Texas officials are expanding emergency measures after a second case of New World screwworm was confirmed in South Texas, raising concern among ranchers and state agricultural leaders about the possible return of a parasite that had been eradicated from the United States for decades.
The U.S. Department of Agriculture confirmed the second case in Zavala County, only days after the first Texas detection was reported in a nearby calf. According to reports, the second infected animal was a one-month-old calf found about 5.6 miles from the first confirmed case near La Pryor.
Gov. Greg Abbott issued a disaster declaration for Zavala and Uvalde counties and directed state resources toward the response. The declaration is intended to help state agencies coordinate with federal officials, livestock producers, veterinarians and wildlife authorities as they work to contain the parasite before it spreads further.
New World screwworm is a parasitic fly whose larvae feed on the living tissue of warm-blooded animals. The parasite can infest wounds or body openings and can cause severe injury or death if not treated quickly. It can affect cattle, pets, wildlife and, in rare cases, humans.
TRENDING TODAY
The latest detection has heightened concern because Texas is the nation’s largest cattle-producing state. A wider outbreak could create major problems for ranchers, disrupt livestock movement and increase costs for monitoring, treatment and containment.
State and federal officials have emphasized that the issue is an animal-health and agricultural threat, not a confirmed food safety problem. The USDA has said containment, surveillance and sterile fly release operations are underway.
The sterile fly program is central to the response. Under that method, sterile male flies are released into affected areas. Because female screwworm flies mate only once, mating with sterile males prevents the production of viable offspring and helps collapse the population over time.
The United States used that same strategy to eliminate New World screwworm from the country in the 1960s. Officials are now trying to prevent the parasite from becoming reestablished after it moved northward through Central America and Mexico in recent years.
Texas agencies are also urging ranchers, hunters, veterinarians and animal owners to watch for suspicious wounds, larvae or signs of infection. Early detection is considered critical because infected animals can be treated, but untreated infestations can worsen quickly.
Authorities have increased surveillance and movement controls in the affected region. Livestock and animal movements may face additional restrictions as officials try to prevent the parasite from spreading beyond the current area.
The outbreak remains limited, with only two confirmed Texas cases reported so far. However, officials say the response must be aggressive because the parasite can spread rapidly if not contained.
For Texas ranchers, the concern is not only animal health but also economics. Before eradication, screwworm outbreaks caused major losses across the southern United States. Animals could suffer weight loss, infection, tissue damage and death, creating heavy costs for producers.
Wildlife officials are also watching closely. New World screwworm can infest wild animals, including deer and other mammals, which can make tracking and containment more difficult.
Abbott said state agencies will continue working with federal partners and local officials to protect livestock, wildlife and the agricultural economy.
The next several weeks will be important. If no additional cases are found, officials may be able to keep the outbreak isolated. If more infected animals are identified, Texas could face a broader and more expensive containment effort.
For now, the state is treating the second case as a serious warning sign — not a statewide livestock crisis, but a threat that requires immediate action.
Why It Matters
Texas has the largest cattle industry in the United States, so even a small screwworm outbreak can create major concern for ranchers, veterinarians and state officials.
The parasite does not represent a confirmed food safety issue, but it can seriously harm livestock, pets and wildlife if not detected and treated quickly.
What Comes Next
Texas and federal officials will continue surveillance, animal inspections, movement restrictions and sterile fly releases in the affected area.
Ranchers and pet owners are being urged to check animals carefully and report any suspicious wounds or larvae as officials work to determine whether the two cases are isolated or part of a larger outbreak.
New: Gov. Greg Abbott on Friday expanded a statewide disaster declaration in response to the New World screwworm’s arrival in Texas.
The expanded declaration authorizes the use of “all available resources of state government to respond to this disaster,” Abbott said.…
— Texas Tribune (@TexasTribune) June 5, 2026
