Key facts
- Twelve animal cases of screwworm have been confirmed in the US, primarily in Texas and New Mexico.
- The screwworm is a fly larva that feeds on living tissue of warm-blooded animals.
- The parasite was largely eradicated in the US in the 1970s and its re-emergence is concerning.
- USDA officials are urging animal owners to watch for signs of infection and report suspected cases.
- The US food supply remains safe as the screwworm does not infest meat products.
- Texas is advocating for the use of the Screwworm Adult Suppression System (Swass) and sterile fly releases.
Screwworm cases are on the rise in the United States, with the outbreak now spreading beyond its initial contamination zones. Twelve animal cases have been confirmed, a significant increase from the first detection in a calf in south Texas on June 3. The growing number of infections has alarmed agricultural experts, who warn that a wider outbreak could have serious consequences for the Texas beef industry.
According to an update from the US Department of Agriculture’s animal and plant health inspection service, 11 of the 12 reported cases remain active, with one inactive. The most recent case was identified on June 12 in Sutton County, west Texas, involving a sheep. Other infections have been found in Edwards, Tom Green, Gillespie, La Salle, and Zavala counties in Texas, as well as Lea County, New Mexico. The affected animals include cattle, goats, sheep, and one dog.
The screwworm is a fly larva that burrows into open wounds on livestock and other warm-blooded animals, feeding on living tissue. The parasite was largely eradicated in the US in the 1970s and had been rarely seen for nearly six decades. Its re-emergence and rapid spread have raised concerns about its comeback, particularly as beef prices are at record highs.
USDA officials are urging animal owners to be vigilant for signs of screwworm infection, such as draining wounds, maggots, unusual discomfort, and lesions around sensitive areas. Suspected cases should be reported immediately to aid containment efforts. The USDA has assured that the US food supply remains safe, as the screwworm does not infest meat or produce.
Texas Agriculture Commissioner Sid Miller has warned of the spread, calling for the deployment of the Screwworm Adult Suppression System (Swass), a USDA program using targeted bait to kill fertile adult flies. He emphasized a strategy combining sterile fly releases with baiting to control the population. US Agriculture Secretary Brooke Rollins announced that 4 million sterile flies have been released both by air and on the ground to combat the outbreak.
Despite the outbreak being currently restricted to Texas and New Mexico, Pennsylvania’s agriculture department has implemented a precautionary quarantine order. This order imposes stricter controls on importing susceptible livestock from affected areas, requiring veterinary inspections and health documentation to mitigate the risk of the screwworm spreading into the state. Pennsylvania officials stated these proactive measures aim to protect farms and communities.