July 30, 2025

 

New World Screwworm feared to be next livestock epidemic 

 

After bird flu which led to the culling of large swaths of the US poultry flocks and set egg prices soaring, ranchers in Texas and officials at the US Agriculture Department are raising the next alarm: the New World screwworm.

 

Texas livestock producers and ranchers fear the United States is ill-equipped to handle a potential outbreak of screwworm, whose incursion into the country appears increasingly likely. With beef prices already soaring, the screwworm, whose Latin name roughly translates to "man-eater," is a real threat, to both cows and the cost of living for America's meat lovers.

 

"If we wait, we lose," Stephen Diebel, vice president of the Texas and Southwestern Cattle Raisers Association, told state lawmakers during a hearing in Austin earlier this month as he pleaded for intervention.

 

The screwworm, like the measles, may have been forgotten by many, but it's not new. And like the measles, which has cropped up in Texas recently, screwworm was once all but eradicated from the United States.

 

Infestations occur when a female fly lays eggs, between 10 and 400 at a time, on a fresh animal wound. Within a few hours, the eggs hatch into larvae that burrow and feed on the flesh. As the wound worsens, it attracts more flies, which lay more eggs. After about a week, adult screwworm flies can reproduce and begin the cycle all over again. The parasitic infection can kill a cow within two weeks if left untreated. There is currently no approved treatment.

 

"It's like something out of a horror movie," the Texas agriculture commissioner, Sid Miller, said in an interview. He saw distressed cattle infested with screwworm when he was a child in the early 1960s before it was nearly eradicated. "It's quite a putrid sight," he said.

 

Livestock, wildlife, pets and in rare cases, humans, can be affected.

 

In the 1950s, scientists discovered that radiation effectively sterilizes screwworm flies, and the federal government began an eradication programme. A small outbreak in a deer population in the Florida Keys was snuffed out in 2017.

  

Now, a potentially bigger threat is approaching, migrating north from South America, where screwworm is endemic. It has been detected as close as 370 miles from Texas' border, carried by the surge of animals coming through the Darién Gap, a once largely impenetrable jungle area that separates South and Central America. A joint eradication effort between the United States and Panama has largely kept screwworm south of Central America for decades. Illegal livestock transport and warm weather patterns have also contributed to the worm's climb north, a spokesman for the Agriculture Department said.

 

"For small herds, it could wipe us out," said Shelbie Pippenger, who, with her husband, has a small herd in Texas and helps manage other ranches. "Once something starts, it's difficult to stop it."

 

The agriculture secretary, Brooke Rollins, announced in June an US$8.5 million initiative based in Texas that will produce sterile male screwworm flies and then drop them into affected areas. Female flies mate only once in their lifetime, so the sterile flies eventually overwhelm and eradicate the pest.

 

Rollins also committed US$21 million to renovate a fly production facility in Mexico, where 60 million to 100 million sterile male flies would be produced each week for use in Mexico or Texas by the end of the year.

 

But that effort would yield only about 20% of the sterile flies the United States would need to manage an outbreak, experts said. Around 600 million flies were released each week to eradicate screwworm decades ago. Senator John Cornyn, Republican of Texas, introduced legislation that would provide US$300 million to construct a facility to breed and sterilise flies, but the House has left Washington for the summer.

-      New York Times