The U.S. Department of Agriculture confirmed June 3 that a case of the New World screwworm, a parasitic fly, was detected on a cattle ranch in South Texas.
The case marks the first domestic detection of screwworm in a decade and the first Texas case in approximately 50 years. The flesh-eating parasite is a threat to the state’s $15.5 billion cattle industry, which lost more than $132 million due to a 1976 outbreak.
No additional infestations have been identified, U.S. Secretary of Agriculture Brooke Rollins told reporters around 2 p.m. June 4. Federal and state officials have emphasized that they do not anticipate issues with the food supply chain, as the screwworm only targets live animals and does not infest meat, fruit or vegetables.
However, experts have warned that a larger, prolonged screwworm outbreak could cause a spike in beef prices. A widespread infestation is estimated to cost Texas at least $1.8 billion per year in damages, according to a USDA analysis of a 1976 screwworm outbreak.
Keep reading for more details about the June 3 case and the concerns the screwworm presents for the cattle industry.
The big picture
The New World Screwworm is a parasitic fly that is attracted to fresh wounds in live, warm-blooded animals, including cattle, sheep, pets, wildlife and sometimes humans. After a female screwworm fly lays eggs, maggots hatch and burrow into the flesh of living animals, according to the Texas A&M AgriLife Extension.
The infected animal is a 3-week-old calf in La Pryor, the USDA reported. The South Texas community is about a one-and-a-half-hour drive from San Antonio and less than an hour from Eagle Pass on the Texas-Mexico border.
“This is a serious animal health threat, particularly for Texas, but it is not a food safety issue and ranchers and landowners should not panic,” Stephen Diebel, president of the Texas & Southwestern Cattle Raisers Association, said in a June 3 statement.
The USDA established a 20-kilometer “infested zone” around the detection site with quarantines and movement controls in the area, officials said. There are no other confirmed cases, and more information about the federal and state response to the infestation is available here.
“If we all work together and follow animal treatment and the movement restriction guidance, there is no reason to believe that this incursion will result in any sort of establishment of the pest,” Rollins said during a June 4 news conference. “It is really important … for us to contain the pest in the limited area we’re talking about without disrupting too much commerce and too much of our livestock producers’ ability to make a living.”
Zooming in
Federal and state officials told reporters June 4 that the screwworm will not cause any immediate food supply issues, as the case is contained. The New World screwworm feeds on live animals and does not infect meat or other food sources.
“The food supply is not compromised at all. This is not a disease, it is not a virus,” Rollins said. “Once that larva is removed and the wound is clean, animals treated early enough will survive, will recover, and will be back to normal.”
Texas Agriculture Commissioner Sid Miller said he was concerned that Texas beef prices would rise as ranches are quarantined in the infested zone.
“We already have a shortage of beef,” Miller told Community Impact. “This is going to create, possibly, a [larger] shortage. Probably, the markets will crash and then afterwards they’re going to spike extremely high, because what will happen is these ranches will get quarantined and they can’t sell the cattle, so that’s less cattle available for the market.”
Miller has criticized the federal government’s response to the screwworm threat, urging the USDA to use certain pesticides to kill the flies in addition to existing eradication efforts.
Natalie Stewart, an assistant professor with Texas A&M University’s Department of Agricultural Economics, said she did not anticipate changes in the beef supply chain; however, production costs may rise for cattle farms.
“The significant impact for cattle producers in the short term will be to production costs,” she said in a statement to Community Impact. “Added production costs will come from the additional time, labor, and medicine needed to closely monitor and treat animals (either preventatively or in response to screwworm detection).”
Looking ahead
A widespread screwworm outbreak could cost Texas more than $1.8 billion, the USDA estimated in 2024. Texas cattle, sheep and goat producers would face about $732 million in annual losses.
Screwworm was eradicated in the U.S. in 1966, although the parasite reemerged in parts of the country, including in Texas, in the 1970s. A 1976 outbreak in Texas cost the state nearly $330 million, according to the USDA.
U.S. producers have not treated livestock for screwworm in about 40 years. Industry leaders urged Texans to keep a close eye on their livestock, pets and nearby wildlife to ensure the infestation does not spread.
“Texas livestock producers and all Texans must now be vigilant in their efforts to manage and combat the invasive pest,” Texas Farm Bureau President Russell Boening said in a June 3 statement.
The Texas Animal Health Commission is leading the charge on the June 3 case with support from the federal government, officials said. Information about monitoring, quarantines and how to report a potential screwworm case is available on the commission’s website.