosure of any travel to affected areas.
Frequently Asked Questions
What is New World screwworm, and why is it back in the United States?
New World screwworm is a parasitic fly (Cochliomyia hominivorax) whose larvae burrow into and feed on living flesh, causing severe and potentially fatal wounds in warm-blooded animals. USDA eradicated it from the U.S. in 1966 using sterile insect releases. The current outbreak originated in Mexico and Central America and spread northward through Mexico until crossing into South Texas in June 2026.
Is the U.S. food supply at risk?
No. USDA has confirmed that NWS does not infest meat, fruits, vegetables, or any food products. USDA FSIS inspection processes ensure that any affected animal is identified before entering commerce.
Can screwworm infest pets or people?
Yes, though human infestation is rare. The CDC confirms no locally acquired human infestations have occurred during this outbreak, but the risk exists for people with open wounds in areas where NWS flies are active. The New Mexico dog case confirms that companion animals are a genuine risk category.
What should Texas and New Mexico pet owners do?
Inspect pets daily for any wounds, enlarging lesions, or signs of larvae. The FDA has authorized a generic nitenpyram tablet available over the counter for treating NWS in dogs and cats. Contact a veterinarian immediately if you see any suspicious wounds, and stay current with updates at Screwworm.gov.
How is the government trying to stop the outbreak?
USDA is deploying millions of sterile NWS flies weekly via air and ground release to suppress the wild fly population. A quarantine restricts warm-blooded animal movement across 13 Texas counties. Governor Abbott activated the State Emergency Operations Center. A $750 million sterile fly production facility is being constructed in Texas. For the latest confirmed case map and updates, visit TAHC or Screwworm.gov.
