Texas has established a new infested zone in Terrell County after New World screwworm was confirmed in sheep there, and warm-blooded animals can no longer leave that area without inspection by a certified inspector. The detection is the most recent in an outbreak that USDA now counts at 45 confirmed U.S. detections.
The number that changed most usefully is the smaller one. Only five of those 45 cases remain active, all in Texas, according to USDA Animal and Plant Health Inspection Service data. When MedicalDaily reported the count at 42 cases with 10 active roughly a week ago, twice as many animals were still under treatment. Besides Terrell County, the active cases are in Sutton, Starr, and Brewster counties, the last with two.
For households along the border, the practical consequence is geographic rather than statistical. Terrell County sits on the Mexican border in a stretch of West Texas, and the new zone changes what livestock and pet owners in that area must do before transporting an animal.
The Terrell County Detection and the New Zone
The infestation was reported in sheep. Most confirmed cases in this outbreak have been in cattle, though sheep, goats, and dogs have all been affected since the first detection.
Because of the detection, Texas established a new infested zone in which warm-blooded animals cannot leave the area without inspection by someone certified through the Texas Animal Health Commission. That certification program was developed to handle inspection volume during this response.
Movement restrictions now cover parts of more than 20 Texas counties, stretching from the Rio Grande Valley through West Texas and the Hill Country. Property owners can check whether a specific address falls inside a zone through the Texas Animal Health Commission, which maintains a searchable map of infested areas.
Active Cases Versus Cumulative Detections
The distinction between the two figures is the most important thing in the current data, and headlines that report only the cumulative number obscure it.
APHIS defines an active case as one still requiring mitigation on the individual animal, meaning treatment and wound management until the animal is free of infestation. A case becomes inactive when the animal has fully recovered or when carcass management has prevented further spread. The APHIS detection dashboard also cautions that an infested zone can remain active even after the individual animal case is closed.
The cumulative count of 45 therefore describes everything found since the first confirmed detection, a calf in Zavala County confirmed June 3, while the active count of five describes what is currently being managed.
Geographic concentration has also held. All but one of the confirmed detections have been in Texas, with the single exception in New Mexico. USDA has expanded surveillance across affected areas using drone flights, trail cameras, and fly trapping, and that intensity cuts both ways in interpreting the numbers. More looking produces more finding, which means a rising cumulative count does not by itself indicate accelerating spread.
Livestock Owners and Pet Owners Near the Border
Detection still depends on someone noticing a wound, because technology has not replaced that step. Screwworm larvae feed on living tissue, and a wound as small as a tick bite, a scratch, or a natural body opening can attract a female fly. Newborn animals are particularly vulnerable at the navel.
USDA advises checking pets and livestock for draining or enlarging wounds and signs of discomfort, and looking for larvae or eggs in or around the nose, ears, genitalia, or the navel of newborn animals. Veterinarians recommend inspecting animals after injuries, surgical procedures, branding, or anything else that creates an open wound.
Suspected cases in Texas livestock or companion animals should be reported to a Texas Animal Health Commission region office or the 24-hour veterinarian on-call line at 1-800-550-8242, within 24 hours of a suspect or confirmed case. Owners outside Texas should contact their veterinarian and state animal health official.
Human infestation is uncommon but possible. CDC assesses the risk to people as low and reports no human cases acquired inside the United States in this outbreak. Anyone who notices a suspicious wound they believe may be infested should seek medical attention promptly.
USDA has been consistent that the food supply is not affected. Screwworms infest living animals rather than meat, produce, or other food products, and inspection systems are designed to keep infested animals out of the supply.
Sterile Fly Releases and the Road Ahead
The eradication tool is the same one that worked when screwworm was driven out of the United States in 1966. Tens of millions of sterile flies are released in affected areas, and because females mate once, sterile pairings collapse reproduction over successive generations.
The method has a built-in lag that explains why new cases appear even in areas under treatment. Sterile insect technique does not kill existing larvae, and a fly's life cycle runs roughly three weeks, so multiple reproductive cycles must pass before wild populations decline. Announcing the first U.S. detection, Under Secretary for Marketing and Regulatory Programs Dudley Hoskins said: "protecting our livestock industry is a national security issue of the utmost importance." USDA is also expanding sterile fly capacity, including a $25 million commitment for a dispersal facility in Arizona announced in late July.
Trade policy is moving on a separate track. Under USDA's phased port reopening plan, the Douglas, Arizona port will reopen to livestock trade on August 24, with Santa Teresa and Columbus, New Mexico considered afterward. The agency has said reopening may be paused if risk assessments change.
APHIS updates its detection dashboard regularly. MedicalDaily will report on new infested zones, changes in the active case count, and any detection outside Texas and New Mexico.
Key Questions Answered
What is new in this report? A detection in sheep in Terrell County triggered a new Texas infested zone with movement restrictions, and the national count reached 45 detections with only five still active.
What is the difference between 45 and five? The 45 figure counts every confirmed detection since the first case in June. The five figure counts animals still requiring treatment and wound management right now.
Where are the restrictions? Movement restrictions now cover parts of more than 20 Texas counties, from the Rio Grande Valley through West Texas and the Hill Country. The Texas Animal Health Commission maintains a searchable map.
Is the meat supply affected? No. USDA says screwworm infests living animals rather than meat or produce, and inspection systems keep infested animals out of the food supply.
Can people get screwworm? It is uncommon. CDC assesses human risk as low and reports no domestically acquired human cases in this outbreak. Anyone with a suspicious wound should seek medical attention.
What should animal owners look for? Draining or enlarging wounds, signs of discomfort, and larvae or eggs near the nose, ears, genitalia, or a newborn animal's navel. Check after injuries, branding, or surgery.
Who do I call? In Texas, the Texas Animal Health Commission at 1-800-550-8242. Elsewhere, a veterinarian and your state animal health official.
